JoVE Visualize What is visualize?
Stop Reading. Start Watching.
Advanced Search
Stop Reading. Start Watching.
Regular Search
Find video protocols related to scientific articles indexed in Pubmed.
PERK-dependent activation of JAK1 and STAT3 contributes to endoplasmic reticulum stress-induced inflammation.
Mol. Cell. Biol.
PUBLISHED: 08-11-2014
Show Abstract
Hide Abstract
Neuroinflammation and endoplasmic reticulum (ER) stress are associated with many neurological diseases. Here, we have examined the interaction between ER stress and JAK/STAT-dependent inflammation in glial cells. We show that ER stress is present in the central nervous system (CNS) concomitant with inflammation and astrogliosis in the multiple sclerosis (MS) mouse model of experimental autoimmune encephalomyelitis (EAE). Astrocytes do not easily succumb to ER stress but rather activate an inflammatory program involving activation of STAT3 in a JAK1-dependent fashion. ER stress-induced activation of the JAK1/STAT3 axis leads to expression of interleukin 6 (IL-6) and several chemokines. Moreover, the activation of STAT3 signaling is dependent on PERK, a central component of the ER stress response, which we show is phosphorylated by JAK1. Disruption of PERK abrogates ER stress-induced activation of STAT3 and subsequent gene expression. Additionally, ER-stressed astrocytes, via paracrine signaling, can stimulate activation of microglia, leading to production of IL-6 and oncostatin M (OSM). These IL-6 cytokines can then synergize with ER stress in astrocytes to drive inflammation. Together, this work describes a new PERK/JAK1/STAT3 signaling pathway that elicits a feed-forward inflammatory loop involving astrocytes and microglia to drive neuroinflammation, which may be relevant in diseases such as MS.
Related JoVE Video
The low-temperature form of calcium gold stannide, CaAuSn.
Acta Crystallogr C Struct Chem
PUBLISHED: 06-17-2014
Show Abstract
Hide Abstract
The EuAuGe-type CaAuSn phase has been synthesized and single-crystal X-ray diffraction analysis reveals that it has an orthorhombic symmetry (space group Imm2), with a = 4.5261?(7)?Å, b = 7.1356?(11)?Å and c = 7.8147?(11)?Å. The structure features puckered layers that are connected by homoatomic Au-Au and Sn-Sn interlayer bonds. This structure is one of the two parent structures of its high-temperature polymorph (ca 873?K), which is an intergrowth structure of the EuAuGe- and SrMgSi-type structures in a 2:3 ratio.
Related JoVE Video
Ordered BaAl4-type variants in the BaAu(x)Sn(4-x) system: a unified view on their phase stabilities versus valence electron counts.
Inorg Chem
PUBLISHED: 05-28-2014
Show Abstract
Hide Abstract
Three ordered structures of the tetragonal BaAl4 type were identified in the Ba-Au-Sn system, from which a unified view of the interplay between the valence electron counts (VECs) and phase stabilities of these three types of derivatives can be developed. The BaNiSn3 (I4mm), ThCr2Si2 (I4/mmm), and CaBe2Ge2 (P4/nmm) type BaAu(x)Sn(4-x) phases occurred respectively at x = 0.78(1)-1, 1.38(1)-1.47(1), and 1.52(1)-2.17(1), consistent with theoretical atomic "coloring" analyses that reveal an optimal VEC of ?14 for the ThCr2Si2 type but larger and smaller values respectively for the BaNiSn3- and CaBe2Ge2-type structures.
Related JoVE Video
Neuronostatin inhibits glucose-stimulated insulin secretion via direct action on the pancreatic ?-cell.
Am. J. Physiol. Endocrinol. Metab.
PUBLISHED: 04-15-2014
Show Abstract
Hide Abstract
Neuronostatin is a recently described peptide hormone encoded by the somatostatin gene. We previously showed that intraperitoneal injection of neuronostatin into mice resulted in c-Jun accumulation in pancreatic islets in a pattern consistent with the activation of glucagon-producing ?-cells. We therefore hypothesized that neuronostatin could influence glucose homeostasis via a direct effect on the ?-cell. Neuronostatin enhanced low-glucose-induced glucagon release in isolated rat islets and in the immortalized ?-cell line ?TC1-9. Furthermore, incubation with neuronostatin led to an increase in transcription of glucagon mRNA, as determined by RT-PCR. Neuronostatin also inhibited glucose-stimulated insulin secretion from isolated islets. However, neuronostatin did not alter insulin release from the ?-cell line INS 832/13, indicating that the effect of neuronostatin on insulin secretion may be secondary to a direct action on the ?-cell. In agreement with our in vitro data, intra-arterial infusion of neuronostatin in male rats delayed glucose disposal and inhibited insulin release during a glucose challenge. These studies suggest that neuronostatin participates in maintaining glucose homeostasis through cell-cell interactions between ?-cells and ?-cells in the endocrine pancreas, leading to attenuation in insulin secretion.
Related JoVE Video
Nitric oxide induces ataxia telangiectasia mutated (ATM) protein-dependent ?H2AX protein formation in pancreatic ? cells.
J. Biol. Chem.
PUBLISHED: 03-07-2014
Show Abstract
Hide Abstract
In this study, the effects of cytokines on the activation of the DNA double strand break repair factors histone H2AX (H2AX) and ataxia telangiectasia mutated (ATM) were examined in pancreatic ? cells. We show that cytokines stimulate H2AX phosphorylation (?H2AX formation) in rat islets and insulinoma cells in a nitric oxide- and ATM-dependent manner. In contrast to the well documented role of ATM in DNA repair, ATM does not appear to participate in the repair of nitric oxide-induced DNA damage. Instead, nitric oxide-induced ?H2AX formation correlates temporally with the onset of irreversible DNA damage and the induction of apoptosis. Furthermore, inhibition of ATM attenuates cytokine-induced caspase activation. These findings show that the formation of DNA double strand breaks correlates with ATM activation, irreversible DNA damage, and ATM-dependent induction of apoptosis in cytokine-treated ? cells.
Related JoVE Video
Luminol-based chemiluminescent signals: clinical and non-clinical application and future uses.
Appl. Biochem. Biotechnol.
PUBLISHED: 03-06-2014
Show Abstract
Hide Abstract
Chemiluminescence (CL) is an important method for quantification and analysis of various macromolecules. A wide range of CL agents such as luminol, hydrogen peroxide, fluorescein, dioxetanes and derivatives of oxalate, and acridinium dyes are used according to their biological specificity and utility. This review describes the application of luminol chemiluminescence (LCL) in forensic, biomedical, and clinical sciences. LCL is a very useful detection method due to its selectivity, simplicity, low cost, and high sensitivity. LCL has a dynamic range of applications, including quantification and detection of macro and micromolecules such as proteins, carbohydrates, DNA, and RNA. Luminol-based methods are used in environmental monitoring as biosensors, in the pharmaceutical industry for cellular localization and as biological tracers, and in reporter gene-based assays and several other immunoassays. Here, we also provide information about different compounds that may enhance or inhibit the LCL along with the effect of pH and concentration on LCL. This review covers most of the significant information related to the applications of luminol in different fields.
Related JoVE Video
?-cell responses to nitric oxide.
Vitam. Horm.
PUBLISHED: 02-25-2014
Show Abstract
Hide Abstract
Autoimmune diabetes is characterized by the selective destruction of insulin-secreting ?-cells that occurs during an inflammatory reaction in and around pancreatic islets of Langerhans. Cytokines such as interleukin-1, released by activated immune cells, have been shown to inhibit insulin secretion from pancreatic ?-cells and cause islet destruction. In response to cytokines, ?-cells express inducible nitric oxide synthase and produce micromolar levels of the free radical nitric oxide. Nitric oxide inhibits the mitochondrial oxidation of glucose resulting in an impairment of insulin secretion. Nitric oxide is also responsible for cytokine-mediated DNA damage in ?-cells. While nitric oxide mediates the inhibitory and toxic effects of cytokines, it also activates protective pathways that allow ?-cells to recover from this damage. This review will focus on the dual role of nitric oxide as a mediator of cytokine-induced damage and the activator of repair mechanisms that protect ?-cells from cytokine-mediated injury.
Related JoVE Video
Proteoform analysis of lipocalin-type prostaglandin D-synthase from human cerebrospinal fluid by isoelectric focusing and superficially porous liquid chromatography with Fourier transform mass spectrometry.
Proteomics
PUBLISHED: 02-11-2014
Show Abstract
Hide Abstract
Lipocalin-type prostaglandin D-synthase (L-PGDS) in cerebrospinal fluid contributes to the maturation and maintenance of the CNS. L-PGDS PTMs may contribute to pathobiology of different CNS diseases, but methods to monitor its proteoforms are limited. Herein, we combined off-gel IEF and superficially porous LC (SPLC) with Fourier transform MS to characterize common cerebrospinal fluid L-PGDS proteoforms. Across 3D physiochemical space (pI, hydrophobicity, and mass), 217 putative proteoforms were observed from 21 to 24 kDa and pI 5-10. Glycoprotein accurate mass information, combined with MS/MS analysis of peptides generated from 2D-fractionated proteoforms, enabled the putative assignment of 208 proteoforms with varied PTM positional occupants. Fifteen structurally related N-glycans at N29 and N56 were observed, with different N-glycan compositional variants being preferred on each amino acid. We also observed that sialic acid content was a major factor for pI shifts between L-PGDS proteoforms. Other putative PTMs characterized include a core-1 HexHexNAc-O-glycan at S7, acetylation at K16 and K138, sulfonation at S41 and T142, and dioxidation at C43 and C145. The IEF-SPLC-MS platform presented provides 30-40× improved peak capacity versus conventional 2DE and shows potential for repeatable proteoform analysis of surrogate PTM-based biomarkers.
Related JoVE Video
MgAuGa and MgAu2Ga: first representatives of the Mg-Au-Ga system.
Acta Crystallogr C Struct Chem
PUBLISHED: 01-24-2014
Show Abstract
Hide Abstract
MgAuGa (magnesium gold gallium), the first ternary representative of the Mg-Au-Ga system, crystallizes in the space group P62m and adopts the Fe2P structure type (Pearson symbol hP9). Various phases with the general composition AB2 have been reported in the surrounding binary systems, viz. Mg2Ga (hP18), MgGa2 (hP6; CaIn2 type), AuGa2 (cF12; CaF2 type), Au2Ga (oS24; Pd2As type) and Mg2Au (oP12; Co2Si type). In principle, MgAuGa can be obtained from each of them by partial replacement of the major element with the missing element. In fact, the structure of MgAuGa closely resembles hexagonal Mg2Ga through a direct group-subgroup relationship. MgAu2Ga (magnesium digold gallium) also crystallizes hexagonally in the space group P6(3)/mmc and is isotypic with Na3As. It adopts the structure of another binary compound, viz. Mg3Au (hP8), but shows an unexpected distribution of Mg, Au, and Ga among the atomic positions of the asymmetric unit. Both MgAuGa and MgAu2Ga can be described as formally anionic Au/Ga frameworks, with pseudo-hexagonal tunnels around Mg in MgAuGa or cages in MgAu2Ga.
Related JoVE Video
Enhanced MIN-6 beta cell survival and function on a nitric oxide-releasing peptide amphiphile nanomatrix.
Int J Nanomedicine
PUBLISHED: 01-01-2014
Show Abstract
Hide Abstract
Innovative biomaterial strategies are required to improve islet cell retention, viability, and functionality, and thereby obtain clinically successful outcomes from pancreatic islet cell transplantation. To address this need, we have developed a peptide amphiphile-based nanomatrix that incorporates multifunctional bioactive cues and sustained release of nitric oxide. The goal of this study was to evaluate the effect of this peptide amphiphile nanomatrix on the viability and functionality of MIN-6 islet cells. Additionally, this study provides insight into the role of nitric oxide in islet cell biology, given that conventional nitric oxide donors are unable to release nitric oxide in a controlled, sustained manner, leading to ambiguous results. It was hypothesized that controlled nitric oxide release in synergy with multifunctional bioactive cues would promote islet cell viability and functionality. Nitric oxide-releasing peptide amphiphile nanomatrices within the range of 16.25 ?mol to 130 ?mol were used to analyze MIN-6 cell behavior. Both 32.5 ?mol and 65 ?mol peptide amphiphiles showed improved MIN-6 functionality in response to glucose over a 7-day time period, and the elevated functionality was correlated with both PDX-1 and insulin gene expression. Our results demonstrate that nitric oxide has a beneficial effect on MIN-6 cells in a concentration-dependent manner.
Related JoVE Video
Inducible HSP70 Regulates Superoxide Dismutase-2 and Mitochondrial Oxidative Stress in the endothelial cells from Developing Lungs.
Am. J. Physiol. Lung Cell Mol. Physiol.
