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Find video protocols related to scientific articles indexed in Pubmed.
Damage modeling and statistical analysis of optics damage performance in MJ-class laser systems.
Opt Express
PUBLISHED: 11-18-2014
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Modeling the lifetime of a fused silica optic is described for a multiple beam, MJ-class laser system. This entails combining optic processing data along with laser shot data to account for complete history of optic processing and shot exposure. Integrating with online inspection data allows for the construction of a performance metric to describe how an optic performs with respect to the model. This methodology helps to validate the damage model as well as allows strategic planning and identifying potential hidden parameters that are affecting the optic's performance.
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Step-by-Step Fracture of Two-Layer Stacked Graphene Membranes.
ACS Nano
PUBLISHED: 09-29-2014
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Layer-by-layer assembly of graphene has been proven to be an effective way to improve its mechanical properties, but its fracture mechanism, which is crucial for practical device applications, is still not clear and has not been fully studied yet. By consecutive stacking of two graphene monolayers, we fabricate two-layer stacked graphene membranes with a clean interface between the two layers. Fracture behavior of the two-layer stacked graphene membranes is studied using nanoindentation performed by atomic force microscopy. It is found that the fracture force distribution of stacked graphene is very different from that of monolayer graphene. Weibull statistics of fracture forces show that after layer-by-layer stacking of graphene, the membrane becomes less sensitive to the defects during nanoindentation, improving the overall performance of the graphene membranes. Interestingly, a third of our tested membranes show a stepwise fracture, which could serve as a warning message for the mechanical failure of multilayer graphene devices. Our study provides insight into the fracture mechanism of multilayer graphene membranes.
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[Uncertainty analysis of ecological risk assessment caused by heavy-metals deposition from MSWI emission].
Huan Jing Ke Xue
PUBLISHED: 08-28-2014
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The CALPUFF model was applied to simulate the ground-level atmospheric concentrations of Pb and Cd from municipal solid waste incineration (MSWI) plants, and the soil concentration model was used to estimate soil concentration increments after atmospheric deposition based on Monte Carlo simulation, then ecological risk assessment was conducted by the potential ecological risk index method. The results showed that the largest atmospheric concentrations of Pb and Cd were 5.59 x 109-3) microg x m(-3) and 5.57 x 10(-4) microg x m(-3), respectively, while the maxima of soil concentration incremental medium of Pb and Cd were 2.26 mg x kg(-1) and 0.21 mg x kg(-1), respectively; High risk areas were located next to the incinerators, Cd contributed the most to the ecological risk, and Pb was basically free of pollution risk; Higher ecological hazard level was predicted at the most polluted point in urban areas with a 55.30% probability, while in rural areas, the most polluted point was assessed to moderate ecological hazard level with a 72.92% probability. In addition, sensitivity analysis of calculation parameters in the soil concentration model was conducted, which showed the simulated results of urban and rural area were most sensitive to soil mix depth and dry deposition rate, respectively.
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A new pregnane glycoside from Rubus phoenicolasius and its antiproliferative activity.
Nat. Prod. Res.
PUBLISHED: 08-26-2014
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Chemical investigations of the whole plant ethanol extract of Rubus phoenicolasius led to the isolation and identification of a new pregnane glycoside, 3-O-?-glucopyranosyl-3?,15?-dihydroxypregn-5-en-20-one (1), along with other nine known compounds (2-10). All the isolates were reported from this plant for the first time. The structure of compound 1 was determined by detailed analysis of its spectral data including 1D and 2D NMR. In vitro anti-proliferative activities of compounds 1-3 on MCF-7 and NCI-H460 tumour cell lines were evaluated, and compound 1 was active against the two cell lines with IC50 values of 15.6 and 13.5 ?M, respectively.
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Vertically Architectured Stack of Multiple Graphene Field-Effect Transistors for Flexible Electronics.
Small
PUBLISHED: 08-13-2014
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Vertically architectured stack of multiple graphene field-effect transistors (GFETs) on a flexible substrate show great mechanical flexibility and robustness. The four GFETs are integrated in the vertical direction, and dually gated GFETs with graphene channel, PMMA dielectrics, and graphene gate electrodes are realized.
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Re-sensitization of 5-FU resistance by SPARC through negative regulation of glucose metabolism in hepatocellular carcinoma.
Tumour Biol.
PUBLISHED: 08-12-2014
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Secreted protein, acidic and rich in cysteine (SPARC), a calcium-binding matricellular glycoprotein, is implicated in the progression of many cancers. Currently, there is growing evidence for important functions of SPARC in a variety of cancers and its role in cancer depends on tumor types. In this study, we reported SPARC negatively regulated glucose metabolism in hepatocellular carcinoma (HCC). Overexpression of SPARC inhibited glucose uptake and lactate product through downregulation of key enzymes of glucose metabolism. On the other hand, knock down of SPARC reversed the phenotypes. Meanwhile, exogenous expression of SPARC in HepG2 cells resulted in tolerance to low glucose and was correlated with AMPK pathway. Interestingly, the 5-fluorouracil (5-FU)-resistant HepG2 cells showed increased glucose metabolism and downregulated SPARC levels. Finally, we reported the overexpression of SPARC re-sensitize 5-FU-resistant cells to 5-FU through inhibition of glycolysis both in vitro and in vivo. Our study proposed a novel function of SPARC in the regulation of glucose metabolism in hepatocellular carcinoma and will facilitate the development of therapeutic strategies for the treatments of liver tumor patients.
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Topological surface state enhanced photothermoelectric effect in Bi2Se3 nanoribbons.
Nano Lett.
PUBLISHED: 07-23-2014
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The photothermoelectric effect in topological insulator Bi2Se3 nanoribbons is studied. The topological surface states are excited to be spin-polarized by circularly polarized light. Because the direction of the electron spin is locked to its momentum for the spin-helical surface states, the photothermoelectric effect is significantly enhanced as the oriented motions of the polarized spins are accelerated by the temperature gradient. The results are explained based on the microscopic mechanisms of a photon induced spin transition from the surface Dirac cone to the bulk conduction band. The as-reported enhanced photothermoelectric effect is expected to have potential applications in a spin-polarized power source.
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Integrating novel chemical weapons and evolutionarily increased competitive ability in success of a tropical invader.
New Phytol.
PUBLISHED: 07-08-2014
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The evolution of increased competitive ability (EICA) hypothesis and the novel weapons hypothesis (NWH) are two non-mutually exclusive mechanisms for exotic plant invasions, but few studies have simultaneously tested these hypotheses. Here we aimed to integrate them in the context of Chromolaena odorata invasion. We conducted two common garden experiments in order to test the EICA hypothesis, and two laboratory experiments in order to test the NWH. In common conditions, C. odorata plants from the nonnative range were better competitors but not larger than plants from the native range, either with or without the experimental manipulation of consumers. Chromolaena odorata plants from the nonnative range were more poorly defended against aboveground herbivores but better defended against soil-borne enemies. Chromolaena odorata plants from the nonnative range produced more odoratin (Eupatorium) (a unique compound of C. odorata with both allelopathic and defensive activities) and elicited stronger allelopathic effects on species native to China, the nonnative range of the invader, than on natives of Mexico, the native range of the invader. Our results suggest that invasive plants may evolve increased competitive ability after being introduced by increasing the production of novel allelochemicals, potentially in response to naïve competitors and new enemy regimes.
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Two new 2,3-seco-hopane triterpene derivatives from Megacodon stylophorus and their antiproliferative and antimicrobial activities.
Planta Med.
