Molecular conformation of poly-S-carboxytmethyl-L-cysteine in aqueous solutions

✍ Scribed by Shoichi Ikeda

• Publisher: Wiley (John Wiley & Sons)
• Year: 1967
• Tongue: English
• Weight: 695 KB
• Volume: 5
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1967.360050405

✦ Synopsis

J a p a n

Synopsis

Poly-S-carboxyniethyl-~cysteine has been prepared by debeiizylation of poly-Srarbobenzoxymethyl-bcysteine with hydrogen bromide in acetic acid. By the infrared spectroscopic method the polymer is found to be in the extended p-conformation with a n antiparallel arrangement of polypeptide chains in solid film, if it has been iegenerated from dimethyl siilfoxide solution. Aqueous solutions of the polymer have been investigated by measwements of optical rotatory dispersion and viscosity. I-arioris properties hharply change around pH 5 a t different ionic strengths. By combining these with infrared studies in D20 solutions, it has been shown that the polymer exists in the random coil conformation a t higher ionization but associates into the intermolecnlar &conformation a t lower ionization. At the lowest pH attainable in solution, the p-form is partly converted into the random coil as the temperature is raised. The rotatory dispersion of the polymer is described by the Moffitt equation. While the random coil form has a large negative uo value and a zero bo value, the 0-form is characterized by a positive a0 valne and a negative b~ value, -130".