Nmr study of poly(aspartic acid). I. α‐ and β‐Peptide bonds in poly(aspartic acid) prepared by thermal polycondensation

The structure of poly(aspartic acid) prepared by thermal polycondensation has been studied by means of nmr spectroscopy. The analysis of the 13 C‐nmr spectra of the polymer at various pH values and comparison with the spectrum of poly(α‐ L ‐aspartic acid) revealed that the polymer contained aspartic acid linked in α‐ and β‐peptide bonds. The mole fraction of the β‐peptide bonds has been found to be 0.8 ± 0.1. The significance of the results for the evolutionary theory of S. W. Fox is mentioned.