Faculty Publications
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Item Molecular interactions in glycylglycine-mncl2 aqueous solutions at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) k(2009) Santosh, M.S.; Bhat, D.K.; Bhat, A.S.The viscosities, ultrasonic velocities, densities, and refractive indices of glycylglycine and MnCl2in water have been studied at different temperatures and concentrations. Excess thermodynamic parameters such as adiabatic compressibility (?ad), apparent molar volume (?V), apparent molar compressibility (?K),intermolecular free length (Lf), specific acoustic impedance (Z), relative association (RA), and salvation number (Sn) have been calculated. The variations in apparent molar volume were confirmed by Scaled particle theory, and the changes in apparent molar compressibilities were interpreted using the Kirkwood model. The variations in apparent molar volumes were fitted with Masson's equation. The viscosity data have been fitted using the Jones-Dole empirical equation. The molecular relaxation of MnCl2and glycylglycine in water gives an idea about solute-solute interactions. The interactions also suggest the formation of H-bonding in the system. The tructure forming tendency of the solute has also been indicated by the solvation number. Copyright& copy; 2009 American Chemical Society.Item Physico-chemical, acoustic and excess properties of glycylglycine-MnCl2 in aqueous ethanol mixtures at different temperatures(2010) Santosh, M.S.; Bhatt, A.S.; Bhat, D.K.Volumetric, acoustic, refractometric, excess and deviation properties of glycylglycine-MnCl2 in aqueous ethanol mixtures have been reported at T = (288.15 to 318.15) K. Redlich-Kister equation was used to fit the derivate properties. The experimental data of the constituent binaries were analyzed to discuss the nature and strengths of intermolecular interactions. The interdependence of Lf and u has been evolved from Eyring and Kincaid model. The variations in specific acoustic impedance revealed that hydrogen bonding was predominant in the studied binary mixtures. Solvation number indicated structure-breaking tendency of the solute and weakening of local solvent structure. © 2010 Elsevier B.V. All rights reserved.Item Volumetric, refractometric, and excess properties of glycylglycine in aqueous FeCl2 solution at temperatures T = (288.15 to 318.15) K(2010) Santosh, M.S.; Bhat, D.K.; Bhatt, A.S.Densities and refractive indices have been measured for glycylglycine in aqueous FeCl2 solution as a function of concentration at T = (288.15 to 318.15) K. The apparent molar volumes and partial molar volumes were obtained from these density data. The limited partial molar expansivities have been calculated from the temperature dependence of the partial molar volume. The molar refractions were calculated from the experimental refractive index values for the studied mixture. The excess volumes and molar refractions were also calculated. The results are discussed in terms of molecular interactions. © 2010 American Chemical Society.Item Excess molar volumes, viscosity deviations and isentropic compressibility changes in glycylglycine-NiCl2 aqueous ethanol mixtures(2010) Santosh, M.S.; Bhat, D.K.The densities, viscosities and ultrasonic velocities for glycylglycine-NiCl2 in aqueous ethanol mixtures have been studied in the temperature range 288.15-318.15K. The excess molar volumes, viscosity deviations and changes in isentropic compressibility for the binary mixtures have been calculated and discussed in terms of hydrogen bonding and structure-breaking effect. The computed results are fitted to the Redlich-Kister polynomial. The results clearly indicate that there is a strong association in the mixtures studied. © 2010 Elsevier B.V.Item Refractive indices and isentropic compressibilities of glycylglycine- FeCl2 in aqueous ethanol mixtures(2010) Santosh, M.S.; Bhat, D.K.The density and refractive index studies have been carried out for glycylglycine-FeCl2 in aqueous ethanol mixtures at four different temperatures in the range T = (288.15 to 318.15) K. A comparative study of the refractive indices obtained experimentally and those calculated by means of Gladstone-Dale and Lorentz-Lorenz relation has been made. Among them, the Gladstone-Dale equation afforded similar values to those obtained experimentally. Isentropic compressibilities, -S, and excess molar isentropic compressibilities, KS,mE, were estimated using the Kirkwood model. Using the Redlich-Kister type equations, excess partial molar isentropic compressibilities, KS,iE, were also obtained. The observed negative values of KS,2E in the water-rich region are due to the structural disorderliness. As infinitely dilute water is hydrogen-bonded to ethanol and glycylglycine, the variation of strength of interaction is not sensed by KS,1E,?. © 2010 American Chemical Society.Item Acoustical and compressibility parameters of glycylglycine-FeCl3 in aqueous ethanol mixture at T = (293.15, 303.15, and 313.15) K(2010) Santosh, M.S.; Bhat, D.K.Ultrasonic