ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
(L-His)n- dihydrogen phosphate systems are studied by ir spectroscopy in the presence of various cations and as a function of the degree of hydration. Ir continua indicate that (I) OH … N ⇌ O-…H+N (IIR) hydrogen bonds are formed and that these bonds show high proton polarizability, which increases from the Li+ to the K+ system. In the K+-system, His-Pi-Pi chains are formed, showing particularly high proton polarizability due to collective proton motion within both hydrogen bonds. The OH N ⇌ O-…H-N equilibria are determined from ir bands. With the Li+ system, 55% of the protons are present at the histidine residues; this percentage is smaller with the Na+ system (41%), and amounts to only 32% with the K+ system. With the increasing degree of hydration the removal of the degeneracy of νas-PO2-3 vanishes, indicating loosening of the cations from the phosphates. Nevertheless, the hydrogen bond acceptor O atom becomes more negative; a shift of the equilibrium to the right is observed in the OH… N ⇌ O-…H+N bond. This is explained by the strong interaction of the dipole of the hydrogen bonds with the water molecules. All these results show that protons can be shifted easily in these hydrogen bonds due to their high proton polarizability. The transfer equilibria can be controlled easily by local electrical fields. In addition, these results may be of significance when phosphates interact with proteins.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.360260111
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