A. Matsushima, S. Yamazaki, K. Shibata
Jul 21, 1972
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Journal
Biochimica et biophysica acta
Abstract
tert-Butyl hypochlorite was examined as a reagent for modification of imino groups in aqueous solution and was applied to polypeptides and proteins, and the following facts were revealed. tert-Butyl hypochlorite possesses a moderate reactivity with imino groups at low temperature and between pH 3.9 and 8.1. About 80% of the imino groups in poly-l-glutamate are chlorinated at pH 7.9, while nearly none of the imino groups is modified at pH 4.1. In the case of poly-l-serine about 35% and 5% of the imino groups are reactive with tert-butyl hypochlorite in the absence and in the presence of 77% methanol, respectively. It was deduced from these results that almost all of the imino groups in random coil structures react with tert-butyl hypochlorite but those in α-helical structures or β-structures do not. About 60% of the total 51 imino groups in the native insulin molecule are reactive with tert-butyl hypochlorite, while most of them are reactive with tert-butyl hypochlorite after cleavage of the disulfide bonds by oxidation with performic acid.