velocity measurement is a reliable procedure that allows quick and easy determination of solvent concentrations in mixtures. This paper presents data of ultrasonic velocities and isentropic compressibilities of (glycylglcyine-FeCl3) in aqueous ethanol mixture at T = (293.15, 303.15, and 313.15) K. Various acoustical parameters were calculated, because of their importance in the study of specific molecular interactions. A less-compressible phase of the fluid and a closer packing of molecules is observed with changes in the intermolecular free length. Quantitative investigation suggests that the mixing of ethanol with an aqueous glycylglycine-FeCl3 solution causes the rupture of hydrogen bonds, with increasing S and Lf values (where the former represents the change in isentropic compressibility and the latter represents the intermolecular free length). Theoretically computed values of isentropic compressibility in the studied mixture using different models indicate the superiority of the very complex procedure. © 2010 American Chemical Society.Item Molecular dynamics investigation of dipeptide - Transition metal salts in aqueous solutions(American Chemical Society service@acs.org, 2010) Santosh, M.S.; Lyubartsev, A.; Mirzoev, A.; Bhat, D.K.Molecular dynamics (MD) simulations of glycylglycine dipeptide with transition metal ions (Mn2+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+) in aqueous solutions have been carried out to get an insight into the solvation structure, intermolecular interactions, and salt effects in these systems. The solvation structure and hydrogen bonding were described in terms of radial distribution function (RDF) and spatial distribution function (SDF). The dynamical properties of the solvation structure were also analyzed in terms of diffusion and residence times. The simulation results show the presence of a well-defined first hydration shell around the dipeptide, with water molecules forming hydrogen bonds to the polar groups of the dipeptide. This shell is, however, affected by the strong electric field of divalent metal ions, which at higher ion concentrations lead to the shift in the dipeptide-water RDFs. Higher salt concentrations lead also to increased residence times and slower diffusion rates. In general, smaller ions (Cu2+, Zn2+) demonstrate stronger binding to dipeptide than the larger ones (Fe2+, Mn 2+). Simulations do not show any stronger association of peptide molecules indicating their dissolution in water. The above results may be of potential interest to future researchers on these molecular interactions. © 2010 American Chemical Society.Item Excess and deviation properties of {(glycylglycine + ZnCl2) in aqueous methanol} mixtures(2011) Santosh, M.S.; Bhat, D.K.The excess molar volumes (VE), viscosity deviations (??), deviations in isentropic compressibility (?? S) and excess molar refractivity (?RmE) for {(glycylglycine + ZnCl2) in aqueous methanol} mixture have been calculated from the experimental values. The bridging water molecules bend the chains into stable open ring structures together with intermolecular hydrogen bonding and interstitial accommodation leading to negative VE values. The positive ?? values indicate a structure breaking effect of aqueous glycylglycine-ZnCl2 upon contact with methanol molecules. It is also noted that chelation of zinc to glycylglycinate is through carboxylic group and not the amino group. The negative ??S values suggest the formation of an open ring structure lowering the entropy of the solution. Due to weak interaction between solute and solvent, the molecular structure of individual molecule does not change significantly and leads to negative ?RmE values. Finally, the results have lead to a good understanding of the thermodynamics properties of the studied liquid mixture. © 2010 Elsevier Ltd. All rights reserved.Item Molecular interactions between glycylglycine and Mn(COOCH3) 2 in aqueous and aqueous ethanol mixtures(2011) Santosh, M.S.; Bhat, D.K.; Bhatt, A.S.This paper reports the variations of different physical and thermodynamic properties of a mixture of dipeptide-metal salt in aqueous solutions as well as in aqueous ethanol mixtures. Specifically, the apparent molar volumes and apparent molar compressibilities of glycylglycine and Mn(COOCH3) 2 have been determined at T = (288.15 to 318.15) K, and the resulting data have been used to estimate the limiting volume (?0 V) and compressibility (?0K). Their concentration variations are examined to study the effect due to solute-solute and solvent-solvent interactions. The resulting data have been used to interpret the volume and compressibility contributions of the components in terms of H-bonding and dipole-dipole interactions. It was found that these interactions in aqueous solutions were measurably distinct in some cases from those in alcohols. An unusual behavior in the refractive index values indicates a measure of the relative extent of the polar domains. © 2009 American Chemical Society.