Specificity of Endoproteinase Asp-N

[Shaun D. Black]

Howdy all,

      There are two ways to deal with cleavage at Cys residues, as best I
know:

      1. Modify with ethyleneimine.  This converts Cys into a derivative 
         that is isosteric with Lys, so trypsin will cleave such modified
         AE-Cys residues.

      2. Cyanylate Cys with Cyano-Thionitrobenzoate (CTNB).  Chemical
         peptide cleavage at the Cyano-Cys residues can be effected under
         alkaline conditions.

Methods in Enzymology has protocols for both of these procedures.  I hope
this helps a bit. 

Best regards,  Shaun

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  = Shaun D. Black, PhD   | Internet address:     shaun at jason.uthct.edu   =
  = Dept. of Biochemistry | University of Texas Health Center, at Tyler   =
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