We took some of our crude peptide and used ammonium iodide in TFA to reduce
methionine sulfoxide. Then we dissolved in 20% acetic acid and ran down a
sephadex column to clean the peptide up. However, the peptide seems to
have been partially acylated (extra masses of 42 and new HPLC peaks). Has
anyone else seen this problem? I'm wondering if the acetic acid might be
reduced to an aldehyde by the excess iodide or somehow an anhydride forms?
I would have thought the use of acetic acid would be quite safe. Thanks
for any comments.
Colin Barrow
University of Melbourne
Australia