MODELLING OF DIFFUSE X-RAY SCATTERING IN PROTEIN SYSTEMS

Abstract

Currently, the solution of protein structures typically relies upon X-ray crystallography, which is able to resolve structures on Angstrom length scales. This is accomplished by focusing on the analysis of sharply defined Bragg peaks, which provide information regarding the average ensemble structure of well-ordered crystal. This is problematic as many protein systems rely on flexibility and motion to perform their functions; but this intrinsic disorder has been completely ignored in conventional crystallography. To address this gap in information, this work focuses on analyzing “diffuse scattering”, weaker, more poorly defined signals present in diffraction images that reflect minor defects in the crystal that may be reflective of protein dynamics. As of now, diffuse scattering is poorly understood and little known in the world of protein crystallography, so this work serves to model fundamental diffuse scattering principles so that the phenomenon may be better understood. To that end, a MATLAB applet was developed to model x-ray scattering in real time based on a webcam image feed. For more thorough analysis, diffraction patterns of simple 1D systems that exhibit diffuse scattering were forward modeled to demonstrate what diffuse scattering can look like.