PUBLISHED: 12-27-2013
Show Abstract
Hide Abstract
Superoxide dismutase 2 (SOD-2) is synthesized in the cytosol and imported into the mitochondrial matrix, where it is activated and functions as the primary antioxidant for cellular respiration. The specific mechanisms that target SOD-2 to the mitochondria remain unclear. We hypothesize that iHSP70 targets SOD2 to the mitochondria via a mechanism facilitated by ATP and this process is impaired in PPHN. We observed that iHSP70 interacts with SOD-2 and targets SOD-2 to the mitochondria. Interruption of iHSP70-SOD2 interactIon with 2-phenylethylenesulfonamide-mu (PFT-?, a specific inhibitor of substrate binding to iHSP70 C-terminus) and siRNA-mediated knockdown of iHSP70 expression disrupted SOD2 transport to mitochondria. Increasing intracellular ATP levels by stimulation of respiration with CaCl2 facilitated the mitochondrial import of SOD-2, increased SOD2 activity and decreased the mitochondrial superoxide (O2(•-)) levels in PPHN PAEC, by promoting iHSP70-SOD2 dissociation at the outer mitochondrial membrane. In contrast, oligomycin, an inhibitor of mitochondrial ATPase decreased SOD-2 expression and activity and increased O2(•-) levels in the mitochondria of control PAEC. The basal ATP levels and degree of iHSP70-SOD2 dissociation were lower in PPHN PAEC and lead to increased SOD-2 degradation in cytosol. In normal pulmonary arteries (PA), PFT-µ impaired the relaxation response of PA rings in response to nitric oxide (NO) donor, SNAP. Pretreatment with Mito-Q, a mitochondrial targeted O2(•-) scavenger restored the relaxation response in PA rings pretreated with PFT-µ. Our observations suggest that iHSP70 chaperones SOD-2 to the mitochondria. Impaired SOD2-iHSP70 dissociation decreases SOD-2 import and contributes to mitochondrial oxidative stress in PPHN.
Related JoVE Video
Gold Network Structures in Rhombohedral and Monoclinic Sr2Au6(Au,T)3 (T = Zn, Ga). A Transition via Relaxation.
Inorg Chem
PUBLISHED: 11-11-2013
Show Abstract
Hide Abstract
Quantitative syntheses, structure determinations and interpretations, and band calculations are reported for the nonstoichiometric rhombohedral (R3?c) and monoclinic (C2/c) Sr2Au6(Au3-xTx) (T = Zn, Ga) compounds. Several different compositions of the two Sr phases were similarly refined from single crystal X-ray diffraction data as R3?c: a ? 8.43 Å, c ? 21.85 Å, Z = 6 and C2/c: a ? 14.70 Å, b ? 8.47 Å, c ? 8.70 Å, ? ? 123.2°, Z = 4. The R3?c Zn phase is stable in the composition region x ? 2.5-2.9 whereas its C2/c neighbor is the major product at x ? 2.2-2.3. Gallium versions of both were also identified. Both R3?c and C2/c structural types contain hexagonal-diamond-like gold superlattices stuffed with strings of interstitial Sr and disordered triangular (Au,T)3 units. The latter space group is a maximal, nonisomorphic subgroup of the former, and the decrease in interstitial radius from Ba to Sr (?0.08 Å experimentally) evidently drives the symmetry reduction, relaxation, and small distortions, principally around the Sr sites. Au-Au bonding among the Au hexagons in the host lattices and with gold components in the triangular interstitials is dominant and reflected in their tight packing and short interatomic separations.
Related JoVE Video
Do ?-Cells Generate Peroxynitrite in Response to Cytokine Treatment?
J. Biol. Chem.
PUBLISHED: 11-05-2013
Show Abstract
Hide Abstract
The purpose of this study was to determine the reactive species that is responsible for cytokine-mediated ?-cell death. Inhibitors of inducible nitric oxide synthase prevent this death, and addition of exogenous nitric oxide using donors induces ?-cell death. The reaction of nitric oxide with superoxide results in the generation of peroxynitrite, and this powerful oxidant has been suggested to be the mediator of ?-cell death in response to cytokine treatment. Recently, coumarin-7-boronate has been developed as a probe for the selective detection of peroxynitrite. Using this reagent, we show that addition of the NADPH oxidase activator phorbol 12-myristate 13-acetate to nitric oxide-producing macrophages results in peroxynitrite generation. Using a similar approach, we demonstrate that cytokines fail to stimulate peroxynitrite generation by rat islets and insulinoma cells, either with or without phorbol 12-myristate 13-acetate treatment. When forced to produce superoxide using redox cyclers, this generation is associated with protection from nitric oxide toxicity. These findings indicate that: (i) nitric oxide is the likely mediator of the toxic effects of cytokines, (ii) ?-cells do not produce peroxynitrite in response to cytokines, and (iii) when forced to produce superoxide, the scavenging of nitric oxide by superoxide is associated with protection of ?-cells from nitric oxide-mediated toxicity.
Related JoVE Video
Polyclusters and substitution effects in the Na-Au-Ga system: remarkable sodium bonding characteristics in polar intermetallics.
Inorg Chem
PUBLISHED: 10-18-2013
Show Abstract
Hide Abstract
A systematic exploration of Na- and Au-poor parts of the Na-Au-Ga system (less than 15 at. % Na or Au) uncovered several compounds with novel structural features that are unusual for the rest of the system. Four ternary compounds Na1.00(3)Au0.18Ga1.82(1) (I), NaAu2Ga4 (II), Na5Au10Ga16 (III), and NaAu4Ga2 (IV) have been synthesized and structurally characterized by single crystal X-ray diffraction: Na1.00(3)Au0.18Ga1.82(1)(I, P6/mmm, a = 15.181(2), c =9.129(2)Å, Z = 30); NaAu2Ga4 (II, Pnma, a = 16.733(3), b = 4.3330(9), c =7.358(3) Å, Z = 4); Na5Au10Ga16 (III, P6(3)/m, a = 10.754(2), c =11.457(2) Å, Z = 2); and NaAu4Ga2 (IV, P2(1)/c, a = 8.292(2), b = 7.361(1), c =9.220(2)Å, ? = 116.15(3), Z = 4). Compound I lies between the large family of Bergman-related compounds and Na-poor Zintl-type compounds and exhibits a clathrate-like structure containing icosahedral clusters similar to those in cubic 1/1 approximants, as well as tunnels with highly disordered cation positions and fused Na-centered clusters. Structures II, III, and IV are built of polyanionic networks and clusters that generate novel tunnels in each that contain isolated, ordered Na atoms. Tight-binding electronic structure calculations using linear muffin-tin-orbital (LMTO) methods on II, III, IV and an idealized model of I show that all are metallic with evident pseudogaps at the Fermi levels. The integrated crystal orbital Hamilton populations for II-IV are typically dominated by Au-Ga, Ga-Ga, and Au-Au bonding, although Na-Au and Na-Ga contributions are also significant. Sodiums involvement into such covalency is consistent with that recently reported in Na-Au-M (M = Ga, Ge, Sn, Zn, and Cd) phases.
Related JoVE Video
Top-down mass spectrometry on tissue extracts and biofluids with isoelectric focusing and superficially porous silica liquid chromatography.
Anal. Chem.
PUBLISHED: 10-16-2013
Show Abstract
Hide Abstract
Top-down mass spectrometry (MS) has emerged as a powerful complement to peptide-based proteomics. Despite advancements, the field has had limited application to clinical proteomics investigations due to the complexity and poor dynamic range of chromatography used to separate intact proteins from tissue and biofluids. To address these limitations, we developed a two-dimensional (2D) chromatography platform that includes isoelectric focusing (IEF) through immobilized pH gradient and superficially porous liquid chromatography (SPLC). Analysis of standard proteins demonstrates compatibility of IEF-SPLC processing and high resolving-power MS analysis with results showing ~7.0 femtomole detection limits and linear spectral response for proteins fractionated over ~4 log sample loads. For proteins from heart myofibrils and cerebrospinal fluid (CSF), compared to one-dimensional SPLC-MS, the 2D IEF-SPLC-MS platform resulted in a 5-6× increase in the number of unique monoisotopic masses observed <30 kDa and an ~4× improved mass range enabling the observation of proteins >200 kDa. In the heart myofibrils, common protein proteoforms observed were associated with phosphorylation of contractile proteins with results showing that quantitative evaluation of their PTM stoichiometry was possible despite differentially modified forms being fractionated into separate pI compartments. In CSF, diverse protein mutations and PTM classes were also observed, including differentially glycosylated protein forms separated to different pI. Results also demonstrate that by the generation of IEF-SPLC protein libraries by fraction collection, the platform enables prospective protein identification and proteoform analysis investigations by complementary top-down and bottom-up strategies. Overall, the 2D platform presented may provide the speed, dynamic range, and detection limits necessary for routine characterization of proteoform-based biomarkers from biofluids and tissues.
Related JoVE Video
Immunoproteasome Activation During Early Antiviral Response in Mouse Pancreatic ?-cells: New Insights into Auto-antigen Generation in Type I Diabetes?
J Clin Cell Immunol
PUBLISHED: 08-20-2013
Show Abstract
Hide Abstract
Type 1 diabetes results from autoimmune destruction of the insulin producing pancreatic ?-cells. The immunoproteasome, a version of the proteasome that collaborates with the 11S/PA28 activator to generate immunogenic peptides for presentation by MHC class I molecules, has long been implicated in the onset of the disease, but little is known about immunoproteasome function and regulation in pancreatic ?-cells. Interesting insight into these issues comes from a recent analysis of the immunoproteasome expressed in pancreatic ?-cells during early antiviral defenses mediated by interferon ? (IFN?), a type I IFN implicated in the induction of the diabetic state in human and animal models. Using mouse islets and the MIN6 insulinoma cell line, Freudenburg et al. found that IFN? stimulates expression of the immunoproteasome and the 11S/PA28 activator in a manner fundamentally similar to the classic immuno-inducer IFN?, with similar timing of mRNA accumulation and decline; similar transcriptional activation mediated primarily by the IRF1 and similar mRNA and protein levels. Furthermore, neither IFN? nor IFN? altered the expression of regular proteolytic subunits or prevented their incorporation into proteolytic cores. As a result, immunoproteasomes had stochastic combinations of immune and regular proteolytic sites, an arrangement that would likely increase the probability with which unique immunogenic peptides are produced. However, immunoproteasomes were activated by the 11S/PA28 only under conditions of ATP depletion. A mechanism that prevents the activation of immunoproteasome at high ATP levels has not been reported before and could have a major regulatory significance, as it could suppress the generation of immunogenic peptides as cell accumulate immunoproteasome and 11S/PA28, and activate antigen processing only when ATP levels drop. We discuss implications of these new findings on the link between early antiviral response and the onset of type 1 diabetes.
Related JoVE Video
Substantial Cd-Cd bonding in Ca6PtCd11: a condensed intermetallic phase built of pentagonal Cd7 and rectangular Cd4/2Pt pyramids.
Inorg Chem
PUBLISHED: 08-19-2013
Show Abstract
Hide Abstract
The novel intermetallic Ca6PtCd11 is orthorhombic, Pnma, Z = 4, with a = 18.799(2) Å, b = 5.986(1) Å, c = 15.585(3) Å. The heavily condensed network contains three types of parallel cadmium chains: apically strongly interbonded Cd7 pentagonal bipyramids, linear Cd arrays, and rectangular Cd4/2Pt pyramids. All of the atoms have 11-13 neighbors. Calculations by means of the linear muffin-tin orbitals method in the atomic spheres approximation indicate that some Cd-Cd interactions correspond to notably high Hamilton populations (1.07 eV per average bond) whereas the Ca-Ca covalent interactions (integrated crystal orbital Hamiltonian population) are particularly small (0.17 eV/bond). (Pt-Cd interactions are individually greater but much less in aggregate.) The Ca-Ca separations are small, appreciably less than the single bond metallic diameters, and unusually uniform (? = 0.14 Å). The Cd atoms make major contributions to the stability of the phase via substantial 5s and 5p bonding, which include back-donation of Cd 5s, 5p and Pt 5d into Ca 3d states in the principal bonding modes for Ca-Cd and Ca-Pt. Bonding Ca-Ca, Ca-Cd, and Cd-Cd states remain above EF, and some relative oxidation of Ca in this structure seems probable. Ca6PtCd11 joins a small group of other phases in which Cd clustering and Cd-Cd bonding are important.
Related JoVE Video
Hexagonal-diamond-like gold lattices, Ba and (Au,T)3 interstitials, and delocalized bonding in a family of intermetallic phases Ba2Au6(Au,T)3 (T = Zn, Cd, Ga, In, or Sn).
