Single Position Peptide Bond Modifications

Single Position Peptide Bond Modifications 7.9.1 Thioamide Pseudopeptides... 

Analysis of sulfotyrosine peptides and locahzation of sulfotyrosine positions in the presence of multiple potential sulfation sites can be a challenging task, in particular, if multiple sulfotyrosines are present in a single peptide chain, which is the case with most N-terminal chemokine receptor peptides. While mass spectrometry analysis of protein phosphorylation on a proteomics scale is well established, this is not the case for protein tyrosine sulfation. Due to the inherent lability of the sulfotyrosine sulfoester bond, partial or complete loss of the sulfotyrosine modification is generally observed as a neutral loss of SO3 (AMr = -80 Da) under standard mass spectrometry conditions. In particular, irrespective of the desorption/ionization method employed, positive... 

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