Abstract
High-resolution proton magnetic resonance spectra along with chemical shift and linewidth data are presented for the following polyamino acids throughout their β-coil transition regions in the mixtures of CDCl3 and dichloroacetic acid (DCA): poly-S-carbobenzexy-L-cysteine (PSCBLC), poly-O-acetyl-L-serine (2 molecular weights, POALS I and POALS II), and poly-O-benzyl-L-serine (POBLS) .
The changes in peak positions and linewidths in various solvent compositions were campared with the changes in a0 values obtained from the measurements of optical rotatory dispersion and Moffit-Yang's equation.
It was found that the NH and the α-CH peaks underwent upfield shift accompanied by broadening as the per cent DCA was decreased, and somewhat sharp transitions in the peak positions and the linewidths were observed, except the α-CH peak of POBLS, near the solvent compositions where the sharp transitions of a0 values occured. All other resonance peak positions remained nearly constant.
The broadening of the NH and the α-CH peaks occured in accordance with the increase in a0 vahles. The broadening of the peaks in the side chains were observed for PSCBLC and POBLS and not for POALS.
