X-ray photon correlation spectroscopy experiments of protein dynamics at molecular length scales - potentials and limitations

Protein dynamics play an essential role in the functionality of biomolecules, and their behavior within dense environments presents a fascinating and complex field of study. Various factors, such as macromolecular crowding agents, have an impact on the dynamics of proteins in crowded conditions. Protein dysregulation in crowded cellular environments is associated with pathological conditions such as neurodegenerative diseases and blindness. The investigation of protein dynamics in solution plays a key role in various disciplines, including biophysics and pharmaceuticals, as it provides insights into essential aspects of protein behavior, aggregation, and interactions. However, due to the experimental challenges related to measuring dynamics on a molecular-length scale, the dynamics are still mostly unknown.
X-ray photon correlation spectroscopy (XPCS) has been considered an excellent technique for investigating protein dynamics at molecular-length scales. This thesis provides a comprehensive description of a current study that explores the potential and limitations related to the use of XPCS to determine the dynamics of protein solutions (specifically IgG+PEG and BSA+YCl$_3$) at molecular length scales. Additionally, it examines the impact of dose rate on X-ray-induced dynamics in highly concentrated antibody-protein solutions. A comprehensive understanding of the capabilities and limitations of XPCS is essential for optimizing its potential to enhance our understanding about protein dynamics and its various applications in different disciplines.
XPCS has several notable advantages, including the ability to achieve spatial resolution at the nanoscale. Additionally, XPCS demonstrates compatibility with a wide range of sample environments, encompassing aqueous and opaque solutions. Moreover, XPCS enables the determination of collective dynamics within the studied systems. Although this approach has numerous advantages, it is also constrained by a number of obstacles. This study addresses the challenges related to radiation damage, data analysis complexities, and the necessity for coherent X-ray sources.
Furthermore, this work presents a new dimension of the research, focusing on the influence of X-ray dose rates on the corresponding dynamics in concentrated solutions of proteins. By systematically varying the dose rates, this research aims to evaluate how X-ray radiation influences protein dynamics and interactions in crowded environments. This exploration has implications for both biophysical research and the field of soft matter, where X-ray-based techniques are becoming increasingly relevant.