I am currently working in a lab and I am trying to purify a protein. We have a tryptophan followed by a his-tag (6 histidines) near the C-terminus. I was thinking of using BNPS-skatole to cleave the protein after the tryptophan but rumor has it that many tryptophan cleaving reagents have a habit of cutting Tyrosine as well, is this true? If so does O-iodosobenzoic acid do the same? Finally, does anyone have any advice at all? I’m going crazy, :-). Thanks
"many tryptophan cleaving reagents have a habit of cutting Tyrosine as well, is this true? "
Yes. However, this may or may not be a problem for your particular protein. The only way to find out for sure is to try it.
Get yourself a copy of “Chemical Modification of Proteins” by Means and Feeney. There are certainly more modern books on the subject but M&F has good coverage of most of the common tryptophan reagents.
The Pierce Chemical Co. catalog also has a lot of good information, books, and reagents.