High-resolution macromolecular crystallography at the FemtoMAX beamline with time-over-threshold photon detection

Abstract

Protein dynamics contribute to protein function on different time scales. Ultrafast X-ray diffraction snapshots can visualize the location and amplitude of atom displacements after perturbation. Since amplitudes of ultrafast motions are small, high-quality X-ray diffraction data is necessary for detection. Diffraction from bovine trypsin crystals using single femtosecond X-ray pulses was recorded at FemtoMAX, which is a versatile beamline of the MAX IV synchrotron. The time-over-threshold detection made it possible that single photons are distinguishable even under short-pulse low-repetition-rate conditions. The diffraction data quality from FemtoMAX beamline enables atomic resolution investigation of protein structures. This evaluation is based on the shape of the Wilson plot, cumulative intensity distribution compared with theoretical distribution, I/σ, R merge/R meas and CC1/2 statistics versus resolution. The FemtoMAX beamline provides an interesting alternative to X-ray free-electron lasers when studying reversible processes in protein crystals.

Femtosecond X-ray snapshots reveal correlated displacements of specific distal atoms in a protein crystal

“…In this work, we aimed to visualize collective movements in protein crystals and provide a model description in terms of coherent waves. Experimentally, the ps dynamics of atomic shifts in bovine trypsin was studied by fs-snapshots of crystal states at atomic resolution [30][31][32] . One of the primary questions addressed here is whether there is evidence for THz-induced elastic deformations of the protein unit cell before thermalisation completes.…”