Fractal analysis of aggregates in heat-induced BSA gels

The fractal structure of the aggregates in heat-induced bovine serum albumin (BSA) gels was analyzed. Three kinds of BSA gels were prepared by heating BSA solutions: (i) pH 5.1 without CaCl2; (ii) pH 7.0 with 30 mmol/dm(3) CaCl2; and (iii) pH 7.0 with 5 mmol/dm(3) CaCl2. First, from the concentration dependences of elasticity for the gels, using the theory of Shih et al. on colloidal gels, the fractal dimensions were evaluated. These BSA gels showed weak-link behavior according to the theory of Shih et al.: the limit of linearity gamma(o) increased with increasing BSA concentration. Second, from the images of the aggregates in the gels obtained with confocal laser scanning microscopy, the fractal dimensions of heat-induced BSA gels were evaluated using the box counting method. The fractal dimensions D-f for the three gels evaluated from rheological measurement were close to those evaluated from image analysis, the value of D-f for the gels being similar to 2.6-2.8. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.