Dear Radhika,
I agree with Gregory and Andy and can only add the relevant references I
have posted last millenium in connection with observations similar to
yours.
I hope you'll find them useful.
<<I'm almost sure that your peptide is OK.
It looks like you have resolved conformers formed by methylated peptide
bonds -C(O)-N(Me)-. Slow interconversion (on NMR, HPLC and CZE "time
scales") of cis/trans isomers of -X-Pro- and, in
particular(!), -Pro-Pro- containing peptides is well documented
(J.Chromatogr., 1989, 478, 121-9; Anal.Chem. 1995, 67(19), 3464-75 +
refs cited therein).
You may verify this by changing temperature during HPLC. At lower
temperatures baseline separation of the conformers could be achieved,
while peak coalescence is to be expected at 40-50 deg.C.>>
Good luck.
Igor
------------------------------------------------
Igor L. Rodionov
Laboratory of Peptide Chemistry
Branch of Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry
Pushchino, Moscow Region
142292, Russian Federation
rodionov@fibkh.serpukhov.su
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