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, Rmerge/Rmeas 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.
Highlights
X-ray diffraction studies are performed either with monochromatic or polychromatic X-rays
The streaking changed the position of the central peak while the reflection was recorded at different positions along the rocking curve [Fig. 1(b)]. This created an additional challenge for profile fitting algorithm in the data processing software X-ray Detector Software (XDS), but the default parameters were sufficient for successful 3D peak integration
We have demonstrated the feasibility of performing protein crystallographic experiments at the FemtoMAX beamline of the MAX IV synchrotron
Summary
X-ray diffraction studies are performed either with monochromatic or polychromatic X-rays. Laue diffraction occurs when polychromatic X-ray beams are used With both methods, it is necessary to obtain several projections of the diffraction pattern with different orientations of the crystal or crystals. Monochromatic diffraction images reveal only a thin slice of the reciprocal lattice, it is still possible to obtain high-quality crystal structures through averaging many partially recorded reflections (Sharma et al, 2017). This shotgun approach emerged with the development of serial crystallography where often only one projection is available from each randomly oriented crystal, either because the crystal is destroyed during
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