Investigations of Various Interactions of Protein model compounds in Lithium and Sodium Salt of Nitrates Using Volumetric and Model Approach

Abstract

Apparent molar volumes, V2,? of glycine, DL-?-alanine, DL-?-amino-n-butyric acid, L-valine and L-leucine in water and in (0.25, 0.5, 0.75, 1.0, 1.5, 2.0) mol?kg-1 aqueous sodium nitrate solutions and in aqueous li-thium nitrate solutions at 298.15K have been determined at various temperatures (288.15, 298.15, 308.15 and 318.15) K from density measurements. The standard partial molar volumes at infinite dilution, V20 obtained from V2,?, have been used to calculate the corresponding volumes of transfer, ?tV0 from water to aqueous sodium nitrate solutions. The hydration number, nH, side chain contributions and volumetric interaction coefficients of these amino acids have also been calculated. The ?tV0 values for the studied amino acids are positive, and these values increase with an increase in the concentration of NaNO3 as well as with temperature. These parameters obtained from the volumetric study have been used to understand various mixing effects due to the interactions between amino acids and LiNO3, NaNO3 in aqueous solutions. Comparison of partial molar volumes of lithium nitrate and sodium nitrate will indicate a very interesting observations that Li+ being very small in size will show very high polarization in water and according to cosphere model, lithium ion will occupy very large water molecule because of high hydration; therefore the partial molar volumes of lithium nitrate is lesser as compared to sodium nitrate which is opposite as we supposed.