Two small suggestion: use Fmoc-Trp(boc)-OH, to prevent Trp side chain
problems
(refer to novabiochem catalog for Trp property). Before cleavage I
usually
degas the Mixture B bubbling N2, to eliminate O2, that should oxidize
Met. Met
oxidize to SO sulfoxide, not SO2, so you should have both the met
oxidized. You
can convert Oxidized met using
this protocol (ABI cleavage technique)
Dissolve the peptide in 10% HOAc to a final concentration between 1 to 5
mg/ml
Add N-(methyl)mercaptoacetamide (sigma M-8529)to have a 10%(w/v)
solution.
Incubate this solution under N2 at 37 C for 24/36 hour.
Monitor the reaction by HPLC. Your not oxidized peptide should have
longer RT.
If you are lucky I would expect the appearance of 3 peaks, and at longer
time
the accumulation in a unique peak. It stinks!!!!!!!
Maybe you can try on a little amount to rule out if this is your
problem.
If you have aTOF maldi with PSD you could sequence it and see the
oxidize met.
Good luck
-- Matteo Villain E-mail : villain@uab.edu Research Associate Phone : 205 934 3032 University of Alabama Fax : 205 934 1446 Birmingham 35294, USA