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Find video protocols related to scientific articles indexed in Pubmed.
Comparing and combining capillary electrophoresis electrospray ionization mass spectrometry and nano-liquid chromatography electrospray ionization mass spectrometry for the characterization of post-translationally modified histones.
Mol. Cell Proteomics
PUBLISHED: 05-29-2013
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We present the first comprehensive capillary electrophoresis electrospray ionization mass spectrometry (CESI-MS) analysis of post-translational modifications derived from H1 and core histones. Using a capillary electrophoresis system equipped with a sheathless high-sensitivity porous sprayer and nano-liquid chromatography electrospray ionization mass spectrometry (nano-LC-ESI-MS) as two complementary techniques, we characterized H1 histones isolated from rat testis. Without any pre-separation of the perchloric acid extraction, a total of 70 different modified peptides, including 50 phosphopeptides, were identified in the rat linker histones H1.0, H1a-H1e, and H1t. Out of the 70 modified H1 histone peptides, 27 peptides could be identified with CESI-MS only, and 11 solely with LC-ESI-MS. Immobilized metal-affinity chromatography enrichment prior to MS analysis yielded a total of 55 phosphopeptides; 22 of these peptides could be identified only by CESI-MS, and 19 only by LC-ESI-MS, showing the complementarity of the two techniques. We mapped 42 H1 modification sites, including 31 phosphorylation sites, of which 8 were novel sites. For the analysis of core histones, we chose a different strategy. In a first step, the sulfuric-acid-extracted core histones were pre-separated using reverse-phase high-performance liquid chromatography. Individual rat testis core histone fractions obtained in this way were digested and analyzed via bottom-up CESI-MS. This approach yielded the identification of 42 different modification sites including acetylation (lysine and N(?)-terminal); mono-, di-, and trimethylation; and phosphorylation. When we applied CESI-MS for the analysis of intact core histone subtypes from butyrate-treated mouse tumor cells, we were able to rapidly detect their degree of modification, and we found this method very useful for the separation of isobaric trimethyl and acetyl modifications. Taken together, our results highlight the need for additional techniques for the comprehensive analysis of post-translational modifications. CESI-MS is a promising new proteomics tool as demonstrated by this, the first comprehensive analysis of histone modifications, using rat testis as an example.
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Stability of the endosomal scaffold protein LAMTOR3 depends on heterodimer assembly and proteasomal degradation.
J. Biol. Chem.
PUBLISHED: 05-07-2013
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LAMTOR3 (MP1) and LAMTOR2 (p14) form a heterodimer as part of the larger Ragulator complex that is required for MAPK and mTOR1 signaling from late endosomes/lysosomes. Here, we show that loss of LAMTOR2 (p14) results in an unstable cytosolic monomeric pool of LAMTOR3 (MP1). Monomeric cytoplasmic LAMTOR3 is rapidly degraded in a proteasome-dependent but lysosome-independent manner. Mutational analyses indicated that the turnover of the protein is dependent on ubiquitination of several lysine residues. Similarly, other Ragulator subunits, LAMTOR1 (p18), LAMTOR4 (c7orf59), and LAMTOR5 (HBXIP), are degraded as well upon the loss of LAMTOR2. Thus the assembly of the Ragulator complex is monitored by cellular quality control systems, most likely to prevent aberrant signaling at the convergence of mTOR and MAPK caused by a defective Ragulator complex.
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MALDI-MS tissue imaging identification of biliverdin reductase B overexpression in prostate cancer.
J Proteomics
PUBLISHED: 03-18-2013
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New biomarkers are needed to improve the specificity of prostate cancer detection and characterisation of individual tumors. In a proteomics profiling approach using MALDI-MS tissue imaging on frozen tissue sections, we identified discriminating masses. Imaging analysis of cancer, non-malignant benign epithelium and stromal areas of 15 prostatectomy specimens in a test and 10 in a validation set identified characteristic m/z peaks for each tissue type, e.g. m/z 10775 for benign epithelial, m/z 6284 and m/z 6657.5 for cancer and m/z 4965 for stromal tissue. A 10-fold cross-validation analysis showed highest discriminatory ability to separate tissue types for m/z 6284 and m/z 6657.5, both overexpressed in cancer, and a multicomponent mass peak cluster at m/z 10775-10797.4 overexpressed in benign epithelial tissue. ROC AUC values for these three masses ranged from 0.85 to 0.95 in the discrimination of malignant and non-malignant tissue. To identify the underlying proteins, prostate whole tissue extract was separated by nano-HPLC and subjected to MALDI TOF/TOF analysis. Proteins in fractions containing discriminatory m/z masses were identified by MS/MS analysis and candidate marker proteins subsequently validated by immunohistochemistry (IHC). Biliverdin reductase B (BLVRB) turned out to be overexpressed in PCa tissue.
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Optimization and evaluation of a sheathless capillary electrophoresis-electrospray ionization mass spectrometry platform for peptide analysis: comparison to liquid chromatography-electrospray ionization mass spectrometry.
Anal. Chem.