J. Am. Chem. Soc.
PUBLISHED: 07-16-2013
Show Abstract
Hide Abstract
Au-rich polar intermetallics exhibit a wide variety of structural motifs, and this hexagonal-diamond-like gold host is unprecedented. The series Ba2Au6(Au,T)3 (T = Zn, Cd, Ga, In, or Sn), synthesized through fusion of the elements at 700-800 °C followed by annealing at 400-500 °C, occur in space group R3[overline]c (a ? 8.6-8.9 Å, c ? 21.9-22.6 Å, and Z = 6). Their remarkable structure, generated by just three independent atoms, features a hexagonal-diamond-like gold superstructure in which tunnels along the 3-fold axes are systematically filled by interstitial Ba atoms (blue) and triangles of disordered (Au,T)3 atoms (green) in 2:1 proportions. The Au/Zn mixing in the latter spans ~34 to 87% Zn, whereas the Au/Sn result is virtually invariant compositionally. Complementary bonding between the gold lattice and the disordered (Au,T)3 units is substantial and very regular. Bonding and charge density analyses indicate delocalized bonding within the gold host and the (Au,T)3 triangular units, and moderately polarized bonding between Ba and the electronegative framework. The new structure can also be viewed empirically as the result of an atom-by-triad [i.e., Ba by (Au,T)3 triangle] topological substitution in a BaAu2 (AlB2-type) superstructure.
Related JoVE Video
Effect of nitric oxide on naphthoquinone toxicity in endothelial cells: role of bioenergetic dysfunction and poly (ADP-ribose) polymerase activation.
Biochemistry
PUBLISHED: 06-14-2013
Show Abstract
Hide Abstract
When produced at physiological levels, reactive oxygen species (ROS) can act as signaling molecules to regulate normal vascular function. Produced under pathological conditions, ROS can contribute to the oxidative damage of cellular components (e.g., DNA and proteins) and trigger cell death. Moreover, the reaction of superoxide with nitric oxide (NO) produces the strong oxidant peroxynitrite and decreases NO bioavailability, both of which may contribute to activation of cell death pathways. The effects of ROS generated from the 1,4-naphthoquinones alone and in combination with NO on the activation status of poly(ADP-ribose) polymerase (PARP) and cell viability were examined. Treatment with redox cycling quinones activates PARP, and this stimulatory effect is attenuated in the presence of NO. Mitochondria play a central role in cell death signaling pathways and are a target of oxidants. We show that simultaneous exposure of endothelial cells to NO and ROS results in mitochondrial dysfunction, ATP and NAD(+) depletion, and cell death. Alone, NO and ROS have only minor effects on cellular bioenergetics. Further, PARP inhibition does not attenuate reduced cell viability or mitochondrial dysfunction. These results show that concomitant exposure to NO and ROS impairs energy metabolism and triggers PARP-independent cell death. While superoxide-mediated PARP activation is attenuated in the presence of NO, PARP inhibition does not modify the loss of mitochondrial function or adenine and pyridine nucleotide pools and subsequent bioenergetic dysfunction. These findings suggest that the mechanisms by which ROS and NO induce endothelial cell death are closely linked to the maintenance of mitochondrial function and not overactivation of PARP.
Related JoVE Video
Disorder-order structural transformation in electron-poor Sr3Au8Sn3 driven by chemical bonding optimization.
Inorg Chem
PUBLISHED: 05-16-2013
Show Abstract
Hide Abstract
Sr3Au8Sn3 was synthesized through fusion of a stoichiometric amount of pure metals at 800 °C and annealing treatments at lower temperatures. Single-crystal X-ray diffraction analyses revealed that Sr3Au8Sn3 has a La3Al11-type Immm structure (a = 4.6767(8) Å, b = 9.646(2) Å, c = 14.170(2) Å, Z = 2) if annealed at 550 °C and above but a Ca3Au8Ge3-type structure (Pnnm, a = 9.6082(8) Å, b = 14.171(1) Å, c = 4.6719(4) Å, Z = 2) if annealed at 400 °C. The transition occurs at about 454 °C according to DTA data. Both structures feature columns of Sr-centered pentagonal and hexagonal prisms of Au and Sn stacked along the respective longest axial directions, but different "colorings" of the polyhedra are evident. In the high-temperature phase (Immm) all sites shared between the two prisms adopt 50:50 mixtures of Au/Sn atoms, whereas in the low-temperature phase (Pnnm) Au or Sn are completely ordered. A Klassengleiche group-subgroup relationship was established between these two structures. LMTO-ASA calculations reveal that ?E for the disorder-to-order transformation on cooling is driven mainly by optimization of the Au-Au and Au-Sn bond populations around the former mixed Au/Sn sites, particularly those with extremely short bonds at the higher temperature. These gains also overcome the smaller effect of ordering on the entropy decrease.
Related JoVE Video
The autoimmunity-associated gene PTPN22 potentiates toll-like receptor-driven, type 1 interferon-dependent immunity.
Immunity
PUBLISHED: 04-24-2013
Show Abstract
Hide Abstract
Immune cells sense microbial products through Toll-like receptors (TLR), which trigger host defense responses including type 1 interferons (IFNs) secretion. A coding polymorphism in the protein tyrosine phosphatase nonreceptor type 22 (PTPN22) gene is a susceptibility allele for human autoimmune and infectious disease. We report that Ptpn22 selectively regulated type 1 IFN production after TLR engagement in myeloid cells. Ptpn22 promoted host antiviral responses and was critical for TLR agonist-induced, type 1 IFN-dependent suppression of inflammation in colitis and arthritis. PTPN22 directly associated with TNF receptor-associated factor 3 (TRAF3) and promotes TRAF3 lysine 63-linked ubiquitination. The disease-associated PTPN22W variant failed to promote TRAF3 ubiquitination, type 1 IFN upregulation, and type 1 IFN-dependent suppression of arthritis. The findings establish a candidate innate immune mechanism of action for a human autoimmunity "risk" gene in the regulation of host defense and inflammation.
Related JoVE Video
Improved MIN6 ?-cell function on self-assembled peptide amphiphile nanomatrix inscribed with extracellular matrix-derived cell adhesive ligands.
Macromol Biosci
PUBLISHED: 03-22-2013
Show Abstract
Hide Abstract
Understanding the role of the pancreatic extracellular matrix (ECM) in supporting islet survival and function drives the pursuit to create biomaterials that imitate and restore the pancreatic ECM microenvironment. To create an ECM mimic holding bioinductive cues for ?-cells, self-assembled peptide amphiphiles (PAs) inscribed with four selected ECM-derived cell adhesive ligands are synthesized. After 7 days, compared to control groups cultured on biologically inert substrates, MIN6 ?-cells cultured on PAs functionalized with YIGSR and RGDS cell adhesive ligands exhibit elevated insulin secretion in responses to glucose and also form ?-cell clusters. These findings suggest that the self-assembled PA nanomatrix may be utilized to improve pancreatic islet transplantation for treating type 1 diabetes.
Related JoVE Video
Ketamine enhances human neural stem cell proliferation and induces neuronal apoptosis via reactive oxygen species-mediated mitochondrial pathway.
Anesth. Analg.
PUBLISHED: 03-04-2013
Show Abstract
Hide Abstract
Growing evidence indicates that ketamine causes neurotoxicity in a variety of developing animal models, leading to a serious concern regarding the safety of pediatric anesthesia. However, if and how ketamine induces human neural cell toxicity is unknown. Recapitulation of neurogenesis from human embryonic stem cells (hESCs) in vitro allows investigation of the toxic effects of ketamine on neural stem cells (NSCs) and developing neurons, which is impossible to perform in humans. In the present study, we assessed the influence of ketamine on the hESC-derived NSCs and neurons.
Related JoVE Video
Cluster chemistry in electron-poor Ae-Pt-Cd systems (Ae = Ca, Sr, Ba): (Sr,Ba)Pt2Cd4, Ca6Pt8Cd16, and its known antitype Er6Pd16Sb8.
Inorg Chem
PUBLISHED: 02-18-2013
Show Abstract
Hide Abstract
Three new ternary polar intermetallic compounds, cubic Ca6Pt8Cd16, and tetragonal (Sr, Ba)Pt2Cd4 have been discovered during explorations of the Ae-Pt-Cd systems. Cubic Ca6Pt8Cd16 (Fm-3m, Z = 4, a = 13.513(1) Å) contains a 3D array of separate Cd8 tetrahedral stars (TS) that are both face capped along the axes and diagonally bridged by Pt atoms to generate the 3D anionic network Cd8[Pt(1)]6/2[Pt(2)]4/8. The complementary cationic surface of the cell consists of a face-centered cube of Pt(3)@Ca6 octahedra. This structure is an ordered ternary variant of Sc11Ir4 (Sc6Ir8Sc16), a stuffed version of the close relative Na6Au7Cd16, and a network inverse of the recent Er6Sb8Pd16 (compare Ca6Pt8Cd16). The three groups of elements each occur in only one structural version. The new AePt2Cd4, Ae = Sr, Ba, are tetragonal (P42/mnm,Z = 2, a ? 8.30 Å, c ? 4.47 Å) and contain chains of edge-sharing Cd4 tetrahedra along c that are bridged by four-bonded Ba/Sr. LMTO-ASA and ICOHP calculation results and comparisons show that the major bonding (Hamilton) populations in Ca6Pt8Cd16 and Er6Sb8Pd16 come from polar Pt-Cd and Pd-Sb interactions, that Pt exhibits larger relativistic contributions than Pd, that characteristic size and orbital differences are most evident for Sb 5s, Pt8, and Pd16, and that some terms remain incomparable, Ca-Cd versus Er-Pd.
Related JoVE Video
Reduction in ATP levels triggers immunoproteasome activation by the 11S (PA28) regulator during early antiviral response mediated by IFN? in mouse pancreatic ?-cells.
PLoS ONE
PUBLISHED: 02-01-2013
Show Abstract
Hide Abstract
Autoimmune destruction of insulin producing pancreatic ?-cells is the hallmark of type I diabetes. One of the key molecules implicated in the disease onset is the immunoproteasome, a protease with multiple proteolytic sites that collaborates with the constitutive 19S and the inducible 11S (PA28) activators to produce immunogenic peptides for presentation by MHC class I molecules. Despite its importance, little is known about the function and regulation of the immunoproteasome in pancreatic ?-cells. Of special interest to immunoproteasome activation in ?-cells are the effects of IFN?, a type I IFN secreted by virus-infected cells and implicated in type I diabetes onset, compared to IFN?, the classic immunoproteasome inducer secreted by cells of the immune system. By qPCR analysis, we show that mouse insulinoma MIN6 cells and mouse islets accumulate the immune proteolytic ?1(i), ?2(i) and ?5(i), and 11S mRNAs upon exposure to IFN? or IFN?. Higher concentrations of IFN? than IFN? are needed for similar expression, but in each case the expression is transient, with maximal mRNA accumulation in 12 hours, and depends primarily on Interferon Regulatory Factor 1. IFNs do not alter expression of regular proteasome genes, and in the time frame of IFN?-mediated response, the immune and regular proteolytic subunits co-exist in the 20S particles. In cell extracts with ATP, these particles have normal peptidase activities and degrade polyubiquitinated proteins with rates typical of the regular proteasome, implicating normal regulation by the 19S activator. However, ATP depletion rapidly stimulates the catalytic rates in a manner consistent with levels of the 11S activator. These findings suggest that stochastic combination of regular and immune proteolytic subunits may increase the probability with which unique immunogenic peptides are produced in pancreatic ?-cells exposed to IFN?, but primarily in cells with reduced ATP levels that stimulate the 11S participation in immunoproteasome function.
Related JoVE Video
The role of reactive oxygen species and proinflammatory cytokines in type 1 diabetes pathogenesis.
Ann. N. Y. Acad. Sci.
PUBLISHED: 01-16-2013
Show Abstract
Hide Abstract
Type 1 diabetes (T1D) is a T cell-mediated autoimmune disease characterized by the destruction of insulin-secreting pancreatic ? cells. In humans with T1D and in nonobese diabetic (NOD) mice (a murine model for human T1D), autoreactive T cells cause ?-cell destruction, as transfer or deletion of these cells induces or prevents disease, respectively. CD4(+) and CD8(+) T cells use distinct effector mechanisms and act at different stages throughout T1D to fuel pancreatic ?-cell destruction and disease pathogenesis. While these adaptive immune cells employ distinct mechanisms for ?-cell destruction, one central means for enhancing their autoreactivity is by the secretion of proinflammatory cytokines, such as IFN-?, TNF-?, and IL-1. In addition to their production by diabetogenic T cells, proinflammatory cytokines are induced by reactive oxygen species (ROS) via redox-dependent signaling pathways. Highly reactive molecules, proinflammatory cytokines are produced upon lymphocyte infiltration into pancreatic islets and induce disease pathogenicity by directly killing ? cells, which characteristically possess low levels of antioxidant defense enzymes. In addition to ?-cell destruction, proinflammatory cytokines are necessary for efficient adaptive immune maturation, and in the context of T1D they exacerbate autoimmunity by intensifying adaptive immune responses. The first half of this review discusses the mechanisms by which autoreactive T cells induce T1D pathogenesis and the importance of ROS for efficient adaptive immune activation, which, in the context of T1D, exacerbates autoimmunity. The second half provides a comprehensive and detailed analysis of (1) the mechanisms by which cytokines such as IL-1 and IFN-? influence islet insulin secretion and apoptosis and (2) the key free radicals and transcription factors that control these processes.
