Quinoline, 2-ethenyl- (772-03-2)

   2-Vinylquinoline (CAS No.772-03-2), it also can be called 2-ethenylquinoline ; Quinoline, 2-ethenyl- ; Quinoline, 2-vinyl- ; 2-Vinyl-quinoline ; 2-Vinylquinoline 97% . It is dark orange-brown liquid. 2-Vinylquinoline is a reagent to determine protein sulfhydryl groups spectrophotometrically. 
   A reagent has been sought for the selective derivatization of protein sulfhydryl groups that will allow the spectrophotometric determination of the cysteine and cystine content of intact proteins. 2-Vinylquinoline(CAS No.772-03-2) appears to be that reagent. Protein sulfhydryl groups were reacted with 2-vinylquinoline to yield the protein-linked S-2-(2-quinolylethyl)- -cysteine (Qe-cysteine). After urea and other excess reagents were removed, the modified proteins were examined spectrophotometrically. The extinction coefficient (10,000) and absorption maximum (318 mμ) of the protein-linked vinylquinoline derivatives were identical to those of the model Qe-cysteine. Optimum conditions for the reaction require an equimolar concentration of 2-vinylquinoline to all sulfhydryls and a 4 hr reaction period. The total cysteine and cysteine contents of the proteins, when determined under these conditions, were in excellent agreement with standard literature values.
   Cystine content of legume seed proteins can be estimated by determination of cysteine with 2-vinylquinoline, and relation to protein content and activity of cysteine synthase.