The conformational properties of poly(L‐p‐aminophenylalanine) have been investigated by potentiometric and circular dichroism (CD) techniques. It has been found that the polymer in the charge‐free state can assume two ordered conformations, depending upon temperature conditions. At room temperature the polymer assumes the right‐handed helical form by described Goodman and Peggion.1 At temperatures higher than 40°C a new ordered conformation has been found, whose slow rate of formation and ir absorption properties are typical of the β‐structure. The thermodynamic parameters relative to the coil‐β transition, determined by potentiometric titration techniques, revealed that the thermodynamic stability of the β‐structure is mainly due to enthalpic factors. The formation of this structure is unfavored on a kinetic basis. Copyright © 1976 John Wiley & Sons, Inc.
A potentiometric and CD investigation on the conformational properties of poly(L-p-aminophenylalanine) in aqueous solution.
PALUMBO, MANLIO;
1976
Abstract
The conformational properties of poly(L‐p‐aminophenylalanine) have been investigated by potentiometric and circular dichroism (CD) techniques. It has been found that the polymer in the charge‐free state can assume two ordered conformations, depending upon temperature conditions. At room temperature the polymer assumes the right‐handed helical form by described Goodman and Peggion.1 At temperatures higher than 40°C a new ordered conformation has been found, whose slow rate of formation and ir absorption properties are typical of the β‐structure. The thermodynamic parameters relative to the coil‐β transition, determined by potentiometric titration techniques, revealed that the thermodynamic stability of the β‐structure is mainly due to enthalpic factors. The formation of this structure is unfavored on a kinetic basis. Copyright © 1976 John Wiley & Sons, Inc.
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