Partial molar volumes and expansibilities of some amino acids in water at 35°C

Abstract

Partial molar volumes of ten amino acids, <em>dl</em>-alanine, <em>I</em>-arginine, glycine, <em>I</em>-histidine, <em>I</em>-isoleucine, <em>l</em>-Iysine-HCI, <em>l</em>-methionine, <em>I</em>-proline, <em>I-</em>serine, and <em>dl</em> -threonine, in water, have been calculated from density measurements made at 35^oC. Amino acid-water interactions are interpreted from partial molar volume, V^o, data with particular reference to structural features of solute molecules, such as hydrogen bonding, side group interactions, etc. Comparison between present and previous data (at 25°C) shows that V<img src='http://www.niscair.res.in/jinfo/equation131.gif' border=0> values are higher by 1-3 cm³ mol^-1 than the respective V<img src='http://www.niscair.res.in/jinfo/equation130.gif' border=0> data. Hydration volumes are estimated using different estimates of intrinsic volumes. Isobaric expansibilities, E^o, are also calculated which indicate correlation between E^o and size, and between E^o and hydrophobicity of solute molecules.