Related JoVE Video
Differential responses of pancreatic ?-cells to ROS and RNS.
Am. J. Physiol. Endocrinol. Metab.
PUBLISHED: 01-15-2013
Show Abstract
Hide Abstract
Reactive oxygen species (ROS) and reactive nitrogen species (RNS) direct the activation of distinct signaling pathways that determine cell fate. In this study, the pathways activated and the mechanisms by which ROS and RNS control the viability of pancreatic ?-cells were examined. Although both nitric oxide and hydrogen peroxide (H?O?) induce DNA damage, reduce cell viability, and activate AMPK, the mechanisms of AMPK activation and cell death induction differ between each reactive species. Nitric oxide activates the unfolded protein and heat shock responses and MAPK kinase signaling, whereas H?O? stimulates p53 stabilization and poly(ADP-ribose) polymerase (PARP) activation but fails to induce the unfolded protein or heat shock responses or MAPK activation. The control of cell fate decisions is selective for the form of stress. H?O?-mediated reduction in ?-cell viability is controlled by PARP, whereas cell death in response to nitric oxide is PARP independent but associated with the nuclear localization of GAPDH. These findings show that both ROS and RNS activate AMPK, induce DNA damage, and reduce cell viability; however, the pathways controlling the responses of ?-cells are selective for the type of reactive species.
Related JoVE Video
Y3MnAu5: three distinctive d-metal functions in an intergrown cluster phase.
J. Am. Chem. Soc.
PUBLISHED: 01-02-2013
Show Abstract
Hide Abstract
The new Y(3)MnAu(5) intermetallic phase is obtained from the arc-melted elements in virtually quantitative yields after annealing at 1000 °C for ~3 d. Its remarkable structure [rhombohedral, R3, Z = 6; a = 8.489(1) Å, c = 18.144(2) Å] consists of a 2:1 cubic-close-packed intergrowth between edge-shared Mn-centered Au rhombohedra (Mn@Au(8)) with gold-centered antiprismatic (Au@Y(6)) clusters via a common gold network. Magnetic susceptibility (?) data for Y(3)MnAu(5) were fitted by a Curie-Weiss law. The Curie constant indicates a large effective moment corresponding to nearly localized Mn spins S = 5/2, and the Weiss temperature demonstrates the dominance of ferromagnetic (FM) interactions. An antiferromagnetic (AFM) transition at T(N) = 75 K and a possible spin reorientation transition at 65 K were observed. Analysis of the ? data for T < T(N) suggests a planar noncollinear helical AFM structure that arises from competing AFM interactions between FM-aligned layers of spins in the ab-plane with a turn angle of 69° between the spins along the helix c-axis. A magnetic field-induced spin flop transition is observed below T(N). Spin-polarized LMTO-LSDA calculations indicate an ~2 eV splitting of the Mn 3d states and a metallic ground state, and their COHP analyses demonstrate that ~81% of the total Hamilton populations originate from heteroatomic polar Y-Au and Mn-Au bonding. The Mn 3d, Y 4d, and Au 5d characteristics are remarkably diverse: localized and magnetically polarized for Mn; reducing and cationic for Y; and relativistically strongly bonded and oxidizing for Au, bonding of the latter two being broadly delocalized.
Related JoVE Video
Sustained NF-?B Activation and Inhibition in ?-Cells Have Minimal Effects on Function and Islet Transplant Outcomes.
PLoS ONE
PUBLISHED: 01-01-2013
Show Abstract
Hide Abstract
The activation of the transcription factor NF-?B leads to changes in expression of many genes in pancreatic ?-cells. However, the role of NF-?B activation in islet transplantation has not been fully elucidated. The aim of the present study was to investigate whether the state of NF-?B activation would influence the outcome of islet transplantation. Transgenic mice expressing a dominant active IKK? (constitutively active) or a non-degradable form of I?B? (constitutive inhibition) under control of the rat insulin promoter were generated. Islets from these mice were transplanted into streptozotocin diabetic mice in suboptimal numbers. Further, the effects of salicylate (an inhibitor of NF-?B) treatment of normal islets prior to transplantation, and the effects of salicylate administration to mice prior to and after islet implantation were evaluated. Transplantation outcomes were not affected using islets expressing a non-degradable form of I?B? when compared to wild type controls. However, the transplantation outcomes using islets isolated from mice expressing a constitutively active mutant of NF-?B were marginally worse, although no aberrations of islet function in vitro could be detected. Salicylate treatment of normal islets or mice had no effect on transplantation outcome. The current study draws attention to the complexities of NF-?B in pancreatic beta cells by suggesting that they can adapt with normal or near normal function to both chronic activation and inhibition of this important transcription factor.
Related JoVE Video
Synthesis, structure, and bonding of orthorhombic R5Au2Te2 (R = Lu, Ho, Dy, Y). Electronic structure of the binary parent valence compound Eu5As4.
Inorg Chem
PUBLISHED: 10-12-2011
Show Abstract
Hide Abstract
Four examples of R(5)Au(2)Te(2) (vec = 29 e(-); R = Lu, Ho, Dy, Y) have been synthesized by high-temperature solid-state techniques, isotypic examples of Tm(5)Sb(2)Si(2) (vec = 33 e(-)) and binary Eu(5)As(4) (vec = 30 e(-)). The crystal structure was established for Lu(5)Au(2)Te(2), (orthorhombic Cmce (No. 64), a = 15.056(2), b = 7.749(1), c = 7.754(1) Å, and Z = 4), in which pairs of tellurium layers alternate with two-dimensional (2D) Lu(5)Au(2) slabs that are aggregated in such a way that each Au(2)-centered bi-trigonal prism (BTP) of Lu interconnects four other identical units, with the remaining cavities filled by nominal body-centered Lu cubes. The metal-metal aggregation in this structure provides a novel building unit in ternary rare-earth-metal-rich tellurides. Linear-muffin-tin-orbital (LMTO) electronic structure calculations and COHP analyses reveal that Lu(5)Au(2)Te(2) is a poor metal with Au(2) dimers and strong polar Lu-Au and Lu-Te interactions. The first theoretical analysis of the binary parent structure Eu(5)As(4) (vec = 30 e(-)) provides a simpler description of the equivalent orbital interactions and a closed shell gap in terms of the idealized (Eu(2+))(5)(As(2)(4-))(As(3-))(2) representation, particularly for the explicit filled As(2) levels ?(s), ?(s)*, ?(p), ?, ?*, plus empty ?(p)*. Crystal Orbital Hamilton Population (-COHP) data illuminate the prominent roles that polar bonding of Eu-As or Lu-Te and Lu-Au and relativistic effects with gold play in these, the former corresponding to 83% and 86% of the total Hamilton population for Eu(5)As(4) and Lu(5)Au(2)Te(2), respectively.
Related JoVE Video
Exploratory syntheses and structures of SrAu(4.3)In(1.7) and CaAg(3.5)In(1.9): electron-poor intermetallics with diversified polyanionic frameworks that are derived from the CaAu4In2 approximant.
Inorg Chem
PUBLISHED: 10-11-2011
Show Abstract
Hide Abstract
The phase regions around quasicrystals and approximants (QC/ACs) are rich pools for electron-poor intermetallics with novel, complex structures, and bonding patterns. The present SrAu(4.30(1))In(1.70(1)) (1) and CaAg(3.54(1))In(1.88(1)) (2) were synthesized through chemical tunings of the model CaAu(4)In(2) (YCd(6)-Type) AC. Single crystal X-ray diffraction analyses reveals that crystal 1 has Pnma (CeCu(6)-type) symmetry, with a = 9.102(1) Å, b = 5.6379(9) Å, and c = 11.515(2) Å. The building block in 1 is a 19-vertex cluster Sr@Au(9)In(4)M(6) (M = Au/In), which vividly mimics Ca@(Au,In)(18) in Ca(3)Au(12.4)In(6.1) (YCd(6)-type) in geometry. These clusters aggregate into one-dimensional columns extending along the b axis. Crystal 2 (P6/mmm, a = 20.660(3) Å, c = 9.410(2) Å) is closely related to Na(26)Cd(141) (hP167) and Y(13)Pd(40)Sn(31) (hP168), which are differentiated by the selective occupation of Wyckoff 1a (0 0 0) or 2d (1/3 2/3 1/2) sites by Cd or Pd. Crystal 2 adopts the Na(26)Cd(141) structure, but the 1a site is split into two partially occupied sites. The synergistic disorder in the hexagonal tunnels along c is a major property. The valence electron count per atom (e/a) values for 1 and 2 are 1.63 and 1.74, respectively, the lowest among any other ternary phases in each system. These values are close to those of ACs in the Ca-Au-M (M = Ga, In) systems. Electronic structures for both are discussed in terms of the results of TB-LMTO-ASA calculations.
Related JoVE Video
IRE1-dependent activation of AMPK in response to nitric oxide.
Mol. Cell. Biol.
PUBLISHED: 09-06-2011
Show Abstract
Hide Abstract
While there can be detrimental consequences of nitric oxide production at pathological concentrations, eukaryotic cells have evolved protective mechanisms to defend themselves against this damage. The unfolded-protein response (UPR), activated by misfolded proteins and oxidative stress, is one adaptive mechanism that is employed to protect cells from stress. Nitric oxide is a potent activator of AMP-activated protein kinase (AMPK), and AMPK participates in the cellular defense against nitric oxide-mediated damage in pancreatic ?-cells. In this study, the mechanism of AMPK activation by nitric oxide was explored. The known AMPK kinases LKB1, CaMKK, and TAK1 are not required for the activation of AMPK by nitric oxide. Instead, this activation is dependent on the endoplasmic reticulum (ER) stress-activated protein IRE1. Nitric oxide-induced AMPK phosphorylation and subsequent signaling to AMPK substrates, including Raptor, acetyl coenzyme A carboxylase, and PGC-1?, is attenuated in IRE1?-deficient cells. The endoribonuclease activity of IRE1 appears to be required for AMPK activation in response to nitric oxide. In addition to nitric oxide, stimulation of IRE1 endoribonuclease activity with the flavonol quercetin leads to IRE1-dependent AMPK activation. These findings indicate that the RNase activity of IRE1 participates in AMPK activation and subsequent signaling through multiple AMPK-dependent pathways in response to nitrosative stress.
Related JoVE Video
Ccr5 regulates inflammatory gene expression in response to encephalomyocarditis virus infection.
Am. J. Pathol.
PUBLISHED: 07-28-2011
Show Abstract
Hide Abstract
Encephalomyocarditis virus (EMCV) is capable of stimulating inflammatory gene expression by macrophages as a result of interactions between EMCV capsid proteins and cell surface receptors. In this study, biochemical and genetic approaches identified a role for Ccr5, a chemokine receptor, in transducing the signals of EMCV infection that result in the expression of inflammatory genes in macrophages. Antibody neutralization and gene knockout strategies were used to show that the presence of Ccr5 is required for EMCV-stimulated mitogen-activated protein (MAP) kinase and nuclear factor-kappa B (NF-?B) activation, and the subsequent expression of the inflammatory gene-inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2). Ccr5 appears to participate in the early control of virus replication: EMCV mRNA accumulates to sevenfold higher levels in Ccr5-deficient mice when compared to wild-type controls. These findings support a regulatory role for Ccr5 in the antiviral response to EMCV in which this chemokine receptor participates in regulation of inflammatory gene expression in response to virus infection.
Related JoVE Video
Two new compounds, ?-ScTe and Y3Au2, and a reassessment of Y2Au.
Acta Crystallogr C
PUBLISHED: 07-27-2011
Show Abstract
Hide Abstract
Two new compounds, ?-ScTe (scandium telluride) and Y(3)Au(2) (triyttrium digold), have been synthesized by high-temperature solid-state techniques and their crystal structures, along with that of Y(2)Au (diyttrium gold), have been refined by single-crystal X-ray diffraction methods. ?-ScTe is a superstructure of ScTe (NiAs-type), featuring double hexagonal close-packed layers of Te atoms with the octahedral cavities filled by Sc atoms. Y(3)Au(2) displays a U(3)Si(2)-type structure and is built from Au(2)-centered bitrigonal prisms and centered cubes of Y atoms. The structure of Y(2)Au is better described as an inverse PbCl(2)-type structure rather than a Co(2)Si-type.
Related JoVE Video
Relativistic effects and gold site distributions: synthesis, structure, and bonding in a polar intermetallic Na6Cd16Au7.
