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
Science Avenue 6
Pushchino, Moscow Region
142292, Russian Federation
E-mail: rodionov@fibkh.serpukhov.su
Fax: (0967)-79-05-27
Phones: (0967) 73 54 42; private: (0967) 73 58 26
http://www.fibkh.serpukhov.su/