PUBLISHED: 09-01-2011
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In this study we have evaluated the suitability of a sheathless capillary electrophoresis-electrospray ionization mass spectrometry (CE-ESI-MS) interface with a porous tip as the nanospray emitter for use in peptide analysis. A positively charged capillary coating and 0.1% formic acid as background electrolyte were used for separation upstream from mass spectrometry characterization. The influence of the distance between emitter tip and MS inlet, ESI voltage applied, and of the electroosmotic flow (EOF) on electrospray performance and efficiency of the system was investigated in detail. Under optimized conditions, less than 30 amol of a model peptide (angiotensin I) was required for a detection in the base peak electropherogram and positive identification via tandem MS. Three different cationic capillary coatings were investigated for stability, resolution, and EOF and were found to enable reproducible separations by CE-ESI-MS. After optimizing MS settings, the effectiveness of the CE-ESI-MS method developed was compared with a state-of-the-art nano-liquid chromatography (LC)-ESI-MS method by analyzing Arg-C-digested rat testis linker histones with both systems. With comparable amounts of sample applied, the number of identified peptides increased by more than 60% when using CE-ESI-MS. We found that low molecular mass peptides (below 1400 Da) were preferentially identified by CE-ESI-MS, since this group of peptides poorly interacted with the reversed-phase material in the nano-LC system. Finally, total analysis time in LC-ESI-MS for three runs including equilibration was nearly 4 times longer than that of CE-ESI-MS: 246 versus 66 min.
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Influence of biological assay conditions on stability assessment of radiometal-labelled peptides exemplified using a 177Lu-DOTA-minigastrin derivative.
Nucl. Med. Biol.
PUBLISHED: 02-15-2011
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Lack of correlation between in vitro and in vivo stability is a general problem for the development of radiopeptides especially in the case of minigastrin derivatives for therapeutic applications. In this study, we compared the influence of experimental conditions on radiopeptide stability results in vitro using a model Minigastrin (MG) analogue labelled with Lu-177. Additionally, we attempted to characterize the main serum enzymatic cleavage sites by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) analysis.
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Polymorphism in vitamin D-binding protein as a genetic risk factor in the pathogenesis of endometriosis.
J. Clin. Endocrinol. Metab.
PUBLISHED: 10-27-2010
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Previous studies have implicated a deficiency in the inflammatory response in women who develop endometriosis. The specific immunological deficits have not been completely elucidated.
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Virus analysis using electromigration techniques.
Electrophoresis
PUBLISHED: 08-08-2009
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We discuss the progress during the last 4 years in the analysis of viruses by electrophoresis in capillaries and microfluidic devices. The paper is the continuation of a review published in this journal in 2005 [Kremser, L., Blaas, D., Kenndler, E., Electrophoresis 2004, 25, 2282-2291]. Eighteen papers on the topic have appeared since; the majority deals with zone electrophoresis and three reports are on IEF. These methods have been applied to human rhinoviruses, poliovirus Semliki Forest virus, norovirus-like particles, and the two bacteriophages MS2 and T5. A main finding was that addition of detergents and salts to the BGEs are essential for the robustness of the CE analysis. Analyte detection was usually via UV absorbance but there are some examples where the viruses were rendered fluorescent via modification of the capsid proteins with reactive dyes and/or by non-covalent attachment of intercalating fluorescent compounds to the nucleic acids making up the viral genome. Interestingly, some viruses are permeable to small molecular mass components; this allows fluorescent dyes to diffuse into the intact virus where they attach to the nucleic acid. Release of a viral genome upon heating was also monitored by using similar methodologies. Interactions of viruses and subviral particles with antibodies, receptors, and receptor-decorated liposomes were investigated with CE methods, all by using a non-equilibrium approach (i.e. co-incubation of the components prior to CE separation). Viruses are multivalent (i.e. possess many identical surface-exposed patches) and most of them are composed of defined numbers of identical subunits. The high resolution of CE has been most remarkably demonstrated by the separation of stoichiometric complexes between virus and a distinct number of soluble recombinant receptors and revealed their concentration-dependent distribution.
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N-chlorotaurine, a long-lived oxidant produced by human leukocytes, inactivates Shiga toxin of enterohemorrhagic Escherichia coli.
PLoS ONE
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N-chlorotaurine (NCT), the main representative of long-lived oxidants produced by granulocytes and monocytes, is known to exert broad-spectrum microbicidal activity. Here we show that NCT directly inactivates Shiga toxin 2 (Stx2), used as a model toxin secreted by enterohemorrhagic Escherichia coli (EHEC). Bacterial growth and Stx2 production were both inhibited by 2 mM NCT. The cytotoxic effect of Stx2 on Vero cells was removed by ?5.5 mM NCT. Confocal microscopy and FACS analyses showed that the binding of Stx2 to human kidney glomerular endothelial cells was inhibited, and no NCT-treated Stx2 entered the cytosol. Mass spectrometry displayed oxidation of thio groups and aromatic amino acids of Stx2 by NCT. Therefore, long-lived oxidants may act as powerful tools of innate immunity against soluble virulence factors of pathogens. Moreover, inactivation of virulence factors may contribute to therapeutic success of NCT and novel analogs, which are in development as topical antiinfectives.
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