Effects of Hg(ClO4)2, HgCl2, and AgClO4 on the Conformations of Poly(S-carboxymethyl-l-cysteine) and Poly[S-(2-carboxyethyl)-l-cysteine] in Solution

Abstract

Abstract The effects of Hg(ClO4)2, HgCl2, and AgClO4 on the conformations of fully neutralized poly(S-carboxymethyl-l-cysteine) and poly[S-(2-carboxyethyl)-l-cysteine] in the absence of supporting electrolytes were examined by circular dichroism (CD) spectra. The induction of the β-form was suggested by the addition of Hg(ClO4)2 and AgClO4, while it could not be concluded in the case of HgCl2. Spectroscopic evidence for the coordination of metals with the two polypeptides was provided in the case of Hg(ClO4)2 and HgCl2 by the appearance of a new CD band around 250–260 nm as well as the distortion of the polymer CD spectra in the region of 200–230 nm, while it was not obtained in the case of AgClO4. The decrease of pH observed on addition of the three metal compounds also suggested the conformational change. Extraordinary lowering of pH and enhanced solubility were observed on addition of HgCl2.