PUBLISHED: 07-04-2014
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Chemical investigation of the ethanol extract of the whole plant of Megacodon stylophorus led to the isolation and identification of two new seco-hopane triterpenoids, 2,3-seco-22(29)-hopene-2-carboxyl-3-aldehyde (1) and 2,3-seco-4(23),22(29)-hopene-2-carboxyl-3-aldehyde (2), along with 10 known compounds, 3-12. All the isolates were reported from this plant for the first time. The structures of compounds 1 and 2 were determined by detailed analysis of their spectral data including 1D and 2D?NMR. In addition, compound 1 was further analyzed by X-ray crystallography. Compounds 1-3 were evaluated for their in vitro anti-proliferative activities on HeLa, MCF-7, and Hep-G2 tumor cell lines. Compound 2 was active against the three cell lines with IC50 values of 3.6, 7.5, and 13.6 µM, respectively, while compound 1 exhibited cytotoxicity on MCF-7 (IC50 14.0 µM) and HeLa (IC50 18.2 µM) cell lines. Antimicrobial activities of compounds 1-2 (minimum inhibitory concentration values in the range of 3.12-12.50 mg/mL) were also observed.
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Characterization of a novel antimicrobial peptide with chiting-biding domain from Mytilus coruscus.
Fish Shellfish Immunol.
PUBLISHED: 06-27-2014
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Using reverse phase high performance liquid chromatography (RP-HPLC), a novel antimicrobial peptide with 55 amino acid residues was isolated from the hemolymph of Mytilus coruscus. This new antimicrobial peptide displays predominant antimicrobial activity against fungi and Gram-positive bacteria. The molecular mass and the N-terminal sequence of this peptide were analyzed by Mass Spectrometry and Edman degradation, respectively. This antimicrobial peptide, with molecular mass of 6621.55 Da, is characterized by a chitin-biding domain and by 6 Cysteine residues engaged in three intra-molecular disulfide bridges. The full-length of cDNA sequence of this new peptide was obtained by rapid amplification of cDNA ends (RACE) and the encoded precursor was turn out to be a chitotriosidase-like protein. Therefore, we named the precursor with mytichitin-1 and the new antimicrobial peptide (designated as mytichitin-CB) is the carboxyl-terminal part of mytichitin-1. The mRNA transcripts of mytichitin-1 are mainly detected in gonad and the expression level of mytichitin-1 in gonad was up-regulated and reached the highest level at 12 h after bacterial challenge, which was 9-fold increase compared to that of the control group. These results indicated that mytichitin-1 was involved in the host immune response against bacterial infection and might contribute to the clearance of invading bacteria.
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A trehalose ester from Lancea tibetica.
Nat. Prod. Res.
PUBLISHED: 06-26-2014
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A phytochemical study of the 95% ethanolic extract of the whole plant of Lancea tibetica Hook. f. et Thoms. led to the isolation of a new trehalose ester, 6-O-undecanoyl-?,?-trehalose (1), along with 23 known compounds (2-24), of which compounds 2-17 were isolated from this plant for the first time. The structures of these compounds were established on the basis of spectroscopic methods. Compound 1 was evaluated for their in vitro anti-proliferative activities against MCF-7, NCI-H460 and Hep-G2 tumour cell lines. Compound 1 exhibited potent inhibitory activity against NCI-H460 cell growth, in contrast to moderate cytotoxic activity against MCF-7 and Hep-G2 cells.
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Magnetic moments in graphene with vacancies.
Nanoscale
PUBLISHED: 06-24-2014
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Vacancies can induce local magnetic moments in graphene, paving the way to make magnetic functional graphene. Due to the interaction between magnetic moments and conduction carriers, the magnetotransport properties of graphene can be modulated. Here, the effects of vacancy induced magnetic moments on the electrical properties of graphene are studied via magnetotransport measurements and spin-polarized density functional theory calculations. We show by quantum Hall measurements that a sharp resonant V? state is introduced in the midgap region of graphene with vacancies, resulting in the local magnetic moment. The coupling between the localized V? state and the itinerant carrier is tuned by varying the carrier concentration, temperature, magnetic field, and vacancy density, which results in a transition between hopping transport and the Kondo effect and a transition between giant negative magnetoresistance (MR) and positive MR. This modulated magnetotransport is valuable for graphene based spintronic devices.
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8-60hIPP5(m)-induced G2/M cell cycle arrest involves activation of ATM/p53/p21(cip1/waf1) pathways and delayed cyclin B1 nuclear translocation.
Asian Pac. J. Cancer Prev.
PUBLISHED: 06-18-2014
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Protein phosphatase 1 (PP1) is a major serine/threonine phosphatase that controls gene expression and cell cycle progression. The active mutant IPP5 (8-60hIPP5(m)), the latest member of the inhibitory molecules for PP1, has been shown to inhibit the growth of human cervix carcinoma cells (HeLa). In order to elucidate the underlying mechanisms, the present study assessed overexpression of 8-60hIPP5(m) in HeLa cells. Flow cytometric and biochemical analyses showed that overexpression of 8-60hIPP5(m) induced G2/M-phase arrest, which was accompanied by the upregulation of cyclin B1 and phosphorylation of G2/M-phase proteins ATM, p53, p21(cip1/waf1) and Cdc2, suggesting that 8-60hIPP5(m) induces G2/M arrest through activation of the ATM/p53/p21(cip1/waf1)/Cdc2/ cyclin B1 pathways. We further showed that overexpression of 8-60hIPP5(m) led to delayed nuclear translocation of cyclin B1. 8-60hIPP5(m) also could translocate to the nucleus in G2/M phase and interact with pp1? and Cdc2 as demonstrated by co-precipitation assay. Taken together, our data demonstrate a novel role for 8-60hIPP5(m) in regulation of cell cycle in HeLa cells, possibly contributing to the development of new therapeutic strategies for cervix carcinoma.
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[Expression pattern of genes involved in tropane alkaloids biosynthesis and tropane alkaloids accumulation in Atropa belladonna].
Zhongguo Zhong Yao Za Zhi
PUBLISHED: 04-24-2014
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Atropa belladonna is a medicinal plant and main commercial source of tropane alkaloids (TAs) including scopolamine and hyoscyamine, which are anticholine drugs widely used clinically. Based on the high throughput transcriptome sequencing results, the digital expression patterns of UniGenes representing 9 structural genes (ODC, ADC, AIH, CPA, SPDS, PMT, CYP80F1, H6H, TRII) involved in TAs biosynthesis were constructed, and simultaneously expression analysis of 4 released genes in NCBI (PMT, CYP80F1, H6H, TRII) for verification was performed using qPCR, as well as the TAs contents detection in 8 different tissues. Digital expression patterns results suggested that the 4 genes including ODC, ADC, AIH and CPA involved in the upstream pathway of TAs, and the 2 branch pathway genes including SPDS and TRII were found to be expressed in all the detected tissues with high expression level in secondary root. While the 3 TAs-pathway-specific genes including PMT, CYP80F1, H6H were only expressed in secondary roots and primary roots, mainly in secondary roots. The qPCR detection results of PMT, CYP80F1 and H6H were consistent with the digital expression patterns, but their expression levels in primary root were too low to be detected. The highest content of hyoscyamine was found in tender stems (3.364 mg x g(-1)), followed by tender leaves (1.526 mg x g(-1)), roots (1.598 mg x g(-1)), young fruits (1.271 mg x g(-1)) and fruit sepals (1.413 mg x g(-1)). The highest content of scopolamine was detected in fruit sepals (1.003 mg x g(-1)), then followed by tender stems (0.600 mg x g(-1)) and tender leaves (0.601 mg x g(-1)). Both old stems and old leaves had the lowest content of hyoscyamine and scopolamine. The gene expression profile and TAs accumulation indicated that TAs in Atropa belladonna were mainly biosynthesized in secondary root, and then transported and deposited in tender aerial parts. Screening Atropa belladonna secondary root transcriptome database will facilitate unveiling the unknown enzymatic reactions and the mechanisms of transcriptional control.
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Enhanced bioelectricity generation by improving pyocyanin production and membrane permeability through sophorolipid addition in Pseudomonas aeruginosa-inoculated microbial fuel cells.
Bioresour. Technol.
