Re: 4-vinylpyridine, iodoacetic acid
Ioannis Papayannopoulos (iap@tp.net)
Wed, 12 Aug 1998 20:41:13 -0400
Jim,
Some years ago I had a situation where alkylation of a protein with
4-vinylpyridine (after disulfide reduction with DTT and with no other
alkylating agent used) resulted in the generation of one proteolytic
peptide which, in addition to alkylation of the Cys residue present in its
sequence, has some other amino acid alkylated with 4-vinylpyridine as well
(104 u higher in mass). The ratio of the two products (mono and
dialkylated) was, if I rememeber correctly, 50:1 to 100:1, as determined by
their respective MS relative ion abundances. I don't think we ever
identified the second amino acid to which 4-vinylpyridine had been,
unexpectedly, attached; however, the only amino acids which had side chains
that could, conceivably, be modified were Glu, Ser, and Lys at the
C-terminus (all other amino acids had "non-reactive" side chains). Your
sequence also contains Ser and Lys; my guess is that Ser may be the amino
acid modified, by analogy to Cys.
Ioannis Papayannopoulos
CytoMed, Inc.
Cambridge, MA