The structure of biopolymer-containing microemulsions: A light-scattering study at the optical match point

Abstract

In this study, we focus on the size and structure perturbations induced in the reverse micellar system upon solubilization of the enzyme α-chymotrypsin by using light-scattering techniques. The knowledge of the geometrical parameters is very important in order to develop a good theoretical model of the driving forces responsible for polymer and biopolymer solubilization in microemulsions. Since the size difference between the empty reverse micelles and the average size measured in the biopolymer-containing solution is often very small, the size distribution changes induced by the presence of biopolymers cannot be determined unambiguously by normal light-scattering experiments.

However, we can overcome this problem by suppressing the scattering contributions from the empty reversed micelles close to the so-called optical match point of the microemulsion droplets. Light-scattering experiments at the optical match point thus provide a very sensitive method to quantitatively test the currently existing theoretical models for protein solubilization in microemulsions. Using the size distributions predicted by these models, we can calculate both the total scattering intensity as well as the z-average diffusion coefficient unambiguously from the known dielectric constants of the components following established procedures.