4-vinylpyridine [ 4-ethenylpyridine,4-vinylpyridine hydrobromide,4-vinylpyridine hydrochloride,4-vinylpyridine ion (1-),4-vinylpyridine nitrate,4-vinylpyridine perchlorate,4-vinylpyridine sulfate (1:1),HI of 4-vinylpyridine ] reagent for blocking cysteine function in proteins; RN given refers to parent cpd