Reanalysis of solute retention on immobilized human serum albumin using fractal geometry

Earlier experimental data for sucrose dependence of dansyl amino acid retention on immobilized human serum albumin (Peyrin E.; et al. Anal. Chem. 1998, 70, 2812) are reexamined within a fractal framework. A mathematical development based on the fractal geometry of Mandelbrot is proposed to provide a more realistic picture of the molecular association between the ligand and the site II cavity. The fractal dimension D of the cavity surface is calculated using the theoretical approach from previous data. Results show that the surface morphology of the cavity is strongly influenced by the surface tension effects of sucrose molecules, the salting-out agent leveling the surface irregularities. In addition, dansyl amino acid retention and thermodynamic parameter variations are discussed using this fractal concept of surface fluctuations.