PUBLISHED: 04-12-2014
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Improvement on electron shuttle-mediated extracellular electron transfer (EET) is of great potential to enhance the power output of MFCs. In this study, sophorolipid was added to enhance the performance of Pseudomonas aeruginosa-inoculated MFC by improving the electron shuttle-mediated EET. Upon sophorolipid addition, the current density and power density increased ? 1.7 times and ? 2.6 times, respectively. In accordance, significant enhancement on pyocyanin production (the electron shuttle) and membrane permeability were observed. Furthermore, the conditions for sophorolipid addition were optimized to achieve maximum pyocyanin production (14.47 ± 0.23 ?g/mL), and 4 times higher power output was obtained compared to the control. The results substantiated that enhanced membrane permeability and pyocyanin production by sophorolipid, which promoted the electron shuttle-mediated EET, underlies the improvement of the energy output in the P. aeruginosa-inoculated MFC. It suggested that addition of biosurfactant could be a promising way to enhance the energy generation in MFCs.
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Fabrication and electrical properties of stacked graphene monolayers.
Sci Rep
PUBLISHED: 04-07-2014
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We develop a simple method to fabricate the two-stacked graphene monolayers and investigate the electronic transport in such a system. The independence of the two graphene monolayers gives rise to the asymmetric resistance-gate voltage curves and an eight-fold degeneracy of Landau level. The position of the maximum resistance of the transfer curves shifts towards higher gate voltage with increasing magnetic field, which is attributed to the magnetic field induced interlayer decoupling of the stacked graphene monolayers.
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Exciton drift in semiconductors under uniform strain gradients: application to bent ZnO microwires.
ACS Nano
PUBLISHED: 03-27-2014
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Optimizing the electronic structures and carrier dynamics in semiconductors at atomic scale is an essential issue for innovative device applications. Besides the traditional chemical doping and the use of homo/heterostructures, elastic strain has been proposed as a promising possibility. Here, we report on the direct observation of the dynamics of exciton transport in a ZnO microwire under pure elastic bending deformation, by using cathodoluminescence with high temporal, spatial, and energy resolutions. We demonstrate that excitons can be effectively drifted by the strain gradient in inhomogeneous strain fields. Our observations are well reproduced by a drift-diffusion model taking into account the strain gradient and allow us to deduce an exciton mobility of 1400 ± 100 cm(2)/(eV s) in the ZnO wire. These results propose a way to tune the exciton dynamics in semiconductors and imply the possible role of strain gradient in optoelectronic and sensing nano/microdevices.
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Two new sesquiterpenes from Artemisia sieversiana.
Fitoterapia
PUBLISHED: 03-26-2014
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Two new sesquiterpenes, together with 32 known compounds(3-34), were isolated from Artemisia sieversiana Ehrhart ex willd. and the compounds 3-21 were isolated from this plant for the first time. The new compounds were elucidated as 2?,9?-dihydroxymuurol-3(4)-en-12-oic acid (1) and 13?-methyl-(5?H,6?H,7?H,8?H)-austricin 8-O-?-D-glucopyranoside (2), respectively. The structural identification of these compounds was mainly achieved by spectroscopic methods including 1D and 2D NMR techniques, and the structure of compound 1 was confirmed by a single crystal X-ray diffraction experiment. Compounds 1-2 were evaluated for cytotoxic activity in vitro against MCF-7, NCI-H460 and Hep-G2 cell lines, respectively.
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Growth model for laser-induced damage on the exit surface of fused silica under UV, ns laser irradiation.
Opt Express
PUBLISHED: 03-26-2014
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We present a comprehensive statistical model which includes both the probability of growth and growth rate to describe the evolution of exit surface damage sites on fused silica optics over multiple laser shots spanning a wide range of fluences. We focus primarily on the parameterization of growth rate distributions versus site size and laser fluence using Weibull statistics and show how this model is consistent with established fracture mechanics concepts describing brittle materials. Key growth behaviors and prediction errors associated with the present model are also discussed.
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Bioinformatics analysis identifies miR-221 as a core regulator in hepatocellular carcinoma and its silencing suppresses tumor properties.
Oncol. Rep.
PUBLISHED: 03-21-2014
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Hepatocellular carcinoma (HCC) is a worldwide malignancy; however, there is a lack of effective targeted therapies. We and others have found that miR-221 is one of the most consistently overexpressed miRNAs in liver cancer. However, the roles of miR-221 in hepatocellular carcinogenesis are still not fully elucidated. In the present study, we used bioinformatics tools, gain- and loss-of-function methods to determine the roles of miR-221 in HCC. Bioinformatics analysis showed that miR-221 is a core miRNA which targets a large number of HCC-related genes and has formed many feed-forward regulatory loops combining transcription factors (TFs) to regulate HCC-related genes. Inhibition of miR-221 in liver cancer cells decreased cell proliferation, clonogenicity, migration/invasion and also induced G1 arrest and apoptosis. In addition, we demonstrated that miR-221 bound directly to the 3'-untranslated region of BMF, BBC3 and ANGPTL2, and inhibited the expression of BMF, BBC3 and ANGPTL2. In a mouse model, lentivirus?mediated miR-221 silencing could significantly suppress the growth of hepatoma xenografts in nude mice. In conclusion, we showed that miR-221 is a critical modulator in the HCC signaling pathway, and miR-221 silencing inhibits liver cancer malignant properties in vitro and in vivo, which may benefit the treatment for patients with unresectable HCC.
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Synthesis and antitumor activities of novel ?-aminophosphonate derivatives containing an alizarin moiety.
Eur J Med Chem
PUBLISHED: 02-19-2014
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A series of novel ?-aminophosphonate derivatives containing an alizarin moiety (6-7) was designed and synthesized as antitumor agents. MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide) assay results indicated that most compounds exhibited moderate to high inhibitory activity against KB, NCI-H460, HepG 2, A549, MGC-803, Hct-116, CNE and Hela tumor cell lines. The action mechanism of representative compounds 7h, 7j and 7n were investigated by fluorescence staining assays, flow cytometric analysis and real-time polymerase chain reaction (PCR) assays, which indicated that these compounds induced apoptosis and involved G1 phase arrest by increasing the production of intracellular Ca(2+) and reactive oxygen species (ROS) and affecting associated enzymes and genes. The results demonstrated that these compounds may induce apoptosis through a mitochondrion-dependent pathway.
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Two new diterpene derivatives from Euphorbia lunulata Bge and their anti-proliferative activities.
Fitoterapia
PUBLISHED: 01-15-2014
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A new ent-abietane-type diterpene lactone (1) and a new jatrophane-type diterpenoid (2), together with twelve known compounds including three diterpenes (3-5), five triterpenes (6-10) and four sterides (11-14) were isolated from the ethanol extract of the whole plant of Euphorbia lunulata Bge. The structure of compounds 1 and 2 was elucidated on the basis of 1D and 2D NMR spectra and the HR-ESI-MS data. The structure of compound 2 was further analyzed by an X-ray crystallographic study. The in vitro anti-proliferative activities against MCF-7 and NCI-H460 cell lines for compounds 1-5 (diterpene) were evaluated. The results showed marked activity for compound 1 against the two cell lines with the IC50 values 19.5 (NCI-H460) and 18.6 (MCF-7) ?M, while for cis-platinum (a positive cytotoxic control agent) 29.7 (NCI-H460) and 27.7 (MCF-7) ?M. Compounds 2-5 exhibited moderate cytotoxic activities for the two cell lines with the IC50 values ranging from 32.1 to 58.2 ?M.
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High-mobility Bi2Se3 nanoplates manifesting quantum oscillations of surface states in the sidewalls.
Sci Rep
PUBLISHED: 01-03-2014
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Magnetotransport measurements of topological insulators are very important to reveal the exotic topological surface states for spintronic applications. However, the novel properties related to the surface Dirac fermions are usually accompanied by a large linear magnetoresistance under perpendicular magnetic field, which makes the identification of the surface states obscure. Here, we report prominent Shubnikov-de Haas (SdH) oscillations under an in-plane magnetic field, which are identified to originate from the surface states in the sidewalls of topological insulator Bi2Se3 nanoplates. Importantly, the SdH oscillations appear with a dramatically weakened magnetoresistance background, offering an easy path to probe the surface states directly when the coexistence of surface states and bulk conduction is inevitable. Moreover, under a perpendicular magnetic field, the oscillations in Hall conductivity have peak-to-valley amplitudes of 2?e(2)/h, giving confidence to achieve a quantum Hall effect in this system. A cross-section view of the nanoplate shows that the sidewall is (015) facet dominant and therefore forms a 58° angle with regard to the top/bottom surface instead of being perpendicular; this gives credit to the surface states' behavior as two-dimensional transport.
