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  • GEL-FREE SAMPLE PREPARATION FOR THE NANOSCALE LC-MS/MS ANALYSIS AND IDENTIFICATION OF LOW-NANOGRAM PROTEIN SAMPLES 17763504

    Protein identification at the low nanogram level could in principle be obtained by most nanoscale LC-MS/MS systems. Nevertheless, the complex sample preparation procedures generally required in biological applications, and the consequent high risk of sample losses, very often hamper practical achievement of such low levels. In fact, the minimal amount of protein required for the identification from a gel band or spot, in general, largely exceeds the theoretical limit of identification reachable by nanoscale LC-MS/MS systems. A method for the identification of low levels of purified proteins, allowing limits of identification down to 1 ng when using standard bore, 75 microm id nanoscale LC-MS/MS systems is here reported. The method comprises an offline two-step sample cleanup, subsequent to protein digestion, which is designed to minimize sample losses, allows high flexibility in the choice of digestion conditions and delivers a highly purified peptide mixture even from "real world" digestion conditions, thus allowing the subsequent nanoscale LC-MS/MS analysis to be performed in automated, unattended operation for long series. The method can be applied to the characterization of low levels of affinity purified protei
    문서 타입:
    Reference
    카탈로그 번호:
    C5737
    제품명:
    ZipTip® Pipette Tips
  • Large-Scale Filter-Aided Sample Preparation Method for the Analysis of the Ubiquitinome. 28260372

    Protein ubiquitination regulates key cellular functions, including protein homeostasis and signal transduction. The digestion of ubiquitinated proteins with trypsin yields a glycine-glycine remnant bound to the modified lysine residue (K-ε-GG) that can be recognized by specific antibodies for immunoaffinity purification (IAP) and subsequent identification of ubiquitination sites by mass spectrometry. Previous ubiquitinome studies based on this strategy have consistently digested milligram amounts of protein as starting material using in-solution digestion protocols prior to K-ε-GG enrichment. Filter-aided sample preparation (FASP) surpasses in-solution protein digestion in cleavage efficiency, but its performance has thus far been shown for digestion of sample amounts on the order of micrograms. Because cleavage efficiency is pivotal in the generation of the K-ε-GG epitope recognized during IAP, here we developed a large-scale FASP method (LFASP) for digestion of milligram amounts of protein and evaluated its applicability to the study of the ubiquitinome. Our results demonstrate that LFASP-based tryptic digestion is efficient, robust, reproducible, and applicable to the study of the ubiquitinome. We benchmark our results with state-of-the-art ubiquitinome studies and show a ∼3-fold reduction in the proportion of miscleaved peptides with the method presented here. Beyond ubiquitinome analysis, LFASP overcomes the general limitation in sample capacity of standard FASP-based protocols and can therefore be used for a variety of applications that demand a large(r) amount of starting material.
    문서 타입:
    Reference
    카탈로그 번호:
    UFC901024
    제품명:
    Amicon® Ultra-15 Centrifugal Filter Unit
  • Homocysteine and other thiols determined in plasma by HPLC and thiol-specific postcolumn derivatization. 8353942

    We describe a versatile high-performance liquid-chromatographic method for determining homocysteine and other plasma sulfhydryls. Using three different procedures for preparation of plasma, we determined total, free (non-protein-bound), and reduced forms of homocysteine, cysteine, glutathione, cysteinylglycine, and gamma-glutamylcysteine in human plasma. Sample preparation involves disulfide reduction with dithiothreitol and protein precipitation with sulfosalicylic acid. The assay utilizes isocratic reversed-phase ion-pair liquid chromatography at pH 2.4, postcolumn derivatization with 4,4'-dithiodipyridine, and colorimetric detection at 324 nm. The intra-assay precision (CV) of the method for total homocysteine is 1.5%; the interassay precision over 2.5 months is 2.5%. The detection limit for homocysteine is < 50 nmol/L plasma.
    문서 타입:
    Reference
    카탈로그 번호:
    20-176
    제품명:
    100X GTPγS, 10mM
  • Cross-sample validation provides enhanced proteome coverage in rat vocal fold mucosa. 21423617

    The vocal fold mucosa is a biomechanically unique tissue comprised of a densely cellular epithelium, superficial to an extracellular matrix (ECM)-rich lamina propria. Such ECM-rich tissues are challenging to analyze using proteomic assays, primarily due to extensive crosslinking and glycosylation of the majority of high M(r) ECM proteins. In this study, we implemented an LC-MS/MS-based strategy to characterize the rat vocal fold mucosa proteome. Our sample preparation protocol successfully solubilized both proteins and certain high M(r) glycoconjugates and resulted in the identification of hundreds of mucosal proteins. A straightforward approach to the treatment of protein identifications attributed to single peptide hits allowed the retention of potentially important low abundance identifications (validated by a cross-sample match and de novo interpretation of relevant spectra) while still eliminating potentially spurious identifications (global single peptide hits with no cross-sample match). The resulting vocal fold mucosa proteome was characterized by a wide range of cellular and extracellular proteins spanning 12 functional categories.
    문서 타입:
    Reference
    카탈로그 번호:
    AB1954
    제품명:
    Anti-Fibronectin Antibody
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