Abstract
The interactions of poly(glutamic acid) with cobaltous ions (Co(II)) in aqueous solution were investigated by means of NMR in the temperature range from 0 to 70°C. It was found that as Co(II) is added the α-CH and the NH peaks shift to higher fields and the β-CH2 and γ-CH2 peaks shift to lower fields. It is considered that these shifts are paramagnetic shifts due to the paramagnetism of Co(II). Large shifts of the γ-CH2 peak indicate that Co(II) is coordinated with the carboxyl group. High-field shifts of the peak suggest that Co(II) is coordinated with the peptide NH. Paramagnetic shifts of the β-CH2 and γ-CH2 increased and those of the α-CH and NH decreased with increasing temperature. These results are interpreted in terms of changes in a chemical equilibrium between the Co(II)-free residues of PGA and the bonding ones. It is considered that the amount of Co(II) bonded to the carboxyl groups of PGA increases with increasing temperature. The temperature dependence of the shifts of β-CH2 and γ-CH2 suggests that the pseudocontact mechanism is also involved as well as the contact one.
Similar content being viewed by others
Log in or create a free account to read this content
Gain free access to this article, as well as selected content from this journal and more on nature.com
or
References
A. L. Jacobson, Biopolymers, 1, 269 (1963).
A. L. Jacobson, Biopolymers, 2, 237 (1964).
H. Takesada and H. Yamazaki, Biopolymers, 4, 713 (1965).
R. S. Milner and L. Pratt, Discuss. Faraday Soc., 34, 88 (1962).
Z. Luz and S. Meiboom, J. Chem. Phys., 40, 2686 (1964).
C. C. McDonald and W. D. Phillips, J. Am. Chem. Soc., 85, 3736 (1963).
Y. Kobayashi and H. Makino, Biochim. Biophys. Acta, 191, 738 (1969).
E. M. Bradbury and C. Robinson, Nature, 220, 1079 (1968).
J. L. Markly, D. H. Meadows, and O. Jardetzky, J. Mol. Biol., 27, 25 (1967).
J. A. Pople, W. G. Schneider, and H. J. Bernstein, “High Resolution Nuclear Magnetic Resonance.” McGraw-Hill Book Company, New York, N.Y., 1959, p 449.
N. Bloembergen, J. Chem. Phys., 27, 595 (1957).
H. M. McConnell and E. Robertson, J. Chem. Phys., 29, 1361 (1958).
B. Bleaney and D. J. E. Ingram, Proc. Roy. Soc., 208, 143 (1951).
G. N. La Mar, J. Chem. Phys., 41, 2992 (1964).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Iwaki, O., Hikichi, K., Kaneko, M. et al. An NMR Study of a Poly(glutamic acid) Metal Complex. Polym J 4, 623–627 (1973). https://doi.org/10.1295/polymj.4.623
Issue date:
DOI: https://doi.org/10.1295/polymj.4.623
