Structural interactions of globular proteins—Bovine serum albumin, egg albumin, and lysozyme, in aqueous medium, elucidated with molar volumes, viscosities, energy functions, and IR spectra from 293.15 to 303.15 K

Densities (ρ), apparent molar volumes ( V ϕ ), viscosities (η), and IR spectra on 0.0010–0.0018% aqueous solutions of bovine serum albumin (BSA), egg albumin (E‐Alb), and lysozyme at an interval of 0.0004% and at temperatures from 293.15, 298.15, and 303.15 K have obtained. The free energy (Δ G ), entropy (Δ S ), and enthalpy (Δ H ) data with compositions and temperatures are calculated from the values of the flow velocity ( v f ) of viscous flow, which decrease with temperature. The densities decrease with concentrations and temperatures except BSA, and the V ϕ values slightly increase with concentrations for BSA and lysozyme, which depict structural reorientations and transition states of protein molecules with increase in viscosities and decrease in reduce viscosities. The reduce viscosities at 293.15 K for BSA, E‐Alb, and lysozyme are noted positive, and for BSA and lysozyme remain positive at 298.15 and 303.15 K, whereas for E‐Alb it is negative. Activation energies ( E *) for lysozyme remain almost constant, and are higher than those of the BSA and E‐Alb, respectively, also slightly higher E * values for the BSA than those of the E‐Alb at 293.15 and 298.15, and lower than of the E‐Alb at 303.15 K, are observed elucidating greater structural interactions for BSA at lower while weaker at temperatures. Stretching frequencies of amide (NHCO), NH, CO, and CH groups of proteins are noted from IR spectra with broader stretching frequencies for NH. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1420–1429, 2007