DYNAMIC LIGHT-SCATTERING OF AQUEOUS-SOLUTIONS OF LINEAR AGGREGATES INDUCED BY THERMAL-DENATURATION OF OVALBUMIN

Dynamic light scattering measurements were performed on dilute aqueous solutions of native ovalbumin (OA) and on those of linear OA aggregates induced by thermal denaturation at low ionic strength and neutral pH. The weight-average molecular weight M(W) of four aggregates tested ranged from 1,700,000 to 5,500,000. The translational diffusion coefficient D0 of native OA at infinite dilution was estimated as 8.70 X 10(-7) cm2/s, which gave 56.0 angstrom as the diameter of the rigid spherical particle. The intensity autocorrelation function of linear OA polymers was analyzed with the cumulant method to obtain the first cumulant GAMMA(e). The dependence of GAMMA(e) on the scattering vector q at very low polymer concentration was found intermediate between those of a flexible chain and a rigid rod. The translational diffusion coefficient D(tr) [= (GAMMA(e)/q2)q-->0] was in proportion to M(W)-0.55, and the magnitude was in good agreement with a value calculated from the wormlike cylinder model with values of three parameters determined in an earlier study, M(L) = 1600 angstrom-1, d = 120 angstrom, and Q = 230 angstrom, where M(L), d, and Q are the molecular weight per unit length, diameter, and persistence length, respectively. Based on these results, a new model, to be called as the dimer model, was proposed to interpret the formation mechanism of linear OA polymers induced by thermal denaturation.