Standard molar entropy

About: Standard molar entropy is a research topic. Over the lifetime, 1586 publications have been published within this topic receiving 29886 citations.

Binding of diclofenac sodium with bovine serum albumin at different temperatures, pH and ionic strengths.

Abstract: The study was designed to examine the binding of diclofenac sodium with bovine serum albumin (BSA) at different temperatures (20 degrees, 30 degrees and 40 degrees C), pH (6.4, 7.4 and 8.4) and ionic strengths (micro = 0.1, 0.2 and 0.3) by means of equilibrium dialysis method. The concentration of diclofenac sodium was maintained at wider range from 15 to 900 micromole/l and BSA concentration was maintained at 61.5 micromole/l. The data obtained were interpreted by nonlinear regression method using Graphpad prism software. The analysis showed that the interaction between diclofenac sodium with BSA results in two-site saturable binding. A decrease in association constant was observed with increasing temperature. The average standard free energy change (deltaGdegrees) value was -7.07 (site I) and -4.2 (site II) Kcal/mol. The standard enthalpy change (deltaHdegrees) and the standard entropy change (deltaSdegrees) were -7.8 Kcal/mole, -2.35 cal/mole (site I) and -7.4 Kcal/mole, -10.5 cal/mole (site II), respectively. The negative enthalpy change suggested the binding between diclofenac sodium and the binding sites of BSA were spontaneous and exothermic. The negative value of deltaHdegrees and deltaSdegrees indicated hydrogen bonding and van der Waal's force was the major mechanism for diclofenac sodium and BSA interaction. Increase in pH and ionic strength also caused decrease in association constant of diclofenac sodium and BSA binding.

Determination of proton affinity from the kinetics of proton transfer reactions. III. The measurement of the equilibrium constant at various temperatures

Abstract: The flowing afterglow measurements of the equilibrium constants for selected proton transfer reactions have been extended to temperatures other than room temperature in order to completely specify the thermodynamics of such reactions. The van't Hoff analysis of the data for the reaction CO2H++CH4⇄ CH5++CO2 results in a value for the standard enthalpy change, ΔH° (196 to 553°K), of −0.064±0.004 eV and for the standard entropy change, ΔS° (196 to 553°K), of +1.4±0.6 e.u. Studies of the reaction N2OH++CO⇄ COH++N2O led to a value of −0.151±0.009 eV for ΔH° (277 to 505°K) and a value of −1.8±1.1 e.u. for ΔS° (277 to 505°K). ΔH° is a direct measure of the difference between the proton affinities of CO2 and CH4 in the former case and of N2O and CO in the latter. The measured values for ΔS° yield differences in the standard entropies of the protonated species: S°298(CH5+)−S°298(CO2H+)= −5.2± 0.6 e.u and S°298(COH+)−S°298(N2OH+)= −7.1± 1.1 e.u. Reference to calculated values for the standard entropy of CH5+ an...

Hydrogen peroxide: the low temperature heat capacity of the solid and the third law entropy

Abstract: The heat capacity of crystalline hydrogen peroxide between 12° K. and the melting point has been determined with a low temperature adiabatic calorimeter. The heat of fusion was also measured and fo...