Side-chain dynamics in poly(α-glutamate) and poly(γ-glutamate) aqueous solutions: a high-frequency dielectric investigation

Abstract

The side-chain dynamics in two polypeptides, poly(α-glutamate) and poly(γ-glutamate), in aqueous solutions were investigated by means of dielectric spectroscopic measurements carried out in the frequency range from 1 MHz to 1.8 GHz. The influence of the conformational transitions induced by pH was studied and the behaviour of the dielectric parameters of the observed dielectric dispersion (the dielectric increments and the relaxation times) as a function of the degree of ionization is discussed. These results suggest that the motion of the side-chain groups in both polymers is largely independent of the chain conformation, i.e., of the fraction of the helical content in the polymer chain. The findings indicate that the cooperative coupling mechanism between several repeat units in the coiled part of the chain, recently reported for similar polymers to take into account the observed dielectric relaxation, is invalid.

References

1. P. Doty, A. Wada, J. T. Yang and E. R. Blout, J. Polym. Sci., 1957, 23, 851.
2. D. Poland and H. Scheraga, Theory of Helix-Coil Transition in Biopolymers, Academic Press, New York, 1970.
3. S. Mashimo, in Dielectric Spectroscopy of Polymeric Materials, ed. J. P. Runt and J. J. Fitzgerald, American Chemical Society, Washington, DC, 1997, p. 201.
4. F. Bordi, C. Cametti and G. Paradossi, Biopolymers, 1996, 40, 485.
5. S. Takashima, Biopolymers, 1963, 1, 171.
6. M. Kumazaki and S. Sugai, J. Phys. Soc. Jpn., 1972, 32, 785.
7. H. Nakamura and A. Wada, Biopolymers, 1981, 20, 2567.
8. T. Aiuchi, N. Murai and S. Sugai, Biopolymers, 1974, 13, 1499.
9. S. Paoletti, A. Cesaro, C. Arce Samper and J. C. Benegas, Biophys. Chem., 1989, 34, 301.
10. G. Müller, F. van der Touw, S. Zwolle and M. Mandel, Biophys. Chem., 1974, 2, 242.
11. F. Bordi, C. Cametti and G. Paradossi, J. Phys. Chem., 1992, 96, 8194.
12. F. Bordi, C. Cametti and G. Paradossi, Macromolecules, 1992, 25, 4206.
13. F. Bordi, C. Cametti and G. Paradossi, J. Phys. Chem., 1992, 96, 913.
14. A. Wada, T. Tanaka and H. Kihara, Biopolymers, 1972, 11, 587.
15. G. Schwarz and J. Seeling, Biopolymers, 1969, 6, 1263.
16. J. B. Hasted, Aqueous Dielectrics, Chapman and Hall, London, 1973.
17. S. Takashima, Electrical Properties of Biopolymers and Membranes, Adam Hilger, Bristol, 1989.
18. F. van der Touw and M. Mandel, Biophys. Chem., 1974, 2, 218.
19. M. Mandel and T. Odijk, Annu. Rev. Phys. Chem., 1984, 35, 75.
20. C. Cametti and A. Di Biasio, Macromolecules, 1987, 20, 1579.
21. B. Hall, H. Wennerstroem and L. Piculell, J. Phys. Chem., 1984, 88, 2482.
22. S. Mashimo, T. Ota, N. Shinyashiki, S. Tanaka and S. Yagihawa, Macromolecules, 1989, 22, 1285.
23. F. Bordi, C. Cametti and G. Paradossi, Macromolecules, 1993, 26, 3363.
24. F. Yamaguchi, Y. Ogawa, M. Kikuchi, K. Yuasa and H. Moyai, Biosci. Biotechnol. Biochem., 1996, 60, 255.
25. S. Havriliak and S. Negami, Polymer, 1967, 8, 161.
26. E. H. Grant, R. J. Sheppard and G. P. South, Dielectric Behaviour of Biological Molecules in Solution, Clarendon Press, Oxford, 1978.
27. N. E. Hill, W. E. Vaughan, A. H. Price and M. Davies, Dielectric Properties and Molecular Behaviour, Van Nostrand Reinhold, New York, 1969.
28. A. Wada, Polyamino Acids, Polypeptides and Proteins, ed. M. A. Stahman, Wisconsin University Press, Madison, 1962.
29. K. Ito, A. Yagi, N. Ookubo and R. Hayakawa, Macromolecules, 1990, 23, 857.
30. A. V. Dobrynin, R. H. Colby and M. Rubinstein, Macromolecules, 1995, 28, 1859.
31. M. Rubinstein, R. H. Colby and A. V. Dobrynin, Phys. Rev. Lett., 1994, 73, 2776.
32. B. H. Zimm and J. K. Bragg, J. Phys. Chem., 1959, 31, 526.
33. B. H. Zimm and S. A. Rice, Biopolymers, 1960, 3, 391.
34. J. Applequist, J. Chem. Phys., 1963, 38, 934.
35. V. Munoz and L. Serrano, J. Mol. Biol., 1995, 244, 297.
36. V. Munoz and L. Serrano, Biopolymers, 1997, 41, 495.
37. R. L. Snipp, W. G. Miller and R. E. Nylund, J. Am. Chem. Soc., 1965, 87, 3547.
38. J. Rifkind and J. Applequist, J. Am. Chem. Soc., 1964, 86, 4207.
39. W. Zhang and S. Nilsson, Macromolecules, 1993, 26, 2866.