Inorg Chem
PUBLISHED: 07-05-2011
Show Abstract
Hide Abstract
Na(6)Cd(16)Au(7) has been synthesized via typical high-temperature reactions, and its structure refined by single crystal X-ray diffraction as cubic, Fm ?3m, a = 13.589(1) Å, Z = 4. The structure consists of Cd(8) tetrahedral star (TS) building blocks that are face capped by six shared gold (Au2) vertexes and further diagonally bridged via Au1 to generate an orthogonal, three-dimensional framework [Cd(8)(Au2)(6/2)(Au1)(4/8)], an ordered ternary derivative of Mn(6)Th(23). Linear muffin-tin-orbital (LMTO)-atomic sphere approximation (ASA) electronic structure calculations indicate that Na(6)Cd(16)Au(7) is metallic and that ?76% of the total crystal orbital Hamilton populations (-ICOHP) originate from polar Cd-Au bonding with 18% more from fewer Cd-Cd contacts. Na(6)Cd(16)Au(7) (45 valence electron count (vec)) is isotypic with the older electron-richer Mg(6)Cu(16)Si(7) (56 vec) in which the atom types are switched and bonding characteristics among the network elements are altered considerably (Si for Au, Cu for Cd, Mg for Na). The earlier and more electronegative element Au now occupies the Si site, in accord with the larger relativistic bonding contributions from polar Cd-Au versus Cu-Si bonds with the neighboring Cd in the former Cu positions. Substantial electronic differences in partial densities-of-states (PDOS) and COHP data for all atoms emphasize these. Strong contributions of nearby Au 5d(10) to bonding states without altering the formal vec are the likely origin of these effects.
Related JoVE Video
Ca14Au46Sn5: a "colored" Gd14Ag51-type structure containing columns of well-differentiated hexagonal gold stars.
Inorg Chem
PUBLISHED: 01-21-2011
Show Abstract
Hide Abstract
A novel hexagonal phase discovered near the Ca(15)Au(60)Sn(25) quasicrystal and its cubic approximants (ACs) was synthesized by means of high-temperature solid-state reactions. Single-crystal structural analyses show that this is a Gd(14)Ag(51) isotype with composition within the range Ca(14)Au(45.56(4)-46.67(4))Sn(5.14(3)-4.14(3)), space group P6/m (No. 175), and lattice parameters a = 12.763(3)-12.879(3) Å and c = 9.326(3)-9.3815(4) Å. In this phase, Sn mixes with Au in two of seven anionic sites to give a strong coloring that generates a narrow honeycomb-like Au/Sn template, in which sizable columns of hexagonal Au stars are confined. This phase transforms into the cubic 2/1 AC phase through a peritectic reaction at ?678 °C. The valence electron count per atom (e/a) of the present phase is in the range 1.41-1.45. However, it does not appear to follow a Hume-Rothery mechanism.
Related JoVE Video
FoxO1 and SIRT1 regulate beta-cell responses to nitric oxide.
J. Biol. Chem.
PUBLISHED: 01-01-2011
Show Abstract
Hide Abstract
For many cell types, including pancreatic ?-cells, nitric oxide is a mediator of cell death; paradoxically, nitric oxide can also activate pathways that promote the repair of cellular damage. In this report, a role for FoxO1-dependent transcriptional activation and its regulation by SIRT1 in determining the cellular response to nitric oxide is provided. In response to nitric oxide, FoxO1 translocates from the cytoplasm to the nucleus and stimulates the expression of the DNA repair gene GADD45?, resulting in FoxO1-dependent DNA repair. FoxO1-dependent gene expression appears to be regulated by the NAD(+)-dependent deacetylase SIRT1. In response to SIRT1 inhibitors, the FoxO1-dependent protective actions of nitric oxide (GADD45? expression and DNA repair) are attenuated, and FoxO1 activates a proapoptotic program that includes PUMA (p53-up-regulated mediator of apoptosis) mRNA accumulation and caspase-3 cleavage. These findings support primary roles for FoxO1 and SIRT1 in regulating the cellular responses of ?-cells to nitric oxide.
Related JoVE Video
Synthesis, structure, and bonding of BaTl4. Size effects on encapsulation of cations in electron-poor metal networks.
Inorg Chem
PUBLISHED: 12-07-2010
Show Abstract
Hide Abstract
The synthesis, structure, and bonding of BaTl(4) are described [C2/m, Z = 4, a = 12.408(3), b = 5.351(1), c = 10.383(2) Å, ? = 116.00(3)°]. Pairs of edge-sharing Tl pentagons are condensed to generate a network of pentagonal biprisms along b that encapsulate Ba atoms. Alternating levels of prisms along c afford six more bifunctional Tl atoms about the waists of the biprisms, giving Ba a coordination number of 16. Each Tl atom is bonded to five to seven other Tl atoms and to three to five Ba atoms. There is also strong evidence that Hg substitutes preferentially in the shared edges of the Tl biprisms in BaHg(0.80)Tl(3.20) to generate more strongly bound Hg(2) dimers. Cations that are too small relative to the dimensions of the surrounding polyanionic network make this BaTl(4) structure (and for SrIn(4) and perhaps EuIn(4) as well) one stable alternative to tetragonal BaAl(4)-type structures in which cations are bound in larger hexagon-faced nets, as for BaIn(4) and SrGa(4). Characteristic condensation and augmentation of cation-centered prismatic units is common among many relatively cation- and electron-poor, polar derivatives of Zintl phases gain stability. At the other extreme, the large family of Frank-Kasper phases in which the elements exhibit larger numbers of bonded neighbors are sometimes referred to as orbitally rich.
Related JoVE Video
Enhanced rat islet function and survival in vitro using a biomimetic self-assembled nanomatrix gel.
Tissue Eng Part A
PUBLISHED: 10-19-2010
Show Abstract
Hide Abstract
Peptide amphiphile (PA) is a peptide-based biomaterial that can self-assemble into a nanostructured gel-like scaffold, mimicking the chemical and biological complexity of natural extracellular matrix. To evaluate the capacity of the PA scaffold to improve islet function and survival in vitro, rat islets were cultured in three different groups--(1) bare group: isolated rat islets cultured in a 12-well nontissue culture-treated plate; (2) insert group: isolated rat islets cultured in modified insert chambers; (3) nanomatrix group: isolated rat islets encapsulated within the PA nanomatrix gel and cultured in modified insert chambers. Over 14 days, both the bare and insert groups showed a marked decrease in insulin secretion, whereas the nanomatrix group maintained glucose-stimulated insulin secretion. Moreover, entire islets in the nanomatrix gel stained positive for dithizone up to 14 days, indicating better maintained glucose-stimulated insulin production. Fluorescein diacetate/propidium iodide staining results also verified necrosis in the bare and insert groups after 7 days, whereas the PA nanomatrix gel maintained islet viability after 14 days. Thus, these results demonstrate the potential of PAs as an intermediary scaffold for increasing the efficacy of pancreatic islet transplantation.
Related JoVE Video
Development of an icosahedral quasicrystal and two approximants in the Ca-Au-Sn system: syntheses and structural analyses.
Inorg Chem
PUBLISHED: 10-12-2010
Show Abstract
Hide Abstract
The realm of Tsai-type (YCd(6)-type) quasicrystals (QCs) and their approximants (ACs) continues to expand to the east in the periodic table. The heavy tetrel Sn is now one of the major components in the new Ca(15.0(5))Au(60.0(4))Sn(25.0(2)) (atom %) icosahedral QC and in the corresponding 1/1 and 2/1 ACs. (The 2/1 AC with Yb is also established.) Single-crystal X-ray diffraction on a 1/1 AC gives the refined formula of Ca(3)Au(14.36(3))Sn(4.38(5)) in space group Im3, a = 15.131(1) Å, whereas a representative 2/1 AC gives Ca(13)Au(47.2(1))Sn(28.1(1)), Pa3 and a = 24.444(1) Å. Both ACs contain five-shell multiply endohedral triacontahedral clusters as the common building blocks, as in the parent structure of YCd(6). The 2/1 AC also contains four Ca(2)-dimer-centered prolate rhombohedra (PRs) in the unit cell. The long-range order between triacontahedra and PRs in the 2/1 AC is the same as those in Bergman-type 2/1 ACs. A TB-LMTO-ASA calculation on an ideal 1/1 AC model reveals a shallow pseudogap in the total densities-of-states data around the Fermi energy, as expected. The depth of the pseudogap is considerably enhanced through interactions between the Ca 3d states and s and p states of Au and Sn.
Related JoVE Video
Contrasts in structural and bonding representations among polar intermetallic compounds. Strongly differentiated Hamilton populations for three related condensed cluster halides of the rare-earth elements.
Inorg Chem
PUBLISHED: 10-05-2010
Show Abstract
Hide Abstract
The crystal and electronic structures of three related R(3)TnX(3) phases (R = rare-earth metal, Tn = transition metal, X = Cl, I) containing extended mixed-metal chains are compared and contrasted: (1) Pr(3)RuI(3) (P2(1)/m), (2) Gd(3)MnI(3) (P2(1)/m), and (3) Pr(3)RuCl(3) (Pnma). The structures all feature double chains built of pairs of condensed R(6)(Tn) octahedral chains encased by halogen atoms. Pr(3)RuI(3) (1) lacks significant Ru-Ru bonding, evidently because of packing restrictions imposed by the large closed-shell size of iodine. However, the vertex Pr2 atoms on the chain exhibit a marked electronic differentiation. These are strongly bound to the central Ru (and to four I), but very little to four neighboring Pr in the cluster according to bond populations, in contrast to Pr2-Pr "bond" distances that are very comparable to those elsewhere. In Gd(3)MnI(3) (2), the smaller metal atoms allow substantial distortions and Mn-Mn bonding. Pr(3)RuCl(3) (3), in contrast to the iodide (1), can be described in terms of a more tightly bound superstructure of (2) in which both substantial Ru-Ru bonding and an increased number of Pr-Cl contacts in very similar mixed-metal chains are favored by the smaller closed-shell contacts of chlorine. Local Spin Density Approximation (LSDA) Linearized Muffin-Tin Orbital (LMTO)-ASA calculations and Crystal Orbital Hamilton Population (COHP) analyses show that the customary structural descriptions in terms of condensed, Tn-stuffed, R-R bonded polyhedral frameworks are poor representations of the bonding in all. Hamilton bond populations (-ICOHP) for the polar mixed-metal R-Tn and the somewhat smaller R-X interactions account for 75-90% of the total populations in each of these phases, together with smaller contributions and variations for R-R and Tn-Tn interactions. The strength of such R-Tn contributions in polar intermetallics was first established or anticipated by Brewer. The rare-earth-metal atoms are significantly oxidized in these compounds.
Related JoVE Video
Homogeneous insulin and C-Peptide sensors for rapid assessment of insulin and C-peptide secretion by the islets.
Diabetes
PUBLISHED: 07-09-2010
Show Abstract
Hide Abstract
Glucose-stimulated islet insulin or C-peptide secretion experiments are a fundamental tool for studying and assessing islet function. The goal of this work was to develop Ab-based fluorescent homogenous sensors that would allow rapid, inexpensive, near-instantaneous determinations of insulin and C-peptide levels in biological samples.
Related JoVE Video
Src family kinases participate in the regulation of encephalomyocarditis virus-induced cyclooxygenase-2 expression by macrophages.
J. Gen. Virol.
PUBLISHED: 05-26-2010
Show Abstract
Hide Abstract
Src family kinases (SFKs) are non-receptor tyrosine kinases that have been implicated as regulators of the inflammatory response. In this study, the role of SFK activation in the inflammatory response of macrophages to encephalomyocarditis virus (EMCV) infection was examined. Virus infection of macrophages stimulates the expression of cyclooxygenase-2 (COX-2), interleukin (IL)-1beta and inducible nitric oxide synthase (iNOS). Inhibition of SFK attenuates EMCV-induced COX-2 expression and prostaglandin E(2) production, iNOS expression and subsequent nitric oxide production, and IL-1beta expression. EMCV-induced COX-2 expression requires the activation of nuclear factor-kappaB and the mitogen-activated protein kinase p38. Consistent with these previous findings, inhibition of SFKs attenuated the phosphorylation of p38 in response to EMCV infection, suggesting that SFKs may act upstream of p38. These findings provide evidence that SFK activation plays an active role in the regulation of inflammatory gene expression by virus-infected macrophages.
Related JoVE Video
Digital models vs plaster models using alginate and alginate substitute materials.
Angle Orthod
PUBLISHED: 05-21-2010
Show Abstract
Hide Abstract
To compare the dimensional stability of four impression materials over time and to compare OraMetrix digital models vs traditional plaster models.
Related JoVE Video
Novel condensation of Au-centered trigonal prisms in rare-earth-metal-rich tellurides: Er7Au2Te2 and Lu7Au2Te2.
