Raman spectroscopic study on the structure of water in aqueous solution of [formula omitted]-amino acids

Abstract

The structure and hydrogen bonding of water in an aqueous solution of various α , ω -amino acids were analyzed using the contours of the O H stretching in the polarized Raman spectra. From the relative intensity of the collective band ( C value) corresponding to a long-range coupling of the O H stretching in the aqueous amino acid solutions, the number of hydrogen bonds disrupted due to the presence of one amino acid molecule ( N corr value) was evaluated. The N corr value for glycine was slightly positive, whereas with an increase in the number of methylene groups between ammonium and carboxylate groups, the N corr value gradually increased. These results suggest that the species with proximal anionic and cationic groups do not disturb the hydrogen-bonded network structure of water significantly, probably due to the counteraction of the electrostatic hydration effect attributable to the anionic and cationic groups.