Dynamics of proteins: Light scattering study of dilute and dense colloidal suspensions of eye lens homogenates

TL;DR

This study uses dynamic light scattering to analyze protein suspensions in bovine eye lenses, revealing how temperature and concentration affect protein diffusion and interactions, which are crucial for understanding lens transparency and cataract formation.

Contribution

It provides new insights into protein diffusion behaviors in lens-like suspensions under physiological conditions, linking experimental data to potential mechanisms of lens opacification.

Findings

Two scattering entities identified as alpha-crystallins and aggregates

Self-diffusion coefficients are temperature insensitive

Collective diffusion coefficient depends strongly on temperature

Abstract

We report a dynamic light scattering study on protein suspensions of bovine lens homogenates at conditions (pH and ionic strength) similar to the physiological ones. Light scattering data were collected at two temperatures, 20 oC and 37 oC, over a wide range of concentrations from the very dilute limit up to the dense regime approaching to the physiological lens concentration. A comparison with experimental data from intact bovine lenses was advanced revealing differences between dispersions and lenses at similar concentrations. In the dilute regime two scattering entities were detected and identified with the long-time, self-diffusion modes of alpha-crystallins and their aggregates, which naturally exist in lens nucleus. Self-diffusion coefficients are temperature insensitive, whereas the collective diffusion coefficient depends strongly on temperature revealing a reduction of the net repulsive interparticle forces with lowering temperature. While there are no rigorous theoretical approaches on particle diffusion properties for multi-component, non-ideal hard-sphere, polydispersed systems, as the suspensions studied here, a discussion of the volume fraction dependence of the long-time, self-diffusion coefficient in the context of existing theoretical approaches was undertaken. This study is purported to provide some insight into the complex light scattering pattern of intact lenses and the interactions between the constituent proteins that are responsible for lens transparency. This would lead to understand basic mechanisms of specific protein interactions that lead to lens opacification (cataract) under pathological conditions.