Re: Cyanogen Bromide cleavage

Henry Keutmann (keutmann@helix.mgh.harvard.edu)
Tue, 17 Aug 1999 13:27:59 -0400

Ulf,
Thanks for your comments....indeed, we did find cleavage in high
yield at a Trp-Met bond after cyanogen bromide cleavage of a
peroxide-oxidized protein. We'd done the cleavage to verify complete
oxidation and, till your message, we were baffled by this finding. Looking
hard, we found traces of cleavage at some other Trps linked to residues
other than methoinine. But we hadn't added iodide or other halides so we
wouldn't expect those to go to any great degree.
From the responses, it doesn't seem like there are examples of CNBr
cleavage at any other residue, however.
Henry Keutmann.

>Henry K and other ABRF'ers,
>Yes, you may find cleavage C-term of Trp. A few years ago it was displayed
>on a poster at MPSA (Snowbird, I believe) that when making CNBr cleavage in
>the presence of low conc of Na- or -K-iodine clevage at Trp definitively
>occurs. It might be so that the, in standard CNBr cleavage, sometimes seen
>Trp cut is due to contamination with those salts?? If you prohibit Met
>cleavage by e g reversible oxidation, you have a nice Trp cleaving agent!
>I vagely remember that this was discussed in this forum a few years ago...
> Regards /Ulf
>Ulf Hellman, Ph. D.
>Prof.
>Ludwig Institute for Cancer Research
>Box 595
>SE-751 24 Uppsala
>Sweden
>
>Phone +46 18 160423
>Fax +46 18 160420
>E-mail "ulf.hellman@licr.uu.se"
>alt. "cykeldoktorn@hotmail.com"