In ASMS 97, Ron Beavis had an abstract for a method for cleaving after Trp
residues. On enquiry that year, he sent the method shown below. (Typically,
we haven't needed to try it until now!)
I can't find para-iodosobenozoic acid in Aldrich, only the 2- (ortho-) form.
I also do not understand the mechanism of action and the use of the term
1-iodoiodoxolin-3-one in Ron's subject line. I have been unable to contact
him at beavis@proteometrics.com to get clarification and no literature
searches have helped.
Can anyone help explain the reaction or get me in touch with Ron? Where can
one buy para-iodosobenozoic acid? Has anyone tried this reaction?
Len
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>Dissolve the following components in 2:1 water:acetonitrile, with 0.1% TFA
>
>0.5 millimolar para-iodosobenozoic acid
>0.1 millimolar sodium iodide
>
>Add that to your sample for a final sample concentration of approximately
>50 micromolar. Allow the reaction to continue for approximately 30 minutes
>at room temperature. Quench the reaction with DTT.
>
>Note: Methionines (+1 oxygen) and cysteines (+2 oxygens) are
>quantitatively oxidized by this procedure. Cysteines protected by acetate
>or acetimide groups do not seem to be oxidized, at least the rate is much
>slower that for methionines in the peptides we have examined. There is
>some iodination of aromatic groups, but for the reaction time indicated it
>is minimal.
>
>Note: The presence of excess halide ions (such as chloride) slows down the
>reaction. For best results, the protein sample should be as salt-free as
>possible.
>
>Ron Beavis
*********************************************************************
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
FAX: +44 (1223) 766002
e-mail: lcp2@mole.bio.cam.ac.uk
Visit my WWW page at http://www.bio.cam.ac.uk/proj/adr/PNAC/pnac.html