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Sparse canonical correlation analysis: new formulation and algorithm.
IEEE Trans Pattern Anal Mach Intell
PUBLISHED: 10-19-2013
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In this paper, we study canonical correlation analysis (CCA), which is a powerful tool in multivariate data analysis for finding the correlation between two sets of multidimensional variables. The main contributions of the paper are: 1) to reveal the equivalent relationship between a recursive formula and a trace formula for the multiple CCA problem, 2) to obtain the explicit characterization for all solutions of the multiple CCA problem even when the corresponding covariance matrices are singular, 3) to develop a new sparse CCA algorithm, and 4) to establish the equivalent relationship between the uncorrelated linear discriminant analysis and the CCA problem. We test several simulated and real-world datasets in gene classification and cross-language document retrieval to demonstrate the effectiveness of the proposed algorithm. The performance of the proposed method is competitive with the state-of-the-art sparse CCA algorithms.
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Size-dependent correlations between strain and phonon frequency in individual ZnO nanowires.
ACS Nano
PUBLISHED: 09-20-2013
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The effect of uniaxial tensile strain on individual ZnO nanowires with diameters ranging from 500 nm to 2.7 ?m and the effect of pure bending strain on ZnO microwires are systematically investigated by Raman spectroscopy. It is found for the first time that the tensile and compressive strains result in a linear downshift and upshift of the phonon frequencies of the E2L, E2H, E1TO, and second-order modes compared with the strain-free state, respectively, while the A1TO mode is not influenced by the strain. Furthermore, the strain modulation on phonons depends strongly on the nanowire diameter. The E2H phonon deformation potential is ~3 cm(-1)/% for the 500 nm nanowire, while 1% tensile strain results only in ~1 cm(-1) downward frequency shift for the 2.7 ?m ZnO wire. The results provide a versatile "local-self-calibration" and nondestructive method to measure and monitor the local strains in ZnO micro/nanostructures.
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[Influence of recombinant lentiviral vector encoding miR-15a/16-1 in biological features of human nasopharyngeal carcinoma CNE-2Z cells].
Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi
PUBLISHED: 09-11-2013
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To study the influence of recombinant lentiviral vector encoding miR-15a/16-1 on biological features of human nasopharyngeal carcinoma CNE-2Z cells and underlying mechanisms.
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[Enhanced biosynthesis of scopolamine in transgenic Atropa belladonna by overexpression of h6h gene].
Zhongguo Zhong Yao Za Zhi
PUBLISHED: 09-10-2013
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Transgenic Atropa belladonna with high levels of scopolamine was developed by metabolic engineering. A functional gene involved in the rate limiting enzyme of h6h involved in the biosynthetic pathway of scopolamine was over expressed in A. belladonna via Agrobacterium-mediation. The transgenic plants were culturing till fruiting through micropropogating and acclimating. The integration of the h6h genes into the genomic DNA of transgenic plants were confirmed by genomic polymerase chain reaction (PCR) analysis. Analysis of the difference of plant height, crown width, stem diameter, leaf length, leaf width, branch number and fresh weight was carried out using SPSS software. The content of hyoscyamine and scopolamine in roots, stems, leaves and fruits was determined by HPLC. The investigation of the expression levels of Hnh6h by qPCR. Both Kan(r) and Hnh6h genes were detected in five transgenic lines of A. belladonna plants (A8, A11, A12, C8 and C19), but were not detected in the controls. The plant height, crown width, stem diameter, leaf length, leaf width, branch number and fresh weight of transgenic plants did not decrease by comparison with the non-transgenic ones, and furthermore some agronomic characters of transgenic plants were better than those of the controls. The highest level of scopolamine was found in leaves of transgenic A. belladonna, and the content of scopolamine was also higher than that of hyoscyamine in leaves. The contents of scopolamine of leaves in different transgenic lines were listed in order: C8 > A12 > C19 > A11 > A8, especially, the content of scopolamine in transgenic line C8 was 2.17 mg x g(-1) DW that was 4.2 folds of the non-transgenic ones (0.42 mg x g(-1) DW). The expression of transgenic Hnh6h was detected in all the transgenic plants but not in the control. The highest level of Hnh6h expression was found in transgenic leaves. Overexpression of Hnh6h is able to break the rate limiting steps involved in the downstream pathway of scopolamine biosynthesis, and thus promotes the metabolic flux flowing toward biosynthesis of scopolamine to improve the capacity of scopolamine biosynthesis in transgenic plants. As a result, transgenic plants of A. belladonna with higher level of scopolamine were developed.
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Synthesis and antitumor activities of novel rhein ?-aminophosphonates conjugates.
Bioorg. Med. Chem. Lett.
PUBLISHED: 08-29-2013
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Several rhein ?-aminophosphonates conjugates (5a-5q) were synthesized and evaluated for in vitro cytotoxicity against HepG-2, CNE, Spca-2, Hela and Hct-116 cell lines. Some compounds showed relatively high cytotoxicity. Especially, compound 5i exhibited the strongest cytotoxicity against Hct-116 cells (IC50 was 5.32?M). All the synthesized compounds exhibited low cytotoxicity against HUVEC cells. The mechanism of compound 5i was preliminarily investigated by Hoechst 33258 staining, JC-1 mitochondrial membrane potential staining and flow cytometry, which indicated that the compound 5i induced apoptosis in Hct-116 cancer cells. Cell cycle analysis showed that these compound 5i mainly arrested Hct-116 cells in G1 stage. The effects of 5i on the activation of caspases expression indicated that 5i might induce apoptosis via the membrane death receptor pathways. In addition, the binding properties of a model analog 5i to DNA were investigated by methods (UV-vis, fluorescence, CD spectroscopy and FRET-melting) in compare with that of rhein. Results indicated that 5i showed moderate ability to interact ct-DNA.
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Vertical graphene spin valve with Ohmic contacts.
Nanoscale
PUBLISHED: 08-01-2013
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Evident spin valve signals are observed in Co/graphene/Co sandwich structures with both monolayer and two-layer graphene stacks at temperatures from 1.5 K to 300 K. All the devices demonstrate linear current-voltage curves, indicating that an Ohmic property is dominating rather than a tunneling effect. The vertical graphene spin valves have potential applications in high-density non-volatile memories.
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Reversible insulator-metal transition of LaAlO?/SrTiO? interface for nonvolatile memory.
Sci Rep
PUBLISHED: 07-29-2013
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We report a new type of memory device based on insulating LaAlO?/SrTiO? (LAO/STO) hetero-interface. The microstructures of the LAO/STO interface are characterized by Cs-corrected scanning transmission electron microscopy, which reveals the element intermixing at the interface. The inhomogeneous element distribution may result in carrier localization, which is responsible for the insulating state. The insulating state of such interface can be converted to metallic state by light illumination and the metallic state maintains after light off due to giant persistent photoconductivity (PPC) effect. The on/off ratio between the PPC and the initial dark conductance is as large as 10?. The metallic state also can be converted back to insulating state by applying gate voltage. Reversible and reproducible resistive switching makes LAO/STO interface promising as a nonvolatile memory. Our results deepen the understanding of PPC phenomenon in LAO/STO, and pave the way for the development of all-oxide electronics integrating information storage devices.
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Synthesis and antitumor activity evaluation of maleopimaric acid N-aryl imide atropisomers.
Bioorg. Med. Chem. Lett.
