Partial molar volumes and adiabatic compressibilities of glycyl peptides at 25.degree.C

Abstract

Partial molar volumes (P) and adiabatic compressibilities (k") of di-, tri-, and tetraglycine have been calculated from high precision density and sound velocity measurements carried out at 25 "C. The contributions (V",o(gly) and K,"(gly)) of the glycyl unit, in a peptide of hypothetical infinite length, are estimated by four different techniques. Final values, obtained by averaging the concordant data, are 37.51 i 0.07 cm3 mol-' and (-8.50 k 0.01) X cm3 mol-' bar-' for V-"(gly) and kmo(gly), respectively. These values are required for use in a revised additivity scheme for calculating partial specific volumes and compressibilities of proteins. Contributions of the peptide group (-CONH-) to P and P are also estimated by comparing with data of o,w-amino acids. The values of i"(-CONH-) and R"(-CONH-) estimated in this way are 20.61 cm3 mol-' and -12.4 X cm3 mol-' bar-', respectively. Some plausible modes of peptide solvation also are discussed.

Thermodynamics of aqueous solutions of dodecyldimethylethylammonium bromide

“…In this way we can explain why apparent molar compressibilities of DEDAB and DTAB show the same trends vs m. In contrast, when a -CH 2 -is added to the hydrophobic chain, it is generally accepted that its group contribution to the molar compressibility is negative (−1.9 × 10 −4 cm 3 bar −1 mol −1 in Ref. [34], −1.6 × 10 −4 cm 3 bar −1 mol −1 in Ref. [21]) at infinite dilution.…”

“…The apparent molar volumes, V Φ and adiabatic compressibility, K s,Φ were calculated by means of the following equations [18][19][20][21]: where d is the density of the solution of molality m, M is the molecular weight of the surfactants, d 0 is the density of the solvent. β s,0 and β s are the coefficient of adiabatic compressibility of the solvent and of the solute, respectively.…”

Partial molar volume of mefenamic acid in alcohol at temperatures between T=293.15 and T=313.15 K

“…The density of various solutions was measured using an automated vibrating tube density meter (Anton Paar DMA 48), with an uncertainty of ±0.0001 g cm -3 , which was calibrated with air and doubly distilled water in the temperature range investigated. (1) Where ρ 0 = density of pure component 1 (solvent), ρ = density of solution of molality m of mefenamic acid having molar mass M 2 .…”

Physicochemical Properties of L-Alanine in Aqueous Silver Sulphate Solutions at (298.15, 308.15, and 318.15) K

“…Thermodynamic investigations of amino acids in aqueous solutions identified the significant hydration characteristics of the solutes [14][15][16][17] such as: (i) NH 3 + and COO − terminals in these solutes are hydrated in an electrostrictive manner and the intervening backbone is hydrated depending on its nature; (ii) electrostriction of the NH 3 + group is greater than that of the COO − group by a factor of 10; and (iii) the overlap of hydration co-spheres of terminal groups adjacent to the core results in a volume change. Thus, thermodynamic properties of amino acids in aqueous electrolyte solutions provide valuable information about solute-solvent and solute-solute interactions.…”