Dalton Trans
PUBLISHED: 05-12-2010
Show Abstract
Hide Abstract
A new monoclinic structure occurs for Er(7)Au(2)Te(2) according to X-ray diffraction analysis of single crystals grown at 1200 degrees C: C2/m, Z = 4, a = 17.8310(9) A, b = 3.9819(5) A, c = 16.9089(9) A, beta = 104.361(4) degrees. The isostructural Lu(7)Au(2)Te(2) also exists according to X-ray powder pattern means, a = 17.536(4) A, b = 3.9719(4) A, c = 16.695(2) A, beta = 104.33(1) degrees. The structure contains zigzag chains of condensed, Au-centered tricapped trigonal prisms (TCTP) of Er along c that also share basal faces along b to generate puckered sheets. Further bi-face-capping Er atoms between these generate the three dimensional network along a, with tellurium in cavities outlined by augmented trigonal prismatic Er polyhedra. Bonding analysis via LMTO-DFT methods reveal very significant Er-Au bonding interactions, as quantified by their energy-weighted Hamilton overlap populations (-ICOHP), approximately 49% of the total for all interactions. These and similar Er-Te contributions sharply contrast with the small Er-Er population, only approximately 14% of the total in spite of the high proportion of Er-Er contacts. The strong polar bonding of Er to the electronegative Au and Te leaves Er relatively oxidized, with many of its 5d states falling above the Fermi level and empty. The contradiction with customary representations of structures that highlight rare-earth metal clusters is manifest. The large Er-Au Hamilton overlap population is in accord with the strong bonding between early and late transition metals first noted by Brewer in 1973. The relationship of this structure to the more distorted orthorhombic (Imm2) structure type of neighboring Dy(7)Ir(2)Te(2) is considered.
Related JoVE Video
M3(Au,Ge)19 and M(3.25)(Au,Ge)18 (M = Ca, Yb): distinctive phase separations driven by configurational disorder in cubic YCd6-type derivatives.
Inorg Chem
PUBLISHED: 04-16-2010
Show Abstract
Hide Abstract
Exploratory syntheses in the M-Au-Ge (M = Ca, Yb) systems have led to the discovery of two cleanly separated non-stoichiometric phases M(3)Au(approximately 14.4)Ge(approximately 4.6) (I) and M(3.25)Au(approximately 12.7)Ge(approximately 5.3) (II). Single crystal X-ray studies reveal that both (space group Im3) feature body-centered-cubic packing of five-shell multiply endohedral clusters that resemble those in the parent YCd(6) (= Y(3)Cd(18)) and are akin to approximate phases in other quasicrystal systems. However, differences resulting from various disorders in these are distinctive. The innermost cluster in the M(3)Au(approximately 14.4)Ge(approximately 4.6) phase (I) remains a disordered tetrahedron, as in the YCd(6) parent. In contrast, its counterpart in the electron-richer M(3.25)Au(approximately 12.7)Ge(approximately 5.3) phase (II) is a "rattling" M atom. The structural differentiations between I and II exhibit strong correlations between lattice parameters, cluster sizes, particular site occupancies, and valence electron counts.
Related JoVE Video
Multiple nonstoichiometric phases with discrete composition ranges in the CaAu5-CaAu4Bi-BiAu2 system. A case study of the chemistry of spinodal decomposition.
J. Am. Chem. Soc.
PUBLISHED: 04-03-2010
Show Abstract
Hide Abstract
Synthetic explorations in the CaAu(5)-CaAu(4)Bi-BiAu(2) system at 400 degrees C reveal five separate solid solution regions that show three distinct substitution patterns in the CaAu(5) parent: (I) CaAu(4)(Au(1-m)Bi(m)) with 0 < or = m < or = 0.15(1), (II) 0.33(1) < or = m < or = 0.64(1), (III) 0.85(4) < or = m < or = 0.90(2); (IV) (Ca(1-r)Au(r))Au(4)(Bi(1-s)Au(s)) with 0 < or = r < or = 0.39(1) and 0 < or = s < or = 0.12(2); (V) (Ca(1-p-q)Au(p)Bi(q))Au(4)Bi with 0.09(2) < or = p < or = 0.13(1) and 0.31(2) < or = q < or = 0.72(4). Single crystal X-ray studies establish that all of these phase regions have common cubic symmetry F43m and that their structures (MgCu(4)Sn-type, an ordered derivative of MgCu(2)) all feature three-dimensional networks of Au(4) tetrahedra, in which the truncated tetrahedra are centered and capped by Ca/Au, Au/Bi, or Ca/Au/Bi mixtures to give 16-atom Friauf polyhedra. TB-LMTO-ASA and -COHP calculations also reveal that direct interactions between Ca-Au and Ca-Bi pairs of atoms are relatively weak and that the Bi-Au interactions in the unstable ideal CaAu(4)Bi are antibonding in character at E(F) but that their bonding is optimized at +/-1 e. Compositions between the five nonstoichiometric phases appear to undergo spinodal decompositions. The last phenomenon has been confirmed by HRTEM, STEM-HAADF, EPMA, and XRD studies of the nominal composition CaAu(4.25)Bi(0.75). Its DTA analyses suggest that the phases resulting from spinodal decomposition have nearly the same melting point (approximately 807 degrees C), as expected, and that they are interconvertible through peritectic reactions at approximately 717 degrees C.
Related JoVE Video
K(23)Au(12)Sn(9)--an intermetallic compound containing a large gold-tin cluster: synthesis, structure, and bonding.
Inorg Chem
PUBLISHED: 01-13-2010
Show Abstract
Hide Abstract
A polyanionic unit {Au(12)Sn(9)} with a novel "corrugated sheet" shape occurs in K(23)Au(12)Sn(9). The compound was obtained by fusion of the pure elements in tantalum ampules at high temperatures followed by programmed cooling, and the structure was determined by X-ray diffraction: I42m (No. 121), a = 20.834(3), c = 6.818(1) A, Z = 2. The large heteroatomic cluster has D(2d) point symmetry and features a central four bonded (4b-) Sn, eight 3b- or 2b-Sn on the perimeter, and 24 linking nearly linear Sn-Au bonds at 12 Au atoms. Formula splitting according to the Zintl concept suggests that the compound is one electron deficient, and linear muffin-tin-orbital (LMTO) electronic structure calculations show that the Fermi level (E(F)) lies near a band gap at around 0.5 eV, that is, an incompletely filled valence band in concert with favorable atom packing. Large relative -ICOHP values for Au-Sn are consistent with the observed maximization of the number of heteroatomic bonds, whereas the numerous K-Sn and K-Au contacts contribute approximately 40 % of the total -ICOHP. Extended-Huckel population and molecular orbital analyses indicate that the open band feature originates from 5p states that are associated with the 2b-corner Sn atoms. In accord with the electronic structure calculations, magnetic susceptibility measurements show a nearly temperature-independent paramagnetic property.
Related JoVE Video
Gold tetrahedra as building blocks in K3Au5Tr (Tr = In, Tl) and Rb2Au3Tl and in other compounds: a broad group of electron-poor intermetallic phases.
Inorg Chem
PUBLISHED: 12-17-2009
Show Abstract
Hide Abstract
The alkali-metal gold trielides K(3)Au(5)Tr (Tr = In (I), Tl (II)) and Rb(2)Au(3)Tl (III) have been obtained directly from the elements, and their orthorhombic structures determined by single-crystal X-ray diffraction means (I/II: Imma, a = 5.562(1), 5.595(1); b = 19.645(4),19.706(4); c = 8.502(2), 8.430(2) A; Z = 4, respectively; III: Pmma, a = 5.660(1), b = 6.741(1), c = 9.045(2) A, Z = 4). These exhibit zigzag chains of Tr that link puckered sheets (I/II) or chains (III) of gold tetrahedra condensed through shared vertices. The segregation of Au and Tr components is striking relative to the evidently stronger and preferred Au-Tr bonding in neighboring gold- and alkali-metal-poorer triel phases. The close packing of K/Rb (A) about the gold tetrahedra gives each A and Au(4) component 7-10 and 10 neighbors of the other type, respectively. Tight-binding-linear-muffin-tin-orbital-atomic sphere approximation band structure calculations show that the title phases lie near or at electronic pseudogaps. The gold substructure is the dominant feature of the densities of states, with moderately broad 5d(10) features as favored by relativistic effects. Likewise, crystal orbital Hamilton population results indicate optimization of Au-Au bonding at the expense of the stronger heteroatomic Au-Tr interactions. Stabilization of these unusual structures appears to follow in part from the presence of numerous short and individually weak A-Au interactions, as manifested by appreciable mixing of s, p, and d valence orbitals on A into network bonding states, Au 5d in particular. These and related phases define a family of Au(4)-based phases with particularly low e/a values of 1.2 to approximately 2.3 (over all atoms, omitting Au 5d), closely related to the cubic Laves-type structures. The same region also contains Tr-richer tunnel and network structures with relatively fewer cations that also appear to be dominated by Au-Au and Au-Tr bonding.
Related JoVE Video
AMP-activated protein kinase attenuates nitric oxide-induced beta-cell death.
J. Biol. Chem.
PUBLISHED: 11-20-2009
Show Abstract
Hide Abstract
During the initial autoimmune response in type 1 diabetes, islets are exposed to a damaging mix of pro-inflammatory molecules that stimulate the production of nitric oxide by beta-cells. Nitric oxide causes extensive but reversible cellular damage. In response to nitric oxide, the cell activates pathways for functional recovery and adaptation as well as pathways that direct beta-cell death. The molecular events that dictate cellular fate following nitric oxide-induced damage are currently unknown. In this study, we provide evidence that AMPK plays a primary role controlling the response of beta-cells to nitric oxide-induced damage. AMPK is transiently activated by nitric oxide in insulinoma cells and rat islets following IL-1 treatment or by the exogenous addition of nitric oxide. Active AMPK promotes the functional recovery of beta-cell oxidative metabolism and abrogates the induction of pathways that mediate cell death such as caspase-3 activation following exposure to nitric oxide. Overall, these data show that nitric oxide activates AMPK and that active AMPK suppresses apoptotic signaling allowing the beta-cell to recover from nitric oxide-mediated cellular stress.
Related JoVE Video
Synthesis, structure, and bonding in K12Au21Sn4. A polar intermetallic compound with dense Au20 and open AuSn4 layers.
Inorg Chem
PUBLISHED: 10-31-2009
Show Abstract
Hide Abstract
The new phase K(12)Au(21)Sn(4) has been synthesized by direct reaction of the elements at elevated temperatures. Single crystal X-ray diffraction established its orthorhombic structure, space group Pmmn (No. 59), a = 12.162(2); b = 18.058(4); c = 8.657(2) A, V = 1901.3(7) A(3), and Z = 2. The structure consists of infinite puckered sheets of vertex-sharing gold tetrahedra (Au(20)) that are tied together by thin layers of alternating four-bonded-Sn and -Au atoms (AuSn(4)). Remarkably, the dense but electron-poorer blocks of Au tetrahedra coexist with more open and saturated Au-Sn layers, which are fragments of a zinc blende type structure that maximize tetrahedral heteroatomic bonding outside of the network of gold tetrahedra. LMTO band structure calculations reveal metallic properties and a pseudogap at 256 valence electrons per formula unit, only three electrons fewer than in the title compound and at a point at which strong Au-Sn bonding is optimized. Additionally, the tight coordination of the Au framework atoms by K plays an important bonding role: each Au tetrahedra has 10 K neighbors and each K atom has 8-12 Au contacts. The appreciably different role of the p element Sn in this structure from that in the triel members in K(3)Au(5)In and Rb(2)Au(3)Tl appears to arise from its higher electron count which leads to better p-bonding (valence electron concentrations = 1.32 versus 1.22).
Related JoVE Video
Facilitative glucose transporter 9 expression affects glucose sensing in pancreatic beta-cells.
Endocrinology
PUBLISHED: 10-06-2009
Show Abstract
Hide Abstract
Facilitative glucose transporters (GLUTs) including GLUT9, accelerate the facilitative diffusion of glucose across the plasma membrane. Studies in GLUT2-deficient mice suggested the existence of another GLUT in the mammalian beta-cell responsible for glucose sensing. The objective of this study was to determine the expression and function of GLUT9 in murine and human beta-cells. mRNA and protein expression levels were determined for both isoforms of GLUT9 in murine and human isolated islets as well as insulinoma cell lines (MIN6). Immunohistochemistry and subcellular localization were performed to localize the protein within the cell. Small interfering RNA knockdown of GLUT9 was used to determine the effect of this transporter, in the presence of GLUT2, on cell metabolism and insulin secretion in MIN6 and INS cells. In this report we demonstrate that GLUT9a and GLUT9b are expressed in pancreatic islets and that this expression localizes to insulin-containing beta-cells. Subcellular localization studies indicate that mGLUT9b is found associated with the plasma membrane as well as in the high-density microsome fraction and low-density microsome fraction, whereas mGLUT9a appears to be located only in the high-density microsome and low-density microsome under basal conditions. Functionally GLUT9 appears to participate in the regulation of glucose-stimulated insulin secretion in addition to GLUT2. small interfering RNA knockdown of GLUT9 results in reduced cellular ATP levels that correlate with reductions in glucose-stimulated insulin secretion in MIN6 and INS cells. These studies confirm the expression of GLUT9a and GLUT9b in murine and human beta-cells and suggest that GLUT9 may participate in glucose-sensing in beta-cells.
Related JoVE Video
Nitric oxides mediates a shift from early necrosis to late apoptosis in cytokine-treated ?-cells that is associated with irreversible DNA damage.
Am. J. Physiol. Endocrinol. Metab.