PUBLISHED: 07-25-2013
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Maleopimaric acid N-aryl imides (2) and methyl maleopimaric acid N-aryl imides (3) were designed and synthesized. Their atropisomers (A and B) were separated into their enantiomeric pure forms and the anti-proliferative activity was tested against NCI, A549, Hep G-2, MGC-803 and Hct-116 cell lines, respectively. A significant difference in the level of cytotoxicity was observed between R and S conformers. Atropisomers A with an R configuration exhibited significant toxicity (the IC50 values ranging from 7.51 to 32.1?M). Further experiments proved that antitumor activity of 2A was achieved through the induction of cell apoptosis by G1 cell-cycle arrest.
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Sparse Canonical Correlation Analysis: New Formulation and Algorithm.
IEEE Trans Pattern Anal Mach Intell
PUBLISHED: 05-29-2013
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In this paper, we study canonical correlation analysis (CCA), which has become a powerful tool in multivariate data analysis for finding the correlations between two sets of multidimensional variables. The main contributions of the paper are: (i) to reveal the equivalent relationship between a recursive formula and a trace formula for the multiple CCA problem; (ii) to obtain the explicit characterization of all solutions for the multiple CCA problem even the covariance matrices are singular; (iii) to develop a new sparse CCA algorithm; and (iv) to establish the equivalent relationship between the uncorrelated linear discriminant analysis and the CCA problem. We test several simulated and real world data sets in gene classification and cross-language document retrieval to demonstrate the effectiveness of the proposed algorithm. The performance of the proposed method is competitive with the state-of-the-art sparse CCA algorithms.
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Graphene plasmon enhanced photoluminescence in ZnO microwires.
Nanoscale
PUBLISHED: 05-23-2013
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We report the temperature dependent photoluminescence (PL) properties of monolayer graphene-Au-nanoparticle-ZnO (GAZ) microwire hybrid structures. By comparing with the bare ZnO wire without coverage of graphene, a three times enhancement of PL was found in the GAZ hybrid structures. The enhancement is attributed to the coupling between the PL photons from ZnO and the graphene surface plasmons with ~1-2 nm Au as a corrugated surface. Our results may be valuable for designing graphene-ZnO hybrid based optical and photoelectrical devices.
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[Enhancement of tropane alkaloids production in transgenic hair roots of Atropa belladonna by overexpressing endogenous genes AbPMT and AbH6H].
Yao Xue Xue Bao
PUBLISHED: 05-16-2013
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Atropa belladonna L. is the officially medicinal plant species and the main commercial source of scopolamine and hyoscyamine in China. In this study, we reported the simultaneous overexpression of two functional genes involved in biosynthesis of scopolamine, which respectively encoded the upstream key enzyme putrescine N-methyltransferase (PMT; EC 2.1.1.53) and the downstream key enzyme hyoscyamine 6beta-hydroxylase (H6H; EC 1.14.11.11) in transgenic hair root cultures of Atropa belladonna L. HPLC results suggested that four transgenic hair root lines produced higher content of scopolamine at different levels compared with nontransgenic hair root cultures. And scopolamine content increased to 8.2 fold in transgenic line PH2 compared with that of control line; and the other four transgenic lines showed an increase of scopolamine compared with the control. Two of the transgenic hair root lines produced higher levels of tropane alkaloids, and the content increased to 2.7 fold in transgenic line PH2 compared with the control. The gene expression profile indicated that both PMT and H6H expressed at a different levels in different transgenic hair root lines, which would be helpful for biosynthesis of scopolamine. Our studies suggested that overexpression of A. belladonna endogenous genes PMT and H6H could enhance tropane alkaloid biosynthesis.
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Evolutionary increases in defense during a biological invasion.
Oecologia
PUBLISHED: 05-07-2013
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Invasive plants generally escape from specialist herbivores of their native ranges but may experience serious damage from generalists. As a result, invasive plants may evolve increased resistance to generalists and tolerance to damage. To test these hypotheses, we carried out a common garden experiment comparing 15 invasive populations with 13 native populations of Chromolaena odorata, including putative source populations identified with molecular methods and binary choice feeding experiments using three generalist herbivores. Plants from invasive populations of C. odorata had both higher resistance to three generalists and higher tolerance to simulated herbivory (shoot removal) than plants from native populations. The higher resistance of plants from invasive populations was associated with higher leaf C content and densities of leaf trichomes and glandular scales, and lower leaf N and water contents. Growth costs were detected for tolerance but not for resistance, and plants from invasive populations of C. odorata showed lower growth costs of tolerance. Our results suggest that invasive plants may evolve to increase both resistance to generalists and tolerance to damage in introduced ranges, especially when the defense traits have low or no fitness costs. Greater defenses in invasive populations may facilitate invasion by C. odorata by reducing generalist impacts and increasing compensatory growth after damage has occurred.
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[Short-course kidney-invigorating therapy improves near-term semen quality in asthenozoospermic men with kidney deficiency].
Zhonghua Nan Ke Xue
PUBLISHED: 02-28-2013
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To evaluate the effect of short-course kidney-invigorating therapy on near-term semen quality in asthenozoospermic men with kidney deficiency.
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Ultraviolet irradiation-controlled memory effect in graphene field-effect transistors.
Small
PUBLISHED: 02-11-2013
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Control of graphene memory devices using photons, via control of the charge-transfer process, is demonstrated by employing gate-voltage pulses to program/erase the memory elements. The hysteresis in the conductance-gate voltage-dependence of graphene field-effect transistors on a SiO2 substrate can be greatly enlarged by ultraviolet irradiation in both air and vacuum. An enhanced charge transfer between graphene and its surroundings, induced by ultraviolet illumination, is proposed.
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HDAC6 promotes hepatocellular carcinoma progression by inhibiting P53 transcriptional activity.
FEBS Lett.
PUBLISHED: 02-01-2013
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Hepatocellular carcinoma (HCC) is the most common type of liver cancer. HDAC6 is a transcriptional regulator of the histone deacetylase family, subfamily 2. Previous studies have shown that HDAC6 plays critical roles in transcription regulation, cell cycle progression and developmental events. However, its biological roles in the development of HCC remain largely unexplored. In the present study, we found that mRNA and protein levels of HDAC6 were up-regulated in HCC tissues and cell lines. The proinflammatory cytokines, which were up-regulated in the human HCC microenvironment, increased HDAC6 expression through a proximal NF-kappaB binding site on the HDAC6 gene promoter. Furthermore, overexpression of HDAC6 could promote cell proliferation in HCC cell lines. In contrast, HDAC6 knockdown using small interfering RNA inhibited cell proliferation. At the molecular level, we demonstrated that HDAC6 could interact with p53 and attenuate its transcriptional activity through promotion of its degradation. Therefore, our results suggest a previously unknown HDAC6-p53 molecular network controlling HCC development.
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Synthesis, cytotoxicity, DNA binding and apoptosis of rhein-phosphonate derivatives as antitumor agents.
Int J Mol Sci
PUBLISHED: 01-31-2013
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Several rhein-phosphonate derivatives (5a-c) were synthesized and evaluated for in vitro cytotoxicity against HepG-2, CNE, Spca-2, Hela and Hct-116 cell lines. Some compounds showed relatively high cytotoxicity. Especially compounds 5b exhibited the strongest cytotoxicity against HepG-2 and Spca-2 cells (IC50 was 8.82 and 9.01 µM), respectively. All the synthesized compounds exhibited low cytotoxicity against HUVEC cells. Further experiments proved that 5b could disturb the cell cycle in HepG-2 cells and induce apoptosis. In addition, the binding properties of a model conjugate 5b to DNA were investigated by methods (UV-Vis, fluorescence, CD spectroscopy). Results indicated that 5b showed moderate ability to interact ct-DNA.
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Stretch-induced stiffness enhancement of graphene grown by chemical vapor deposition.
ACS Nano
PUBLISHED: 01-28-2013
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The mechanical properties of ultrathin membranes have attracted considerable attention recently. Nanoindentation based on atomic force microscopy is commonly employed to study mechanical properties. We find that the data processing procedures in previous studies are nice approximations, but it is difficult for them to illustrate the mechanical properties precisely. Accordingly, we develop a revised numerical method to describe the force curve properly, by which the intrinsic mechanical properties of these membranes can be acquired. Combining the nanoindentation measurements with the revised numerical method, we demonstrate that loading-unloading cycles under large load can lead to a pronounced improvement in stiffness of graphene grown by chemical vapor deposition (CVD). The Youngs moduli of the stretched CVD graphene membranes can be improved to ?1 TPa, closing to the value of the pristine graphene. Our findings demonstrate a possible way to recover the exceptional elastic properties of CVD graphene from the softened stiffness caused by wrinkles.
