Effect of temperature on viscosity properties of some alpha-amino acids inaqueous urea solutions

Viscosities for solutions of glycine, DL-alpha-alanine, DL-alpha-amino-n-bu tyric acid, DL-valine, DL-leucine and L-serine in 5 mol kg(-1) aqueous urea have been determined at 278.15, 288.15, 298.15 and 308.15 K. The viscosity B-coefficients for the amino acids in the aqueous urea solution have been calculated at different temperatures. The effect of temperature on the B-co efficients is discussed on the basis of the Feakins equation. The contribut ion of solute to the activation parameters (Delta mu(2)(0 not equal), Delta H-2(0 not equal), Delta S-2(0 not equal)) for viscous flow of the solution have been calculated, together with the Gibbs energy, enthalpy and entropy of transfer for the amino acids from the ground-state solvent to the hypot hetical viscous transition state solvent. The contributions of the charged end group (NH3+, COO-) and CH2 groups of the amino acids to B-coefficient a nd Delta mu(2)(0 not equal) have been also estimated using the linear corre lations between B-coefficient or Delta mu(2)(0 not equal) and the number of carbon atoms in the alkyl chains of the amino acids. All the activation pa rameters are discussed in terms of the solute-solvent interactions in the g round and transition states. (C) 2000 Elsevier Science B.V. All rights rese rved.