PUBLISHED: 09-08-2009
Show Abstract
Hide Abstract
For many cell types, including pancreatic ?-cells, nitric oxide is a mediator of cell death; however, it is paradoxical that for a given cell type nitric oxide can induce both necrosis and apoptosis. This report tests the hypothesis that cell death mediated by nitric oxide shifts from an early necrotic to a late apoptotic event. Central to this transition is the ability of ?-cells to respond and repair nitric oxide-mediated damage. ?-Cells have the ability to repair DNA that is damaged following 24-h incubation with IL-1; however, cytokine-induced DNA damage becomes irreversible following 36-h incubation. This irreversible DNA damage following 36-h incubation with IL-1 correlates with the activation of caspase-3 (cleavage and activity). The increase in caspase activity correlates with reductions in endogenous nitric oxide production, as nitric oxide is an inhibitor of caspase activity. In contrast, caspase cleavage or activation is not observed under conditions in which ?-cells are capable of repairing damaged DNA (24-h incubation with cytokines). These findings provide evidence that ?-cell death in response to cytokines shifts from an early necrotic process to apoptosis and that this shift is associated with irreversible DNA damage and caspase-3 activation.
Related JoVE Video
Repair of nitric oxide-damaged DNA in beta-cells requires JNK-dependent GADD45alpha expression.
J. Biol. Chem.
PUBLISHED: 08-02-2009
Show Abstract
Hide Abstract
Proinflammatory cytokines induce nitric oxide-dependent DNA damage and ultimately beta-cell death. Not only does nitric oxide cause beta-cell damage, it also activates a functional repair process. In this study, the mechanisms activated by nitric oxide that facilitate the repair of damaged beta-cell DNA are examined. JNK plays a central regulatory role because inhibition of this kinase attenuates the repair of nitric oxide-induced DNA damage. p53 is a logical target of JNK-dependent DNA repair; however, nitric oxide does not stimulate p53 activation or accumulation in beta-cells. Further, knockdown of basal p53 levels does not affect DNA repair. In contrast, expression of growth arrest and DNA damage (GADD) 45alpha, a DNA repair gene that can be regulated by p53-dependent and p53-independent pathways, is stimulated by nitric oxide in a JNK-dependent manner, and knockdown of GADD45alpha expression attenuates the repair of nitric oxide-induced beta-cell DNA damage. These findings show that beta-cells have the ability to repair nitric oxide-damaged DNA and that JNK and GADD45alpha mediate the p53-independent repair of this DNA damage.
Related JoVE Video
Phosphatidylinositol 3-kinase regulates macrophage responses to double-stranded RNA and encephalomyocarditis virus.
J Innate Immun
PUBLISHED: 06-24-2009
Show Abstract
Hide Abstract
Virus infection of macrophages stimulates the expression of proinflammatory and antiviral genes interleukin-1 (IL-1), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). In this study, we show that phosphatidylinositol 3-kinase (PI3K) is required for the inflammatory response of macrophages to virus infection. When macrophages are infected with encephalomyocarditis virus (EMCV) there is a rapid and transient activation of PI3K and phosphorylation of its downstream target Akt. Inhibitors of PI3K attenuate EMCV- and double-stranded RNA-induced iNOS, COX-2 and IL-1 beta expression in RAW264.7 cells and mouse peritoneal macrophages. The attenuation of inflammatory gene expression in response to PI3K inhibition correlates with the induction of macrophage apoptosis. The morphology of macrophages shifts from activation in response to EMCV infection to apoptosis in the cells treated with PI3K inhibitors and EMCV. These morphological changes are accompanied by the activation of caspase-3. These findings suggest that PI3K plays a central role in the regulation of macrophage responses to EMCV infection. When PI3K is activated, it participates in the regulation of inflammatory gene expression; however, if PI3K is inhibited macrophages are unable to mount an inflammatory antiviral response and die by apoptosis.
Related JoVE Video
The antimony-based type I clathrate compounds Cs(8)Cd(18)Sb(28) and Cs(8)Zn(18)Sb(28).
Angew. Chem. Int. Ed. Engl.
PUBLISHED: 06-19-2009
Show Abstract
Hide Abstract
In phase: The title compounds lie in a new region of phase space for such a structure, and have stoichiometries in accord with a classical Zintl phase formulation. The small semiconductor gaps indicated by DFT calculations are also supported by their diamagnetic susceptibilities.
Related JoVE Video
Centric and non-centric Ca3Au(approximately 7.5)Ge(approximately 3.5): electron-poor derivatives of La3Al11. Syntheses, structures, and bonding analyses.
Inorg Chem
PUBLISHED: 06-09-2009
Show Abstract
Hide Abstract
Two La(3)Al(11) type derivatives have been discovered in the Ca-Au-Ge system and structurally characterized by single-crystal X-ray diffraction. Compositions Ca(3)Au(7.16(6))Ge(3.84(6)) (1) and Ca(3)Au(7.43(9))Ge(3.57(9)) (2) lie within a non-centric Imm2 phase region with a approximately 4.40 A, b approximately 13.06 A, c approximately 9.60 A. The Au-richer and electron-poorer Ca(3)Au(7.50(1))Ge(3.50(1)) (3) and Ca(3)Au(8.01(1))Ge(2.99(1)) (4) occur within a centric Pnnm phase region with a approximately 9.50 A, b approximately 13.20 A, c approximately 4.43 A. Both phases contain complex [Au,Ge](11)(6-) polyanionic networks made up of hexagonal and pentagonal prisms that are filled with the electropositive Ca atoms. Both 3:11 phases represent opposed 1 x 3 x 1 superstructure distortions of CaAu(2)Ge(2) (ThCr(2)Si(2) type, I4/mmm), the structure of which has also been re-determined in this work. Linear muffin-tin-orbital (LMTO) calculations reveal that the symmetry variations induced by changes of the Au contents in the present 3:11 phases are consequences of bonding and structural optimizations. The hypothetical "CaAu(2.33-2.67)Ge(1.33-1.00)cube(0.33)" compositions, which are close to those of 1-4, follow through creation and elimination of vacancies within the electronegative networks of CaAu(2)Ge(2).
Related JoVE Video
BaHg2Tl2. An unusual polar intermetallic phase with strong differentiation between the neighboring elements mercury and thallium.
J. Am. Chem. Soc.
PUBLISHED: 05-23-2009
Show Abstract
Hide Abstract
High yields of the novel BaHg(2)Tl(2) are achieved from reactions of the appropriate cast alloys at approximately 400 degrees C. (Isotypic SrHg(2)Tl(2) also exists.) The tetragonal barium structure (P4(2)/mnm, a = 10.606 A, c = 5.159 A) was refined from both single-crystal X-ray and neutron powder diffraction data in order to ensure the atom site assignments although distances and calculated atom site population also support the results. The Hg and Tl network atoms are distinctive in their functions and bonding. Parallel chains of Hg hexagons and of Tl tetrahedra along c are constructed from polyhedra that share opposed like edges, and these are in turn interconnected by Hg-Tl bonds. Overall, the number of Tl-Tl bonds per cell exceeds the Hg-Hg type by 20:12, but these are approximately 1:2 each in bonding according to their average -ICOHP values (related to overlap populations). Barium is bound within a close 15-atom polyhedron, 12 atoms of which are the more electronegative Hg. LMTO-ASA calculations show that scalar relativistic effects are particularly important for Hg 5d-6s mixing in Hg-Hg and Hg-Tl bonding, whereas relatively separate Tl 6s and 6p states are more important in Tl-Tl interactions. The 6p states of Hg and Tl and 5d of Ba define a dominant conduction band around E(F), and the phase is metallic and Pauli-like paramagnetic. The thallium characteristics here are close to those in numerous alkali-metal-Tl cluster systems. Other active metal-mercury phases that have been studied theoretically are all distinctly electron-richer and more reduced, and without appreciable net 5d, 6s contributions to Hg-Hg bonding.
Related JoVE Video
Glucose-modulated tyrosine nitration in beta cells: targets and consequences.
Arch. Biochem. Biophys.
PUBLISHED: 04-30-2009
Show Abstract
Hide Abstract
Hyperglycemia, key factor of the pre-diabetic and diabetic pathology, is associated with cellular oxidative stress that promotes oxidative protein modifications. We report that protein nitration is responsive to changes in glucose concentrations in islets of Langerhans and insulinoma beta cells. Alterations in the extent of tyrosine nitration as well as the cellular nitroproteome profile correlated tightly with changing glucose concentrations. The target proteins we identified function in protein folding, energy metabolism, antioxidant capacity, and membrane permeability. Nitration of heat shock protein 60 in vitro was found to decrease its ATP hydrolysis and interaction with proinsulin, suggesting a mechanism by which protein nitration could diminish insulin secretion. This was supported by our finding of a decrease in stimulated insulin secretion following glycolytic stress in cultured cells. Our results reveal that protein tyrosine nitration may be a previously unrecognized factor in beta-cell dysfunction and the pathogenesis of diabetes.
Related JoVE Video
R(5)Pn(3)-type phases of the heavier trivalent rare-earth-metal pnictides (Pn = Sb, Bi): new phase transitions for Er(5)Sb(3) and Tm(5)Sb(3).
Inorg Chem
PUBLISHED: 04-04-2009
Show Abstract
Hide Abstract
The syntheses and distributions of binary R(5)Pn(3) phases among the hexagonal Mn(5)Si(3) (M), and the very similar orthorhombic beta-Yb(5)Sb(3) (Y) and Y(5)Bi(3) (YB) structure types have been studied for R = Y, Gd-Lu and Pn = Sb, Bi. Literature reports of M and YB-type structure distributions among R(5)Pn(3) phases, R = Y, Gd-Ho, are generally confirmed. The reported M-type Er(5)Sb(3) could not be reproduced. Alternate stabilization of Y-type structures by interstitials H or F has been disproved for these nominally trivalent metal pnictides. Single crystal structures are reported for (a) the low temperature YB form of Er(5)Sb(3) (Pnma, a = 7.9646(9) A, b = 9.176(1) A, c = 11.662(1) A), (b) the YB- and high temperature Y-types of Tm(5)Sb(3) (both Pnma, a = 7.9262(5), 11.6034(5) A, b = 9.1375(6), 9.1077(4) A, c = 11.6013(7), 7.9841(4) A, respectively), and (c) the YB structure of Lu(5)Sb(3), a = 7.8847(4) A, b = 9.0770(5) A, c = 11.5055(6) A. Reversible, temperature-driven phase transitions (beta-Yb(5)Sb(3) left arrow over right arrow Y(5)Bi(3) types) for the former Er(5)Sb(3) and Tm(5)Sb(3) around 1100 degrees C and the means of quenching the high temperature Y form, have been esstablished. According to their magnetic susceptibilities, YB-types of Er(5)Sb(3) and Tm(5)Sb(3) contain trivalent cations. Tight-binding linear muffin-tin-orbital method within the atomic sphere approximation (TB-LMTO-ASA) calculations for the two structures of Tm(5)Sb(3) reveal generally similar electronic structures but with subtle Tm-Tm differences supporting their relative stabilities. The ambient temperature YB-Tm(5)Sb(3) shows a deep pseudogap at E(F), approaching that of a closed shell electronic state. Short R-R bonds (3.25-3.29 A) contribute markedly to the structural stabilities of both types. The Y-type structure of Tm(5)Sb(3) shows both close structural parallels to, and bonding contrasts with, the nominally isotypic, stuffed Ca(5)Bi(3)D and its analogues. Some contradictions in the literature are discussed.
Related JoVE Video
The CDK domain of p21 is a suppressor of IL-1beta-mediated inflammation in activated macrophages.
Eur. J. Immunol.
PUBLISHED: 02-04-2009
Show Abstract
Hide Abstract
Significant morbidity and mortality can be attributed to inflammatory diseases; therefore, a greater understanding of the mechanisms involved in the progression of inflammation is crucial. Here, we demonstrate that p21((WAF1/CIP1)), an established suppressor of cell cycle progression, is a inhibitor of IL-1beta synthesis in macrophages. Mice deficient in p21 (p21(-/-)) display increased susceptibility to endotoxic shock, which is associated with increased serum levels of IL-1beta. Administration of IL-1 receptor antagonist reduces LPS-induced lethality in p21(-/-) mice. Analysis of isolated macrophages, which are one of the central producers of IL-1beta, reveals that deficiency for p21 led to more IL-1beta mRNA and pro-protein synthesis following TLR ligation. The increase in IL-1beta pro-protein is associated with elevated secretion of active IL-1beta by p21(-/-) macrophages. siRNA-mediated knockdown of p21 in human macrophages results in increased IL-1beta secretion as well. A peptide mapping strategy shows that the cyclin-dependent-kinase (CDK)-binding domain of p21 is sufficient to reduce the secretion of IL-1beta by p21(-/-) macrophages. These data suggest a novel role for p21 and specifically for the CDK-binding domain of p21((WAF1/CIP1)) in inhibiting inflammation.
Related JoVE Video
Selective mtDNA mutation accumulation results in beta-cell apoptosis and diabetes development.
Am. J. Physiol. Endocrinol. Metab.
