Coherent X-ray and laser spectroscopy measurements of diffusion in concentrated alpha-crystallin solutions

Advisors: Laurence B. Lurio; Carol Thompson.Committee members: Omar Chmaissem.The mammalian eye lens is composed of a concentrated solution of water soluble proteins called crystallins. Alpha-crystallin, the most abundant protein found in the lens, plays a crucial role in maintaining lens transparency and lens accommodation. However, alpha-crystallins along with other ocular proteins suffer from irreversible processes such as oxidation. One cause of oxidation is radiation-induced radical formation which alters the inter-molecular interactions, thereby degrading the normal function of ocular proteins.;The main goal of this thesis is to quantify molecular scale dynamics of concentrated solutions of alpha-crystallins using coherent X-rays and visible laser light. I believe a detailed analysis of the dynamics pertaining to alpha-crystallin will provide the foundation to understand molecular scale mechanisms that lead to conditions like cataract and presbyopia. I explore the dynamics of concentrated alpha-crystallin solutions by measuring diffusive motion over a range of length scales using Dynamic light scattering (DLS) and X-ray photon correlation spectroscopy (XPCS). To a certain extent, the dynamical properties of crystallins obtained in this manner are consistent with established theories in colloidal physics. However, there are some deviations, which I will address in this thesis.;In terms of X-ray data, I employed a new, efficient photon correlation technique to obtain the best possible signal, furthermore this technique is embedded in a stand-alone software program that has the ability to provide real time results, quickly and efficiently with the help of high performance computing resources available at Northern Illinois University (NIU). The technique has potential to be used by the coherent X-ray spectroscopy community in the future. In addition, by using X-ray scattering data, I probe potential modifications and or damage effects on alpha-crystallins due to radiation exposure. The damage analysis methodology described in this thesis will be an important check for future XPCS experiments on biological systems. During the entire research project two X-ray detectors were used to collect data. Both are based on a quasi column-parallel, charge-coupled device (CCD) architecture which had identical back-end electronics and control circuits, but differed mainly in terms of their size and data readout mode. In this thesis, I will also focus on characterizing and optimizing the aforementioned X-ray detectors for XPCS measurements on alpha-crystallins.Ph.D. (Doctor of Philosophy