The optical rotatory properties of poly-γ-D-glutamic acid

✍ Scribed by D. I. Marlborough

• Publisher: Wiley (John Wiley & Sons)
• Year: 1973
• Tongue: English
• Weight: 400 KB
• Volume: 12
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1973.360120512

✦ Synopsis

Abstract

Measurement of the optical rotatory dispersion spectra of poly‐γ‐D‐glutamic acid (obtained from Bacillus anthracis) dawn to 200 nm wavelength reveal difference between the unionized and ionized froms. The profile of the unionized polyacid shows similarities to those obtained for α‐helical polypeptides, although with displaced frequencies of the respective maxima and minima. It is suggested that the relative position and magnitudes of the Cotton effect are consistent with a helical structure such as proposed by Rydon (J. Chem. Soc., 1964, 1328). The optical rotatory dispersion spectrum of the ionized from resembles those obtained from the β‐chain from of α‐L polypeptides. From model‐building studies an extended chain similer to the β‐from would seen the most reasonable structure for the ionized poly‐γ‐acid to adopt, since the charged groups in such a conformation would be at their maximal distances from each other. Such an ordered structure for a polymer is consistent with the hypotheses put forward in the recent literature that charged polypeptides adopt ordered rather than random‐coiled conformations.