PUBLISHED: 01-21-2009
Show Abstract
Hide Abstract
To test the hypothesis that somatic mitochondrial (mt)DNA mutation accumulation predisposes mice to beta-cell loss and diabetes development, transgenic mice expressing a proofreading-deficient mtDNA polymerase-gamma under the control of the rat insulin-1 promoter were generated. At 6 wk of age, mtDNA mutations reached 0.01% (1.05 mutations/10,000 bp) in islets isolated from transgenic mice. This mutational burden is associated with impaired glucose tolerance and a diabetes prevalence of 52% in male transgenic mice. Female transgenic mice maintain slightly elevated fasting glucose levels, mild glucose intolerance, and a diabetes prevalence of 14%. Diabetes in transgenic animals is associated with insulin insufficiency that results from a significant reduction in beta-cell mass. Importantly, apoptosis of beta-cells is increased 7-fold in female and 11-fold in male transgenic mice compared with littermate controls. These results are consistent with a causative role of somatic mtDNA mutation accumulation in the loss of beta-cell mass and diabetes development.
Related JoVE Video
Surface preparation strategies for improved parallelization and reproducible MALDI-TOF MS ligand binding assays.
ACS Appl Mater Interfaces
Show Abstract
Hide Abstract
Immunoassays are employed in academia and the healthcare and biotech industries for high-throughput, quantitative screens of biomolecules. We have developed monolayer-based immunoassays for MALDI-TOF MS. To improve parallelization, we adapted the workflow to photolithography-generated arrays. Our work shows Parylene-C coatings provide excellent "solvent pinning" for reagents and biofluids, enabling sensitive MS detection of immobilized components. With a unique MALDI-matrix crystallization technique we show routine interassay RSD <10% at picomolar concentrations and highlight platform compatibility for relative and label-free quantitation applications. Parylene-arrays provide high sample densities and promise screening throughputs exceeding 1000 samples/h with modern liquid-handlers and MALDI-TOF systems.
Related JoVE Video
MS-based ligand binding assays with speed, sensitivity, and specificity.
Proteomics
Show Abstract
Hide Abstract
Immunoassays are widely used in biochemical/clinical laboratories owing to their simplicity, speed, and sensitivity. We combined self-assembled monolayer-based immunoassays with MALDI-TOF MS to show that high-fidelity surface preparations with a novel matrix deposition/crystallization technique permits quantitative analysis of monolayer-bound antigens at picomolar detection limits. Calibration curves for intact proteins are possible over a broad concentration range and improved specificity of MS-immunoassays is highlighted by simultaneous label-free quantitation of ligand-bound protein complexes.
Related JoVE Video
Two homologous intermetallic phases in the Na-Au-Zn system with sodium bound in unusual paired sites within 1D tunnels.
Inorg Chem
Show Abstract
Hide Abstract
The Na-Au-Zn system contains the two intermetallic phases Na(0.97(4))Au(2)Zn(4) (I) and Na(0.72(4))Au(2)Zn(2) (II) that are commensurately and incommensurately modulated derivatives of K(0.37)Cd(2), respectively. Compound I crystallizes in tetragonal space group P4/mbm (No. 127), a = 7.986(1) Å, c = 7.971(1) Å, Z = 4, as a 1 × 1 × 3 superstructure derivative of K(0.37)Cd(2) (I4/mcm). Compound II is a weakly incommensurate derivative of K(0.37)Cd(2) with a modulation vector q = 0.189(1) along c. Its structure was solved in superspace group P4/mbm(00g)00ss, a = 7.8799(6) Å, c = 2.7326(4) Å, Z = 2, as well as its average structure in P4/mbm with the same lattice parameters.. The Au-Zn networks in both consist of layers of gold or zinc squares that are condensed antiprismatically along c ([Au(4/2)Zn(4)Zn(4)Au(4/2)] for I and [Au(4/2)Zn(4)Au(4/2)] for II) to define fairly uniform tunnels. The long-range cation dispositions in the tunnels are all clearly and rationally defined by electron density (Fourier) mapping. These show only close, somewhat diffuse, pairs of opposed, ?50% occupied Na sites that are centered on (I) (shown) or between (II) the gold squares. Tight-binding electronic structure calculations via linear muffin-tin-orbital (LMTO) methods, assuming random occupancy of ? ?100% of nonpaired Na sites, again show that the major Hamilton bonding populations in both compounds arise from the polar heteroatomic Au-Zn interactions. Clear Na-Au (and lesser Na-Zn) bonding is also evident in the COHP functions. These two compounds are the only stable ternary phases in the (Cs,Rb,K,Na)-Au-Zn systems, emphasizing the special bonding and packing requirements in these sodium structures.
Related JoVE Video
Ketamine induces toxicity in human neurons differentiated from embryonic stem cells via mitochondrial apoptosis pathway.
Curr Drug Saf
Show Abstract
Hide Abstract
Ketamine is widely used for anesthesia in pediatric patients. Growing evidence indicates that ketamine causes neurotoxicity in a variety of developing animal models. Our understanding of anesthesia neurotoxicity in humans is currently limited by difficulties in obtaining neurons and performing developmental toxicity studies in fetal and pediatric populations. It may be possible to overcome these challenges by obtaining neurons from human embryonic stem cells (hESCs) in vitro. hESCs are able to replicate indefinitely and differentiate into every cell type. In this study, we investigated the toxic effect of ketamine on neurons differentiated from hESCs. Two-week-old neurons were treated with different doses and durations of ketamine with or without the reactive oxygen species (ROS) scavenger, Trolox. Cell viability, ultrastructure, mitochondrial membrane potential (??m), cytochrome c distribution within cells, apoptosis, and ROS production were evaluated. Here we show that ketamine induced ultrastructural abnormalities and dose- and time-dependently caused cell death. In addition, ketamine decreased ??m and increased cytochrome c release from mitochondria. Ketamine also increased ROS production and induced differential expression of oxidative stress-related genes. Specifically, abnormal ultrastructural and ??m changes occurred earlier than cell death in the ketamine-induced toxicity process. Furthermore, Trolox significantly decreased ROS generation and attenuated cell death caused by ketamine in a dose-dependent manner. In conclusion, this study illustrates that ketamine time- and dose-dependently induces human neurotoxicity at supraclinical concentrations via ROS-mediated mitochondrial apoptosis pathway and that these side effects can be prevented by the antioxidant agent Trolox. Thus, hESC-derived neurons might provide a promising tool for studying anesthetic-induced developmental neurotoxicity and prevention strategies.
Related JoVE Video
Conventional and stuffed Bergman-type phases in the Na-Au-T (T = Ga, Ge, Sn) systems: syntheses, structures, coloring of cluster centers, and Fermi sphere-brillouin zone interactions.
Inorg Chem
Show Abstract
Hide Abstract
Bergman-type phases in the Na-Au-T (T = Ga, Ge, and Sn) systems were synthesized by solid-state means and structurally characterized by single-crystal X-ray diffraction studies. Two structurally related (1/1) Bergman phases were found in the Na-Au-Ga system: (a) a conventional Bergman-type (CB) structure, Na(26)Au(x)Ga(54-x), which features empty innermost icosahedra, as refined with x = 18.1 (3), Im3, a = 14.512(2) Å, and Z = 2; (b) a stuffed Bergman-type (SB) structure, Na(26)Au(y)Ga(55-y), which contains Ga-centered innermost icosahedra, as refined with y = 36.0 (1), Im3, a = 14.597(2) Å, and Z = 2. Although these two subtypes have considerable phase widths along with respective tie lines at Na ? 32.5 and 32.1 atom %, they do not merge into a continuous solid solution. Rather, a quasicrystalline phase close to the Au-poor CB phase and an orthorhombic derivative near the Au-rich SB phase lie between them. In contrast, only Au-rich SB phases exist in the Ge and Sn systems, in which the innermost icosahedra are centered by Au rather than Ge or Sn. These were refined for Na(26)Au(40.93(5))Ge(14.07(5)) (Im3, a = 14.581(2) Å, and Z = 2) and Na(26)Au(39.83(6))Sn(15.17(6)) (Im3, a = 15.009(2) Å, and Z = 2), respectively. Occupations of the centers of Bergman clusters are rare. Such centering and coloring correlate with the sizes of the neighboring icosahedra, the size ratios between electropositive and electronegative components, and the values of the average valence electron count per atom (e/a). Theoretical calculations revealed that all of these phases are Hume-Rothery phases, with evident pseudogaps in the density of states curves that arise from the interactions between Fermi surface and Brillouin zone boundaries corresponding to a strong diffraction intensity.
Related JoVE Video
Thin-layer matrix sublimation with vapor-sorption induced co-crystallization for sensitive and reproducible SAMDI-TOF MS analysis of protein biosensors.
J. Am. Soc. Mass Spectrom.
Show Abstract
Hide Abstract
Coupling immunoassays on self-assembled monolayers (SAMs) to matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) provides improved assay selectivity compared with traditional photometric detection techniques. We show that thin-layer-transfer (TLT) of ?-cyano-4-hydroxycinnaminic acid (CHCA) MALDI matrix via vacuum sublimation followed by organic solvent-based vapor-sorption induced co-crystallization (VIC) results in unique matrix/analyte co-crystallization tendencies that optimizes assay reproducibility and sensitivity. Unique matrix crystal morphologies resulted from VIC solvent vapors, indicating nucleation and crystal growth characteristics depend upon VIC parameters. We observed that CHCA microcrystals generated by methanol VIC resulted in >10× better sensitivity, increased analyte charging, and improved precision compared with dried droplet measurements. The uniformity of matrix/analyte co-crystallization across planar immunoassays directed at intact proteins yielded low spectral variation for single shot replicates (18.5 % relative standard deviation, RSD) and signal averaged spectra (<10 % RSD). We envision that TLT and VIC for MALDI-TOF will enable high-throughput, reproducible array-based immunoassays for protein molecular diagnostic assays in diverse biochemical and clinical applications.
Related JoVE Video
Three alkali-metal-gold-gallium systems. Ternary tunnel structures and some problems with poorly ordered cations.
Inorg Chem
Show Abstract
Hide Abstract
Six new intermetallic compounds have been characterized in the alkali metal (A = Na, Rb, Cs)-gold-gallium systems. Three isostructural compounds with the general composition A(0.55)Au(2)Ga(2), two others of AAu(3)Ga(2) (A = Rb, Cs), and the related Na(13)Au(41.2)Ga(30.3) were synthesized via typical high-temperature reactions and their crystal structures determined by single-crystal X-ray diffraction analysis: Na(0.56(9))Au(2)Ga(2) (I, I4/mcm, a = 8.718(1) Å, c = 4.857(1) Å, Z = 4), Rb(0.56(1))Au(2)Ga(2) (II, I4/mcm, a = 8.950(1) Å, c = 4.829(1) Å, Z = 4), Cs(0.54(2))Au(2)Ga(2) (III, I4/mcm, a = 9.077(1) Å, c = 4.815(1) Å, Z = 4), RbAu(3)Ga(2) (IV, Pnma, a = 13.384(3) Å, b = 5.577(1) Å, c = 7.017(1) Å, Z = 4), CsAu(3)Ga(2) (V, Pnma, a = 13.511(3) Å, b = 5.614(2) Å, c = 7.146(1) Å, Z = 4), Na(13)Au(41.2(1))Ga(30.3(1)) (VI, P6 mmm, a = 19.550(3) Å, c = 8.990(2) Å, Z = 2). The first three compounds (I-III) are isostructural with tetragonal K(0.55)Au(2)Ga(2) and likewise contain planar eight-member Au/Ga rings that stack along c to generate tunnels and that contain varying degrees of disordered Na-Cs cations. The cation dispositions are much more clearly and reasonably defined by electron density mapping than through least-squares refinements with conventional anisotropic ellipsoids. Orthorhombic AAu(3)Ga(2) (IV, V) are ordered ternary Rb and Cs derivatives of the SrZn(5) type structure, demonstrating structural variability within the AAu(3)Ga(2) family. All attempts to prepare an isotypic "NaAu(3)Ga(2)" were not successful, but yielded only a similar composition Na(13)Au(41.2)Ga(30.3) (NaAu(3.17)Ga(2.33)) (VI) in a very different structure with two types of cation sites. Crystal orbital Hamilton population (COHP) analysis obtained from tight-binding electronic structure calculations for idealized I-IV via linear muffin-tin-orbital (LMTO) methods emphasized the major contributions of heteroatomic Au-Ga bonding to the structural stability of these compounds. The relative minima (pseudogaps) in the DOS curves for IV correspond well with the valence electron counts of known representatives of this structure type and, thereby, reveal some magic numbers to guide the search for new isotypic compounds. Theoretical calculation of total energies vs volumes obtained by VASP (Vienna Ab initio Simulation Package) calculations for KAu(3)Ga(2) and RbAu(3)Ga(2) suggest a possible transformation from SrZn(5)- to BaZn(5)-types at high pressure.
Related JoVE Video

What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

How does it work?

We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.

Video X seems to be unrelated to Abstract Y...

In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.