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Synthesis and quantum transport properties of Bi?Se? topological insulator nanostructures.
Sci Rep
PUBLISHED: 01-14-2013
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Bi?Se? nanocrystals with various morphologies, including nanotower, nanoplate, nanoflake, nanobeam and nanowire, have been synthesized. Well-distinguished Shubnikov-de Haas (SdH) oscillations were observed in Bi?Se? nanoplates and nanobeams. Careful analysis of the SdH oscillations suggests the existence of Berrys phase ?, which confirms the quantum transport of the surface Dirac fermions in both Bi?Se? nanoplates and nanobeams without intended doping. The observation of the singular quantum transport of the topological surface states implies that the high-quality Bi?Se? nanostructures have superiorities for investigating the novel physical properties and developing the potential applications.
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Layer-by-layer assembly of vertically conducting graphene devices.
Nat Commun
PUBLISHED: 01-07-2013
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Graphene has various potential applications owing to its unique electronic, optical, mechanical and chemical properties, which are primarily based on its two-dimensional nature. Graphene-based vertical devices can extend the investigations and potential applications range to three dimensions, while interfacial properties are crucial for the function and performance of such graphene vertical devices. Here we report a general method to construct graphene vertical devices with controllable functions via choosing different interfaces between graphene and other materials. Two types of vertically conducting devices are demonstrated: graphene stacks sandwiched between two Au micro-strips, and between two Co layers. The Au|graphene|Au junctions exhibit large magnetoresistance with ratios up to 400% at room temperature, which have potential applications in magnetic field sensors. The Co|graphene|Co junctions display a robust spin valve effect at room temperature. The layer-by-layer assembly of graphene offers a new route for graphene vertical structures.
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Norlathyrane diterpenes from the root of Euphorbia kansuensis.
Chem. Biodivers.
PUBLISHED: 01-05-2013
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Phytochemical investigation of the EtOH extract obtained from the root of the Euphorbia kansuensis Proch. grown in China resulted in the isolation of two novel norlathyrane diterpenes, named ekanpenoids A and B (1 and 2, resp.). Their structures were established by extensive 1D- and 2D-NMR spectroscopy, as well as other spectra. The isolated diterpenes exhibited potent cytotoxic activities against the HeLa and Hep-G2 cell lines with the IC50 values ranging from 3.6 to 9.7??g/ml.
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Triterpenoids of Chrysosplenium carnosum.
Fitoterapia
PUBLISHED: 01-05-2013
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A phytochemical study of the ethanolic extract of Chrysosplenium carnosum Hook. f. et Thoms. led to the isolation of two new oleanane-type triterpenoids, 6?-hydroxy-3-oxoolean-12-en-27-oic acid (1) and 3?, 21?-dihydroxyolean-12-en-27-oic acid (2), along with fourteen known compounds (3-16), all of which were isolated from this plant for the first time. The structures of these compounds were established on the basis of spectroscopic methods. Compounds 1-4 were evaluated for their in vitro anti-tumor activities on B16F10, SP2/0 and Hep-G2 cells lines. Compounds 1, 3 and 4 exhibited strong inhibitory activity against B16F10 and SP2/0 cells growth, compared with moderate cytotoxic activity against Hep-G2 cells. However, compound 2 showed to be inactive against these tumor cells.
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Improvement of ultraviolet photoresponse of bent ZnO microwires by coupling piezoelectric and surface oxygen adsorption/desorption effects.
Nanoscale
PUBLISHED: 01-04-2013
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Localized ultraviolet photoresponse properties of bent ZnO microwires bridging two perfect Ohmic contacts in both atmospheric and high vacuum (8 × 10(-6) torr) environments have been investigated for the first time to explore the bending strain effect on the photoelectrical properties of ZnO. It is found that the ZnO microwire has higher photoconductivity and faster rising speed when photo-excitation is localized at the bending region in an atmospheric environment, while the rising speeds are almost the same when photo-excitations are localized at the bending and straight regions under vacuum. The bending strain induced improvement of the UV photoresponse in air was well explained by considering the coupling of piezoelectric effects and the surface oxygen adsorption/desorption procedure on the bent ZnO microwire. Our results are valuable for designing and fabricating strain modulated photoelectrical micro/nano-devices.
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Differences in competitive ability between plants from nonnative and native populations of a tropical invader relates to adaptive responses in abiotic and biotic environments.
PLoS ONE
PUBLISHED: 01-01-2013
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The evolution of competitive ability of invasive plant species is generally studied in the context of adaptive responses to novel biotic environments (enemy release) in introduced ranges. However, invasive plants may also respond to novel abiotic environments. Here we studied differences in competitive ability between Chromolaena odorata plants of populations from nonnative versus native ranges, considering biogeographical differences in both biotic and abiotic environments. An intraspecific competition experiment was conducted at two nutrient levels in a common garden. In both low and high nutrient treatments, C. odorata plants from nonnative ranges showed consistently lower root to shoot ratios than did plants from native ranges grown in both monoculture and competition. In the low nutrient treatment, C. odorata plants from nonnative ranges showed significantly lower competitive ability (competition-driven decreases in plant height and biomass were more), which was associated with their lower root to shoot ratios and higher total leaf phenolic content (defense trait). In the high nutrient treatment, C. odorata plants from nonnative ranges showed lower leaf toughness and cellulosic contents (defense traits) but similar competitive ability compared with plants from native ranges, which was also associated with their lower root to shoot ratios. Our results indicate that genetically based shifts in biomass allocation (responses to abiotic environments) also influence competitive abilities of invasive plants, and provide a first potential mechanism for the interaction between range and environment (environment-dependent difference between ranges).
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[Nanoleakage at the resin-dental interface of four self-etching adhesives].
Zhonghua Kou Qiang Yi Xue Za Zhi
PUBLISHED: 12-20-2011
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To evaluate the nanoleakage and ultramorphology of four self-etching adhesives.
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[Experimental study on pulp revitalization of Beagle dogs immature permanent teeth after pulpectomy].
Zhonghua Kou Qiang Yi Xue Za Zhi
PUBLISHED: 12-16-2011
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To observe the process of pulp revitalization of immature permanent teeth after pulpectomy.
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[Evaluation of schistosomiasis control effect of buffalo removal in Anxiang County].
Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi
PUBLISHED: 11-30-2011
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To evaluate the effect of a comprehensive schistosomiasis control strategy based on buffalo removal in a lake and marshland region.
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[Solution structure and antibacterial mechanism of two synthetic antimicrobial peptides].
Sheng Wu Gong Cheng Xue Bao
PUBLISHED: 11-22-2011
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Mytilin-derived-peptide-1 (MDP-1) and mytilin-derived-peptide-2 (MDP-2) are two truncated decapeptides with reversed sequence synthesized corresponding to the residues 20-29 of mytilin-1 (GenBank Accession No. FJ973154) from M. coruscus. The objective of this study is to characterize the structural basis of these two peptides for their antimicrobial activities and functional differences, and to investigate the inhibitory mechanism of MDPs on Escherichia coli and Sarcina lutea. The structures of MDP-1 and MDP-2 in solution were determined by 1H 2D NMR methods; the antibactericidal effects of MDPs on E. coli and S. lutea were observed by transmitted electron microscopy (TEM). Both MDP-1 and MDP-2 have a well-defined loop structure stabilized by two additional disulfide bridges, which resemble the-hairpin structure of mytilin-1 model. The surface profile of MDPs structures was characterized by protruding charged residues surrounded by hydrophobic residues. TEM analysis showed that MDPs destroyed cytoplasmic membrane and cell wall of bacteria and the interface between the cell wall and membrane was blurred. Furthermore, some holes were observed in treated bacteria, which resulted in cell death. Structural comparison between MDP-1 and MDP-2 shows that the distribution of positively charged amino acids on the loop of MDPs is topologically different significantly, which might be the reason why MDP-2 has higher activity than MDP-1. Furthermore, TEM results suggested that the bactericidal mechanisms of MDPs against E. coli and S. lutea were similar. Both MDP-1 and MDP-2 could attach to the negatively charged bacterial wall by positively charged amino acid residues and destroy the bacteria membrane in a pore-forming manner, thus cause the contents of the cells to release and eventually cell death.
