ESI/Mass spec

Terry Stoming (TSTOMING@MAIL.MCG.EDU)
Mon, 30 Mar 1998 07:13:43 -0500

I have made a peptide with an N-terminal
serine. I left the Fmoc on and removed
the protecing groups and resin. The
LC/MS ( API-100 electrospray) shows a
peak (about 90% pure) with a molecular
ion showing the Fmoc on. I dissolved
the peptide ~40mg in 2ml DMF and added
500ul of piperidine. Shake for 5 minutes
and precipitate and wash with
t-butylmethyl ether. LC/MS now shows
four peaks:
1. about 35%-Correct mw wtih Fmoc
removed.
2. About 15% Mw +96 above the correct
molecular weight.
3. About 45% Mw +201 above the correct
molecular weight.
4. About 5% Mw +199 above the correct
molecular weight.

HELP!!