Abstract
Protein dynamics are integral to biological function, yet few techniques are sensitive to collective atomic motions. A long-standing goal of X-ray crystallography has been to combine structural information from Bragg diffraction with dynamic information contained in the diffuse scattering background. However, the origin of macromolecular diffuse scattering has been poorly understood, limiting its applicability. We present a finely sampled diffuse scattering map from triclinic lysozyme with unprecedented accuracy and detail, clearly resolving both the inter- and intramolecular correlations. These correlations are studied theoretically using both all-atom molecular dynamics and simple vibrational models. Although lattice dynamics reproduce most of the diffuse pattern, protein internal dynamics, which include hinge-bending motions, are needed to explain the short-ranged correlations revealed by Patterson analysis. These insights lay the groundwork for animating crystal structures with biochemically relevant motions.
Highlights
Protein dynamics are integral to biological function, yet few techniques are sensitive to collective atomic motions
Conventional structure determination by X-ray crystallography relies on the intense spots recorded in diffraction images, known as Bragg peaks, that represent the average electron density of the unit cell
By studying the total X-ray scattering from triclinic lysozyme crystals both experimentally and theoretically, we were able to obtain fundamental insight into the collective motions that produce macromolecular diffuse scattering
Summary
Protein dynamics are integral to biological function, yet few techniques are sensitive to collective atomic motions. It has been common practice to heavily process images either by filtering or masking near-Bragg pixels[14,17] This treatment suppresses features that are derived from long-ranged correlations extending beyond the unit cell and may alter the information contained in the remaining signal. By combining high-quality experimental data with new processing methods, we were able to construct a highly detailed map of diffuse scattering without filtering the images This map reveals, for the first time, a surprisingly large contribution of long-ranged correlated motions across multiple unit cells, while enabling detection of protein motions in a manner that is consistent with both Bragg diffraction and diffuse scattering
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