Phase boundaries and liquid structure of concentrated eye lens protein mixtures

Project Summary Cataract disease, the leading cause of blindness worldwide, is the end result of increased scattering of light within the human ocular lens. The proposed research continues to establish the multi-component phase diagram of concentrated, aqueous eye lens crystallin protein mixtures, together with its statistical-thermodynamic molecular basis. A combined approach employing x- ray scattering, nuclear magnetic resonance, static and quasielastic light scattering, statistical thermodynamic modeling, computer simulation, and neutron scattering will be used (1) to test predictions of molecularly-detailed models of gamma crystallin interactions that seek to quantify angle-dependent potentials of mean force between lens gamma crystallins, (2) by combining top-down and bottom-up approaches, to study and define how distinct lens beta crystallin subtypes combine to form the quaternary beta crystallin structures observed upon isolation from lens cytoplasm, (3) to further study and refine relationships between molecular features, free energy, light scattering, and liquid structure in mixtures of two major crystallin classes, as foundations for systematically studying mixtures that contain three crystallin classes, (4) to study the thermodynamics, liquid structure, and phase diagram of controlled, concentrated aqueous mixtures of the three major classes of mammalian lens crystallins. Each step will involve the training of undergraduate researchers in both biochemistry and physics, and a physics doctoral student will also participate. Each step is an essential part of providing a sound molecular understanding of the light scattering, phase diagram, and dynamics of concentrated solutions and mixtures of gamma, alpha, and beta crystallin, and as such bears on the molecular origins of cataract.