ISSN:
1432-1017
Keywords:
Conformation
;
Polarizable hydrogen bonds
;
IR spectroscopy
;
Proteins
;
Proton transfer
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Physics
Notes:
Abstract The OH ⋯ N ⇌ O− ⋯ H+N hydrogen bonds formed between tyrosine and lysine, and between glutamic acid and lysine residues are studied by infrared spectroscopy considering the following systems: (l-lys)n + phenol, copoly (l-lys, l-tyr)n, (l-lys)n + (l-tyr)n and (l-lys)n + (l-glu)n. The phenol-lysine hydrogen bonds are largely symmetrical in the average if the pKa of the protonated lysine is 2.2 units larger than that of the phenols. In the case of the hydrogen bonds between tyrosine and lysine residues in copoly (l-lys, l-tyr)n and (l-lys)n + (l-tyr)n, the weight of the proton limiting structure OH ⋯ N is 80–90%, and that of the polar O− ⋯ H+N structure 10–20%. Double minimum proton potentials occur but the proton is preferentially present at the tyrosine residues. In the (l-lys)n + (l-glu)n system, the protons are present at the lysine residues. Thus, these hydrogen bonds have very large dipole moments (about 10 D). With the lysine-phenole hydrogen bonds, hydration shifts the proton transfer equilibrium a little in favour of the polar proton limiting structure O− ⋯ H+N. These hydrogen bonds are broken to a large extent, however, when only about 3 water molecules are present per lysine residue. When less water is present, as in the copoly (l-lys, l-tyr)n and (l-lys)n + (l-tyr)n systems, these hydrogen bonds are, however, formed quantitatively. Thus — as discussed in this paper — the tyrosine-lysine hydrogen bonds can participate in proton conducting hydrogen bonded systems — as, for instance, present in bacteriorhodopsin — performing the proton transport through hydrophobic regions of biological membranes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00537294
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