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Cysteine-containing Peptides (cysteine-containing + peptide)
Selected AbstractsSynthesis and use of a pseudo-cysteine for native chemical ligationJOURNAL OF PEPTIDE SCIENCE, Issue 4 2003David A. Alves Abstract The process of native chemical ligation (NCL) is well described in the literature. An N -terminal cysteine-containing peptide reacts with a C -terminal thioester-containing peptide to yield a native amide bond after transesterification and acyl transfer. An N -terminal cysteine is required as both the N -terminal amino function and the sidechain thiol participate in the ligation reaction. In certain circumstances it is desirable, or even imperative, that the N -terminal region of a peptidic reaction partner remain unmodified, for instance for the retention of biological activity after ligation. This work discusses the synthesis of a pseudo- N -terminal cysteine building block for incorporation into peptides using standard methods of solid phase synthesis. Upon deprotection, this building block affords a de factoN -terminal cysteine positioned on an amino acid sidechain, which is capable of undergoing native chemical ligation with a thioester. The syntheses of several peptides and structures containing this motif are detailed, their reactions discussed, and further applications of this technology proposed. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd. [source] Design and synthesis of a solid-phase fluorescent mass tagJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2005Yang Shi Abstract In this study, we demonstrate the design of a new solid-phase fluorescent mass tag (FMT) that contains the following features: (1) the FMT is synthesized using Fmoc chemistry which is simple, rapid, and cost-effective; (2) lysine is used as a uniformly labeled amino acid (using stable isotopes) to allow 8 Da difference between "heavy" and "light" tags; (3) a fluorescent molecule is coupled to the isotope tag that allows a tagged peptide to be detected by online fluorescence; and (4) an iodoacetyl reactive group provides cysteine reactivity. Using MALDI-TOF MS and HPLC, we show that the FMT reagent can be used to label standard cysteine-containing peptides as well as cysteine-containing peptides from a BSA tryptic digest. [source] Desulfurization of cysteine-containing peptides resulting from sample preparation for protein characterization by mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 3 2010Zhouxi Wang In this study, we have examined two cysteine modifications resulting from sample preparation for protein characterization by mass spectrometry (MS): (1) a previously observed conversion of cysteine into dehydroalanine, now found in the case of disulfide mapping and (2) a novel modification corresponding to conversion of cysteine into alanine. Using model peptides, the conversion of cysteine into dehydroalanine via , -elimination of a disulfide bond was seen to result from the conditions of typical tryptic digestion (37°C, pH 7.0,9.0) without disulfide reduction and alkylation. Furthermore, the surprising conversion of cysteine into alanine was shown to occur by heating cysteine-containing peptides in the presence of a phosphine (tris(2-carboxyethyl)phosphine hydrochloride (TCEP)). The formation of alanine from cysteine, investigated by performing experiments in H2O or D2O, suggested a radical-based desulfurization mechanism unrelated to , -elimination. Importantly, an understanding of the mechanism and conditions favorable for cysteine desulfurization provides insight for the establishment of improved sample preparation procedures of protein analysis. Copyright © 2010 John Wiley & Sons, Ltd. [source] Cysteine-reactive covalent capture tags for enrichment of cysteine-containing peptidesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 21 2009Priscille Giron Considering the tremendous complexity and the wide dynamic range of protein samples from biological origin and their proteolytic peptide mixtures, proteomics largely requires simplification strategies. One common approach to reduce sample complexity is to target a particular amino acid in proteins or peptides, such as cysteine (Cys), with chemical tags in order to reduce the analysis to a subset of the whole proteome. The present work describes the synthesis and the use of two new cysteinyl tags, so-called cysteine-reactive covalent capture tags (C3T), for the isolation of Cys-containing peptides. These bifunctional molecules were specifically designed to react with cysteines through iodoacetyl and acryloyl moieties and permit efficient selection of the tagged peptides. To do so, a thioproline was chosen as the isolating group to form, after a deprotection/activation step, a thiazolidine with an aldehyde resin by the covalent capture (CC) method. The applicability of the enrichment strategy was demonstrated on small synthetic peptides as well as on peptides derived from digested proteins. Mass spectrometric (MS) analysis and tandem mass spectrometric (MS/MS) sequencing confirmed the efficient and straightforward selection of the cysteine-containing peptides. The combination of C3T and CC methods provides an effective alternative to reduce sample complexity and access low abundance proteins. Copyright © 2009 John Wiley & Sons, Ltd. [source] Screening for disulfide-rich peptides in biological sources by carboxyamidomethylation in combination with differential matrix-assisted laser desorption/ionization time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2001Susanne Neitz Peptides with biological functions often contain disulfide bridges connecting two cysteine residues. In an attempt to screen biological fluids for peptides containing cysteine residues, we have developed a sensitive and specific method to label cysteines selectively and detect the resulting molecular mass shift by differential mass spectrometry. First, reduction of disulfide bridges and carboxyamidomethylation of free thiols is adjusted to quantitatively achieve cysteine alkylation for complex peptide extracts. In a second step, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) before and after chemical derivatization is performed, followed by differential analysis to determine shifted peaks; shifted peaks belong to cysteine-containing peptides, other peaks remain unchanged. The number of cysteines can then be determined by the resulting molecular mass shift. Free, reduced cysteines are shifted by 57,u, two oxidized cysteines involved in disulfide bridges (cystine) result in a shift to higher mass per disulfide bridge of 116,u. Disulfide bridges connecting different amino acid chains like insulin break up during reduction. In this case, two peaks with lower molecular masses result from a single one in the unmodified sample. With this technique, we were able to identify cysteine-containing peptides and short fragments of proteins present in human blood filtrate. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||