IR and FTIR studies of proton polarizability and proton transfer with hydrogen bonds and hydrogen-bonded systems-importance of these effects for mechanisms in biology

Abstract

Homoconjugated B + H … B ↭ B … H+B as well as heteroconjugated AH … B ↭ -A … H+B bonds show proton polarizability due to fluctuation and shifts of the proton within these hydrogen bonds. These proton polarizabilities are about two orders of magnitude larger than polarizabilities of electron systems. The catalytic mechanism of serine proteinases which is based on a shift of the positive charge in a hydrogen bond with large proton polarizability is discussed. Particularly large proton polarizabilities caused by collective proton motion in hydrogen-bonded chains are observed. This result is obtained with poly-α-amino acid + dihydrogen phosphate systems and studied with intramolecular hydrogen-bonded chains. A theoretical treatment has been performed with the formic acid-water-formate and the formic acid-water-water-formate systems. It is shown that the proton pathway in the L550 intermediate of bacteriorhodopsin as well as the pathway in the F0 subunit of the ATP synthase are hydrogen-bonded systems with large proton polarizability.