Can you clarify at what pH you are running each of the two reactions?
Chris
>Dear ABRF collegues,
>
>Can anyone give me advice on activationg cys on a resin-bound peptide
>with SPyr? We have removed Mtt from the Cys with 1% TFA and added 5-10
>eq Dithiopyridine in 2-propanol/AcOH (2N), but get little change in
>absorption at 343nm (ext. coeff liberated SPyr = 7400 cm-1 M-1). We
>tested the reaction with an amount of free H-Cys-OH equivalent to that
>in the peptide and the color change was rapid and large. Is the reaction
>with resin bound peptide very slow?
>Also, what problems can we expect when emoving Acm from a second cys, or
>on cleaving the peptide (e.g from scavengers?).
>
>If we carry out the reaction on a free peptide, can we remove residual
>SPyr and dithiopyr without having to chromatograph?
>
>Thanks, Alex
>
>======================================================================
>Dr. Alessandro Tossi
>Antiinfective peptides group
>Dept. of Biochemistry, Biophysics and Macromolecular Chemistry
>University of Trieste
>Phone -- 39 40 6763673; Fax -- 39 40 6763691
>email: tossi@bbcm.univ.trieste.it
>http://www.bbcm.univ.trieste.it/~tossi
>=====================================================================
Christopher Halkides
Dept. of Chemistry, UNCW
601 S. College Road
Wilmington, NC 28403-3297