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Subject: RE: Peptide??
Date: Thu, 24 Feb 2000 09:23:56 -0500
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IMHO:
You don't say exactly what the sequence is; but possibly an S is C-terminal
beyond sequencing? Is it really S or actually T? The pioneer does not
authenticate the sequence synthesized and operator error remains a high
probability.
Possibly D/E switches could also account for 14Da; but with MW higher than
expected, not the cause of this one.
Also, check your resin. If using pre-loaded, G/A switch accounts for this
(Also beyond the reach of N-terminal sequence).
To get at the C-terminus MS/MS could help.
Without M/C, oxidation seems to be unlikely.
These suggestions come from making exactly these types of mistakes.
David H. Singleton
Scientist
Pfizer Central Research
PO Box 8118-101
Eastern Point Road
Groton, CT 06340
-----Original Message-----
From: Terry Stoming [mailto:TSTOMING@MAIL.MCG.EDU]
Sent: Thursday, February 24, 2000 6:38 AM
To: Recipients of ABRF List
Subject: Peptide??
I ave recently synthesized a peptide with the following aa:
2G N and C terminal
2S
2R
1F
1T
1L
1E
MW 1109.2. The HPLC looks good. Synthesis was in the Perseptive Pioneer.
Coupling and deprotection look fine. Mass spec gives a good peak with a mw
of 1123.7. I sequenced the peptide on a procise (glass membrane). The
sequence died after 8aa which doesnt surprise me. The calls were 100% for
the first 8. What do I have? Why is the mw off by 15?
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