Solution Properties of Synthetic Polypeptides. XIII. Dimensions of Interrupted Helices of Poly(γ-benzyl L-glutamate)

Abstract

The helix–coil transition of poly(γ-benzyl L-glutamate) in dichloroacetic acid containing 8.3-wt% cyclohexanol was studied by light-scattering and optical rotation measurements. Data for the mean-square radii of gyration ‹S2› were analyzed by the method of Teramoto et al., with the aid of the transition parameters estimated from the optical rotation data, yielding 1.53±0.1 Å for the pitch per monomeric residue in helical sections. This value is in excellent agreement with that of 1.5 Å expected for the α-helix, and confirms the recent result of Okita et al., for poly-[N5-(3-hydroxy-propyl) L-glutamine]. Light-scattering measurements were also made with solutions of a helicogenic solvent, dimethylformamide (DMF). The values of the pitch calculated directly from ‹S2› data in DMF were smaller than 1.5 Å and showed a trend to decrease slightly with increasing molecular weight, being in accordance with data of previous workers. This trend was successfully interpreted in terms of the interrupted helix model when the experimental values of the transition parameters for the helicogenic solvents was used.

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Norisuye, T., Teramoto, A. & Fujita, H. Solution Properties of Synthetic Polypeptides. XIII. Dimensions of Interrupted Helices of Poly(γ-benzyl L-glutamate). Polym J 4, 323–331 (1973). https://doi.org/10.1295/polymj.4.323

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Keywords

  • Helix–Coil Transition
  • Light Scattering
  • Interrupted Helix
  • Poly(γ-benzyl L-glutamate)
  • Mean-Square Radius of Gyration
  • Flexibility of Polypeptides in Helicogenic Solvents

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