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Nanorainforest solar cells based on multi-junction hierarchical p-Si/n-CdS/n-ZnO nanoheterostructures.
Nanoscale
PUBLISHED: 11-11-2011
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Solar cells based on one-dimensional nanostructures have recently emerged as one of the most promising candidates to achieve high-efficiency solar energy conversion due to their reduced optical reflection, enhanced light absorption, and enhanced carrier collection. In nature, the rainforest, consisting of several stereo layers of vegetation, is the highest solar-energy-using ecosystem. Herein, we gave an imitation of the rainforest configuration in nanostructure-based solar cell design. Novel multi-layer nanorainforest solar cells based on p-Si nanopillar array/n-CdS nanoparticles/n-ZnO nanowire array heterostructures were achieved via a highly accessible, reproducible and controllable fabrication process. By choosing materials with appropriate bandgaps, an efficient light absorption and enhanced light harvesting were achieved due to the wide range of the solar spectrum covered. Si nanopillar arrays were introduced as direct conduction pathways for photon-generated charges efficient collection and transport. The unique strategy using PMMA as a void-filling material to obtain a continuous, uniform and low resistance front electrode has significantly improved the overall light conversion efficiency by two orders of magnitude. These results demonstrate that nanorainforest solar cells, along with wafer-scale, low-cost and easily controlled processing, open up substantial opportunities for nanostructure photovoltaic devices.
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[Rosuvastatin improves myocardial function and arteriosclerosis plaque in patients with ST-segment elevation after acute myocardial infarction and percutaneous coronary intervention].
Nan Fang Yi Ke Da Xue Xue Bao
PUBLISHED: 10-27-2011
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To evaluate the effect of rosuvastatin on the functions of the surviving myocardium and arteriosclerosis plaque in patients with ST-segment elevation after acute myocardial infarction (STEMI) and percutaneous coronary intervention (PCI).
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Memory and threshold resistance switching in Ni/NiO core-shell nanowires.
Nano Lett.
PUBLISHED: 10-13-2011
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We report on the first controlled alternation between memory and threshold resistance switching (RS) in single Ni/NiO core-shell nanowires by setting the compliance current (I(CC)) at room temperature. The memory RS is triggered by a high I(CC), while the threshold RS appears by setting a low I(CC), and the Reset process is achieved without setting a I(CC). In combination with first-principles calculations, the physical mechanisms for the memory and threshold RS are fully discussed and attributed to the formation of an oxygen vacancy (Vo) chain conductive filament and the electrical field induced breakdown without forming a conductive filament, respectively. Migration of oxygen vacancies can be activated by appropriate Joule heating, and it is energetically favorable to form conductive chains rather than random distributions due to the Vo-Vo interaction, which results in the nonvolatile switching from the off- to the on-state. For the Reset process, large Joule heating reorders the oxygen vacancies by breaking the Vo-Vo interactions and thus rupturing the conductive filaments, which are responsible for the switching from on- to off-states. This deeper understanding of the driving mechanisms responsible for the threshold and memory RS provides guidelines for the scaling, reliability, and reproducibility of NiO-based nonvolatile memory devices.
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Stability and convergence analysis for a class of neural networks.
IEEE Trans Neural Netw
PUBLISHED: 09-29-2011
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In this paper, we analyze and establish the stability and convergence of the dynamical system proposed by Xia and Feng, whose equilibria solve variational inequality and related problems. Under the pseudo-monotonicity and other conditions, this system is proved to be stable in the sense of Lyapunov and converges to one of its equilibrium points for any starting point. Meanwhile, the global exponential stability of this system is also shown under some mild conditions without the strong monotonicity of the mapping. The obtained results improve and correct some existing ones. The validity and performance of this system are demonstrated by some numerical examples.
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In situ growth, structure characterization, and enhanced photocatalysis of high-quality, single-crystalline ZnTe/ZnO branched nanoheterostructures.
Nanoscale
PUBLISHED: 09-19-2011
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Single-crystalline, high-quality branched ZnTe-core/ZnO-branch nanoheterostructures were synthesized by an in situ strategy in an environmental scanning electron microscope. Composition and structure characterization confirmed that ZnO nanowires were perfectly epitaxially grown on ZnTe nanowires as branches. Noticeably, growth temperature plays a crucial role in determining the density and diameter of the ZnO nanobranches on ZnTe nanowires: a higher growth temperature leads to ZnO nanowires with higher density and smaller diameter. It was demonstrated that ZnO nanobranches exhibited a selective nucleation behavior on distinct side facets of ZnTe nanowires. Highly ordered ZnO nanobranches were found epitaxially grown on {211} facet of ZnTe nanowires, while there was no ZnO nanowire growth on {110} facet of ZnTe nanowires. Using first-principles calculation, we found that surface energy of distinct side facets has a strong impact on ZnO nucleation, and confirm that {211} facet of ZnTe nanowires is energetically more favorable for ZnO nanowire growth than {110} facet, which is in good agreement with our experimental findings. Remarkably, such unique ZnTe/ZnO 3D branched nanowire heterostructures exhibited improved photocatalytic abilities, superior to ZnO nanowires and ZnTe nanowires, due to the much enhanced effective surface area of their unique architecture and effective electron-hole separation at the ZnTe/ZnO interfaces.
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Chemical constituents of Caryopteris tangutica.
Nat. Prod. Res.
PUBLISHED: 08-23-2011
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A new compound (1), along with 18 known compounds, was isolated from Caryopteris tangutica. On the basis of spectroscopic methods, with special emphasis on 1D- and 2D-NMR techniques, the structure of the new compound was characterised as 6-hydroxy-6-methylcyclohex-2-en-1-one (1).
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Improved performance of ZnO nanowire field-effect transistors via focused ion beam treatment.
Nanotechnology
PUBLISHED: 08-18-2011
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A seven orders of magnitude increase in the current on/off ratio of ZnO nanowire field-effect transistors (FETs) after Ga( + ) irradiation was observed. Transmission electron microscopy characterization revealed that the surface crystal quality of the ZnO nanowire was improved via the Ga( + ) treatment. The Ga( + ) irradiation efficiently reduces chemisorption effects and decreases oxygen vacancies in the surface layer. The enhanced performance of the nanowire FET was attributed to the decrease of surface trapped electrons and the decrease in carrier concentration.
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Exploration of the multiparameter space of nanosecond-laser damage growth in fused silica optics.
Appl Opt
PUBLISHED: 08-12-2011
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Historically, the rate at which laser-induced damage sites grow on the exit surface of SiO2 optics under subsequent illumination with nanosecond-laser pulses of any wavelength was believed to depend solely on laser fluence. We demonstrate here that much of the scatter in previous growth observations was due to additional parameters that were not previously known to affect growth rate, namely the temporal pulse shape and the size of a site. Furthermore, the remaining variability observed in the rate at which sites grow is well described in terms of Weibull statistics. The effects of site size and laser fluence may both be expressed orthogonally in terms of Weibull coefficients. In addition, we employ a clustering algorithm to explore the multiparameter growth space and expose average growth trends. Conversely, this analysis approach also identifies sites likely to exhibit growth rates outside the norm. The ability to identify which sites are likely to grow abnormally fast in advance of the manifestation of such behavior will significantly enhance the accuracy of predictive models over those based on average growth behaviors.
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[A comparative study of CT virtual endoscopy imaging and pathologies of lower alimentary tract mesenchymal tumors].
