Interaction of (+)-catechin with the edge of the β sheet formed by poly-(S-carboxymethyl-L-cysteine)

Abstract

The interaction of (+)-catechin with poly-(S-carboxymethyl-L-cysteine) has been studied by circular dichroism spectroscopy. This polypeptide undergoes a pH-induced transition from a random coil to a β sheet under conditions where (+)-catechin is stable. The pH range over which the conformational transition occurs is broadened in the presence of (+)-catechin, but there is little effect on the pH at the midpoint of the transition. Qualitatively the same behaviour of the transition curves is observed in a theoretical model where the (+)-catechin interacts with, and stabilizes, the initial strand in the β sheet. This stabilization could result from the formation of a pair of hydrogen bonds between (+)-catechin and amide units in the initial strand.