Structurally symmetrical, easily polarizable hydrogen bonds between side chains in proteins and proton-conducting mechanisms. III
✍ Scribed by Wolfgang Kristof; Georg Zundel
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1980
- Tongue
- English
- Weight
- 839 KB
- Volume
- 19
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Republic of Germany synopsis (L-Cys),, (L-LYS),, and (L-G~u), were studied by ir spectroscopy in terms of their degree of deprotonation or protonation. It is shown that structurally symmetrical, easily polarizable SH-S-+ -S--HS, N+H-N =N.--H+N, and OH---0-* -0-HO hydrogen bonds are formed between the side chains. The different wave number distributions of the ir continua caused by these hydrogen bonds show that the barrier in the double-minimum proton potential decreases in the series of these hydrogen bonds. The stability of these hydrogen bonds against hydration increases in this series. The OH-0-+ -O.-HO bonds are not broken by small amounts of water. With (L-CYS), the formation of easily polarizable hydrogen bonds and a fl-structure-coil transition are strongly interdependent. As a result of this coupling effect, the fi-structure-coil transition becomes cooperative. With (L-G~u),, the formation of the polarizable hydrogen bonds and the observed conformational change are independent processes. The (L-Glu), conformation changes from a-helix to coil only if more than 80% of the residues are deprotonated. Finally, on the basis of the various types of easily polarizable hydrogen bonds, charge shifts in active centers of enzymes and the proton-conducting mechanism through hydrophobic regions of biological membranes are discussed.