Zhonghua Nei Ke Za Zhi
PUBLISHED: 07-26-2011
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To study the pathological and immunohistochemical features of alimentary tract mesenchymal tumors and compare with computed tomographic virtue endoscopy (CTVE) imaging technology to evaluate the diagnostic value of CTVE in alimentary tract mesenchymal tumors.
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Modeling max-of-N fluence distribution using measured shot-to-shot beam contrast.
Appl Opt
PUBLISHED: 07-12-2011
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We have found the local temporal shot-to-shot variation of the NIF high-energy laser system to be relatively constant (~3.4% to 4.2% of the mean fluence). We have developed a statistical model that predicts the maximum fluence distribution any particular location will be exposed to after N independent shots (the so-called max-of-N fluence distribution) using the measured shot-to-shot variance; this method allows for an estimate of maximum optics fluence exposure.
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Purification, cDNA clone and recombinant expression of foot protein-3 from Mytilus coruscus.
Protein Pept. Lett.
PUBLISHED: 03-04-2011
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Mussels Mytilus coruscus can adhere to various solid surface in the presence of moisture. Mussel foot protein-3 (mfp-3) has been suggested as the main adhesive protein in the plaques closest to the adhesion interface and been the focus of substantial biomaterials development research within the last decade. The byssal plaques of M. coruscus were accumulated and variants of a family known as mcofp3 (Mytilus coruscus foot protein 3) were purified from acetic acid/urea extracts of plaques, with their N-terminal sequences determined thereafter. The cDNA sequence coding for the mcofp3 precursor was obtained from M. coruscus foot cDNA library. These precursors contain a putative signal peptide of 24 residues, a mature peptide sequence of 41-56 amino acids rich in Tyr, Gly, Pro, and Asn. The recombinant mcofp3 fused with a hexa-histidine affinity ligand was successfully expressed through an Escherichia coli expression system, and the recombinant mcofp3 was purified using affinity chromatography followed by reverse phase high performance liquid chromatography (HPLC). The DOPA content and adhesive properties of purified recombinant mcofp3 with or without tyrosinase modification were compared with the native mcofp3. These assays showed that recombinant mcofp3 has significant adhesive ability and may be useful as a bioadhesive in medical or underwater environments.
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Phenylpropanoid glycosides and triterpenoid of Pedicularis kansuensis Maxim.
Fitoterapia
PUBLISHED: 03-03-2011
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Phytochemical investigation of the ethanol extract of Pedicularis kansuensis Maxim. led to the isolation of one new triterpenoid and two new phenylpropanoid glycosides, along with ten known compounds. Their structures were established by extensive 1D and 2D NMR, as well as other spectrum analysis. Biological evaluation of the three new compounds against Hela cell and Hep-6 cell with MIC values ranging from 9 to 20 ?g/ml.
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Ion irradiation induced structural and electrical transition in graphene.
J Chem Phys
PUBLISHED: 12-29-2010
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The relationship between the electrical properties and structure evolution of single layer graphene was studied by gradually introducing the gallium ion irradiation. Raman spectrums show a structural transition from nano-crystalline graphene to amorphous carbon as escalating the degree of disorder of the graphene sample, which is in correspondence with the electrical transition from a Boltzmann diffusion transport to a carrier hopping transport. The results show a controllable method to tune the properties of graphene.
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Self-powered, ultrafast, visible-blind UV detection and optical logical operation based on ZnO/GaN nanoscale p-n junctions.
Adv. Mater. Weinheim
PUBLISHED: 08-31-2010
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Ultrafast-response (20 ?s) UV detectors, which are visible-blind and self-powered, in devices where an n-type ZnO nanowire partially lies on a p-type GaN film, are demonstrated. Moreover, a CdSe-nanowire red-light detector powered by a nanoscale ZnO/GaN photovoltaic cell is also demonstrated, which extends the device function to a selective multiwavelength photodetector and shows the function of an optical logical AND gate.
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Recurrence of hepatocellular carcinoma after liver transplantation: recurrence characteristics and risk factors.
Hepatogastroenterology
PUBLISHED: 08-12-2010
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The aim of this study was to investigate tumor recurrence characteristics of hepatocellular carcinoma (HCC) after liver transplantation (LT), including recurrence sites, time and risk factors, and to provide a basis for predicting and preventing tumor recurrence.
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Hysteresis reversion in graphene field-effect transistors.
J Chem Phys
PUBLISHED: 08-07-2010
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To enhance performances of graphene/SiO(2) based field-effect transistors (FETs), understanding of the transfer of carriers through the graphene/SiO(2) interface is crucial. In this paper, we have studied the temperature dependent transfer characters of graphene FETs. Hysteresis loop is shown to be dominated by trapping/detrapping carriers through the graphene/SiO(2) interface.
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Accelerated partial breast irradiation: Use of four-dimensional CT for target localization and assessment of intrafractional motion.
Oncol. Res.
PUBLISHED: 08-05-2010
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The aim of this study was to use four-dimensional CT (4DCT) in the planning of 3D conformational external beam radiation therapy (3DCRT) for patients with early stage breast cancer. A total of nine Chinese women who received breast conservation treatment were included in this study. Target localization and movement (range of motion) during normal respiration were assessed using ultrasound and 4DCT. Plans based on 3DCT and 4DCT scans were developed in accordance to RTOG0319 guidelines and dose delivery comparisons were made between these plans. The mean ranges of motion of the excision cavity volume as determined using 4DCT were 1.03 +/- 0.51, 2.08 +/- 0.92, and 1.27 +/- 0.58 mm in the right-left, anterior-posterior, and superior-interior directions, respectively. There were no significant differences between the mean and maximum PTV-E doses or the volume receiving 95% of the prescribed dose (V95). 4D plan prescribed dose levels were significantly lower (p < 0.05) than 3D plan levels for all of the following: ipsilateral breast V100, ipsilateral lung V30, and contralateral lung V5. Maximum contralateral breast and thyroid doses were also significantly lower with the 4D plan (p < 0.05). This study highlights the usefulness of 4DCT for the planning of 3DCRT in breast cancer patients. Our findings suggest that the use of 4DCT can lead to improvements in target definition and decreases in normal tissues irradiation.
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Predicting laser-induced bulk damage and conditioning for deuterated potassium dihydrogen phosphate crystals using an absorption distribution model.
Opt Lett
PUBLISHED: 08-04-2010
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We present an empirical model that describes the experimentally observed laser-induced bulk damage and conditioning behavior in deuterated potassium dihydrogen phosphate (DKDP) crystals. The model expands on an existing nanoabsorber precursor model and the multistep absorption mechanism to include two populations of absorbing defects, one with linear absorption and another with nonlinear absorption. We show that this model connects previously uncorrelated small-beam damage initiation probability data to large-beam damage density measurements over a range of nanosecond pulse widths. In addition, this work predicts the damage behavior of laser-conditioned DKDP.
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[Designation, solid-phase synthesis and antimicrobial activity of Mytilin derived peptides based on Mytilin-1 from Mytilus coruscus].
Sheng Wu Gong Cheng Xue Bao
PUBLISHED: 06-26-2010
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As a key role in mussel defense system, Mytilin is an important antibacterial peptide isolated from the mussel serum. The structural and functional researches on Mytilin showed that the fragment connecting two beta-sheets in a stable beta-hairpin structure was probably required for antimicrobial activity. To elucidate the structural features and the antimicrobial activity of this fragment, we re-designed and synthesized two peptides corresponding to the main mimic structures of Mytilin-1 from Mytilus coruscus, we named these two peptides Mytilin Derived Peptide-1 and Mytilin Derived Peptide-2, respectively. Using a liquid growth inhibition assay, we evaluated their activity towards Gram-positive, Gram-negative bacteria and fungus. The results showed that both peptides can inhibit the growth of Gram-positive, Gram-negative bacteria and fungus. Besides, these two peptides showed high stability in heat water and human serum. These works laid the foundation for further research on the molecular mechanism of Mytilin and for further exploitation of antibacterial peptides with lower molecular mass and more stable structure.
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