I'd suspect your DG has become piperdine amide (+67) due to succinimide
dehydration (-18). You have an unresolvable mixture of products; <25%
desired material. You didn't mention how far in you successfully sequenced.
There is no exact, universal solution to this synthesis pitfall. HOBt in
the piperdine can help to alleviate it, but IMHO, isn't universal.
Perhaps BOC synthesis could help? If mutation is possible, it would make
life easier.
David H. Singleton
Scientist
Pfizer Central Research
Eastern Point Road
Groton, CT 06340
-----Original Message-----
From: lisa bibbs [mailto:bibbs@scripps.edu]
Sent: Friday, March 03, 2000 12:17 PM
To: Recipients of ABRF List
Subject: PepSyn: Trp peptide problem
I have the following peptide made with FMOC.
L W W L W W L W W K K C T W R G D G R C L K K (AMIDE)
It should have the mass
Mass
3134.790 (av.) 3132.625 (mono.)
When I cleave it I get mostly 3202 and 3116. We cleave with EDT,
water, thioanisole, anisole and TFA. We use Trp-Boc. Any
suggestions? I know it is full length cause I have sequenced it off
the bead.
Thanks,
Lisa
Lisa Bibbs, Ph.D.
10550 N. Torrey Pines Rd.
SP3
La Jolla, CA 92039
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