Apparent molar heat capacities and volumes of some aqueous solutions of aliphatic amino acids at 288.15, 298.15, 313.15, and 328.15 K

Abstract

362 (1994).The thermodynamics of amino acid systems are key to the understanding of protein chemistry. We have found that many previous studies of the apparent molar volumes and heat capacities of aqueous solutions of amino acids were conducted at the standard temperature of 298.15 K. This does not allow for the fact that most biological processes occur at temperatures removed from this standard condition.In an attempt to address this imbalance we have measured densities and heat capacities for aqueous solutions of glycine, L-alanine, L-serine, and L-threonine at 288. 15, 298.15, 313.15, and 328.15 K using a Picker flow microcalorimeter. Apparent molar volumes and heat capacities, and the associated standard state partial molar properties have been calculated. Constant pressure variations of revised Helgeson, Kirkham, and Flowers equations have been fitted to calculated standard state volumes and heat capacities over the temperature range 288.15 to 328.15 K. These equations may be used to estimate standard state volumes and heat capacities, and hence equilibrium constants, for aqueous amino acid systems at higher temperatures.

Calorimetric investigations of aqueous amino acid and dipeptide systems from 288. 15 to 328. 15 K

“…The weights used in these calculations were calculated as the reciprocals of the squares of the uncertainties in the apparent molar volumes and heat capacities (1,17). Calculated uncertainties are contained in parentheses in Tables 1-6.…”

“…chemical properties of aqueous amino acid systems that we are constructing (1)(2)(3). This data base provides the framework on which we have constructed group additivity analyses that allow for the estimation of standard state volume and heat capacity data for aqueous amino acid and peptide systems in the temperature range 288.15-328.15 K. More specifically, the data reported in this paper allow for the calculation of the temperature dependences of peptide group contributions to structural components of standard state volumes and heat capacities.…”

Partial molar volumes of some amino acids and a peptide in water, DMSO, NaCl, and DMSO/NaCl aqueous solutions

“…In an aqueous solution, a DMSO molecule preferentially combines with two water molecules and forms a composite molecule as follows (13) (CH 3 ) 2 S = O OH 2 H O H Kinetic data from nuclear magnetic resonance and infrared techniques have shown that the interaction due to hydrogen bonding between DMSO and H 2 O is stronger than that between H 2 O molecules. Because of the more positive charge on the sulfur atom of the DMSO molecule, it has a strong polar interaction.…”

“…Because of the structural complexities of proteins and the non-feasibility of direct thermodynamic studies, amino acids and oligopeptides are often used as model compounds since they are the fundamental components of proteins. (1)(2)(3) The partial molar volume is a characteristic parameter showing the interaction between molecules in solution. Most of the previous studies on amino acids and peptides have been restricted to water at a specified temperature (often at T = 298.15 K).…”

Photoacoustic studies on two new organic NLO materials: L‐threonine and L‐prolinium tartrate

“…for LT and LPT, respectively [12,13]. Thermal effusivity (e) is the ability to exchange heat with the environment by the material and is given as [14]:…”