John Keyte John.Keyte at
Thu Sep 21 09:51:47 EST 1995

Just a brief thought about doing tryp cleavages: I've just been doing a
little myself and after consulting a few texts decided not to use
BNPS-skatole as
(i) the cleavages are by no means quantitative
(ii) I didn't want my lab to smell like a toilet
In the end I went for O-iodosobenzoic acid from Pierce chemicals. The
cleavage was still not as complete as, say, CNBr but it did work. there is
always a problem with tryp cleaving reagents also cutting at tyrosines
also. However, even adding free tyrosine did not stop tyr in the protein I
looked at becoming modified though they did not actually cleave. I have
used CNBr a lot with few real problems, but if you use TFA instead of
formic acid be prepared to get acid cleavages (esp. at asp-pro bonds) in
addition to met cleavages. also, oxidised met does not cleave with CNBr.
Hope this has been some use.K. Bailey

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