Len,
just to add to that, what you observe as an +32 adduct of Trp is the oxidation
of tryptophane. Nevertheless, the +32 can be due to the oxidation of
tryptophane, to the oxidation of two methionine residues to methionine sulfoxide
each or to the full oxidation of one methionine residue to methionine-sulfone.
We have observed all scenarios numerous times digestion mixtures anlyzed by LC-
MS. I can give you a reference if you want me to.
Kristine
Kristine Swiderek
Assoc. Research Director, Biological Structure
ZymoGenetics, Inc.
1201 Eastlake Ave. E
Seattle, WA 98102
Phone: (206)515-4901
Fax: (206)442-6608
e-mail: swiderek@zgi.com
_______________________________________________________________________________
Subject: Re: Prevent of Oxidizingof Met.
From: Len Packman <lcp2@mole.bio.cam.ac.uk> at smtpgate-zgi
Date: 3/4/99 8:56
Sook Shin
How did you determine the mass of the peptide? We have observed that
Trp-containing peptides analysed by madli in alphacyano-4-hydroxycinnamic
acid can often give +32amu peaks. If the sample is reanalysed by using
sinapinic acid, the +32 peak disappears, confirmed by esms. A cautionary
note before assuming that there is really an oxidation present.
Len
*********************************************************************
Dr Len C. Packman
Assistant Director of Research
Protein and Nucleic Acid Chemistry Facility
Department of Biochemistry
University of Cambridge
80 Tennis Court Road
Old Addenbrookes Site
Cambridge, CB2 1GA, UK
Tel: +44 (1223) 333639
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e-mail: lcp2@mole.bio.cam.ac.uk
Visit my WWW page at http://www.bio.cam.ac.uk/proj/adr/PNAC/pnac.html
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From: Len Packman <lcp2@mole.bio.cam.ac.uk>
Subject: Re: Prevent of Oxidizingof Met.
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