Dear Suzanne,
PTH-Met-sulfoxide elutes between PTH-Q and PTH-T on our 120A. A easy way to
check where it elutes in your system is: buy Met-sulfoxide from Sigma,
couple 1ug on a Arylamin disc from Millipore, wash with S1 and S2 and
sequence it using your standard protocol. In our 477 approximately 70% of
the Met-sulfoxide gets reduced to Met (by UV). Interestingly a peptide with
Met-sulfoxide in cycle 8 still showed 30% PTH-Met-sulfoxid in the analyzer.
The oxidized form of the peptide can normally easy be separated from the
non-oxidized by RP-HPLC. They elute earlier and are best spotted by LC-MS
(+ 16Da). In one case I could even separate two forms of a 15600Da protein
only differing by a oxidation of one Met!
With best regards Daniel
Dr. Daniel Hess
Friedrich Miescher Institut
Postfach 2543
CH-4002 Basel
Tel.: 061 697 85 44 or 061 697 68 68 FAX: 061 697 3976
e-mail: dhess@fmi.ch