Hydration structure around the methylene group of glycine molecule

Neutron diffraction measurements have been carried out on aqueous 4 mol% glycine solutions. The H/D isotopic substitution technique was applied to both methylene-hydrogen (H-M) and water-hydrogen (H-W) atoms in order to obtain information concerning the hydration structure around the methylene group within the glycine molecule. Structural parameters for the first hydration shell of the methylene-hydrogen atoms were determined as r(H-M O-w) = 2.64(1) A and r(H-M...H-w) = 2.87(1) A from the least squares fitting analysis of the observed first-order difference function, (0H)Delta(H)(Q), and the partial structure factor, alpha(HM)H(cx)(Q) respectively. The first hydration shell of the methylene group involves ca. 2 water molecules per one glycine molecule.