hi to all,
I'm studying a protein having 3 cysteines. When I perform the reaction with IAM, I notice that the protein is being Carbamidomethylated on four residues. are there other residues in addition to cysteines subjected to carbamidomethylation?
Hi Antonio,
the short answer is yes. Take a look at these papers;
E. S. Boja and H. M. Fales. Overalkylation of a protein digest with iodoacetamide. Anal.Chem. 73 (15):3576-3582, 2001.
R. Kruger, C-W. Hung, M. Edelson-Averbukh, and W. D. Lehmann. Iodoacetamide-alkylated methionine can mimic neutral loss of phosphoric acid from phospopeptides as exemplified by nano-electrospray ionisation quadrupole time-of-flight parent ion scanning. Rapid Commun.Mass Spectrom 19 (12):1709-1716, 2005.
Michael L. Nielsen, Michiel Vermeulen, Tiziana Bonaldi, Jurgen Cox, Luis Moroder, and Matthias Mann. Iodoacetamide-induced artifact mimics ubiquitination in mass spectrometry. Nat Meth 5 (6):459-460, 2008.
There are bound to be others as well...
Peter
That is a definite yes. This is actually very common in methionine, and we observe that quite routinely when we are manually looking through glycopeptide MS/MS data. There are diagnostic patterns in the tandem MS, and you can observe them at a different elution time on a reversed phase column.
