Syn.Pep: Mass +517 ?????

mcada002@mc.duke.edu
Thu, 22 Jan 1998 15:58 -0500 (EST)

HELP!

I am having great difficulty with a synthetic peptide. I use FastMoc
chemistry on ABI 433A.

30 amino acids in length. Has one Asp-Gly site, one Asp-Tyr site, and
one Asp-Ser site. Composition = Lys(2), Asp(4), Ser(2), Leu(1),
Val(2), Tyr(2), Gly(6), Glu(3), Gln(2), Phe(2), Asn(1), Ile(1),
Thr(1), Arg(1). C-term. is CONH2. N-term is biotinylated.

The first sythesis gave no full length peptide. The mass of the
predominant peak agreed perfectly with chain cleavage at the Asp-Gly
site at cycle 13. Unlucky? I had synthesized with lengthy
deprotection thoughout, about 60 minutes each cycle. Weight gain not
recorded.

For the second synthesis I shortened deprotection by about 15 minutes.
However, this time I used the Fmoc-(FmocHmb)-Gly-OH derivative at the
Asp-Gly site. Synthesis was smooth enough as predicted by the
conductivity monitor. Weight gain was 81%. Usual cleavage with
Reagent K/2hrs. Analytical HPLC showed a dominant peak (approx. 60%)
with other smaller peaks nearby. Mass analysis says the dominant peak
is 3536. Expected mass is 3019.

Could this be incomplete deprotection of the Hmb-Gly? Does anyone
have experience with Hmb-Gly? What is the +517 mass? Can I recover
the desired peptide? Could something be going on between biotin and
the Hmb-Gly?

YOUR MISSION, SHOULD YOU AGREE TO ACCEPT, .........


Thanks for you thoughts!!

Millie McAdams
HHMI Biopolymer Facility @ DUMC
919 684-2652
919 684-5458 FAX
---------------------------------- Forwarded ----------------------------------
From: mcada002 at Perseus
Date: 1/22/98 10:34AM
To: abrf@aecom.yu.edu at Internet
Subject: Syn.Pep: Mass +517 ?????
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