Serial femtosecond crystallography (SFX) allows structures to be determined with minimal radiation damage. However, phasing native crystals in SFX is not very common. Here, the structure ...determination of native lysozyme from single‐wavelength anomalous diffraction (SAD) by utilizing the anomalous signal of sulfur and chlorine at a wavelength of 1.77 Å is successfully demonstrated. This sulfur SAD method can be applied to a wide range of proteins, which will improve the determination of native crystal structures.
The Shanghai Soft X‐ray Free‐Electron Laser (SXFEL) is the first X‐ray free‐electron laser facility in China. The SASE beamline, which consists of a pink‐beam branch and a mono‐beam branch, is one of ...the two beamlines in the Phase‐I construction. The pink‐beam branch opened for users in 2023 after successful first‐round beamline commissioning. In this paper, the design of the beamline is presented and the performance of the pink‐beam branch is reported. The measured energy‐resolving power of the online spectrometer is over 6000 @ 400 eV. The focusing spot size of the pink beam is less than 3 µm in both the horizontal and vertical at the endstation.
The design and first‐round commissioning results of the SASE beamline at the Shanghai Soft X‐ray FEL facility are presented.
In oxygenic photosynthesis, light-driven oxidation of water to molecular oxygen is carried out by the oxygen-evolving complex (OEC) in photosystem II (PS II). Recently, we reported the ...roomtemperature structures of PS II in the four (semi)stable S-states, S₁, S₂, S₃, and S₀, showing that a water molecule is inserted during the S₂ → S₃ transition, as a new bridging O(H)-ligand between Mn1 and Ca. To understand the sequence of events leading to the formation of this last stable intermediate state before O₂ formation, we recorded diffraction and Mn X-ray emission spectroscopy (XES) data at several time points during the S₂ → S₃ transition. At the electron acceptor site, changes due to the two-electron redox chemistry at the quinones, QA and QB, are observed. At the donor site, tyrosine YZ and His190 H-bonded to it move by 50 μs after the second flash, and Glu189 moves away from Ca. This is followed by Mn1 and Mn4 moving apart, and the insertion of OX(H) at the open coordination site of Mn1. This water, possibly a ligand of Ca, could be supplied via a “water wheel”-like arrangement of five waters next to the OEC that is connected by a large channel to the bulk solvent. XES spectra show that Mn oxidation (τ of ∼350 μs) during the S₂ → S₃ transition mirrors the appearance of OX electron density. This indicates that the oxidation state change and the insertion of water as a bridging atom between Mn1 and Ca are highly correlated.
The design and performance of a soft X‐ray free‐electron laser (FEL) beamline of the SPring‐8 Compact free‐electron LAser (SACLA) are described. The SPring‐8 Compact SASE Source test accelerator, a ...prototype machine of SACLA, was relocated to the SACLA undulator hall for dedicated use for the soft X‐ray FEL beamline. Since the accelerator is operated independently of the SACLA main linac that drives the two hard X‐ray beamlines, it is possible to produce both soft and hard X‐ray FEL simultaneously. The FEL pulse energy reached 110 µJ at a wavelength of 12.4 nm (i.e. photon energy of 100 eV) with an electron beam energy of 780 MeV.
The status of a soft X‐ray free‐electron laser beamline at SACLA is reported.
The effect of undulator field harmonics on spontaneous and stimulated undulator radiation, both on and off the undulator axis, is studied. Bessel factors for the undulators with field harmonics have ...been analytically calculated and numerically verified. The influence of the third undulator field harmonic on single‐pass free‐electron laser radiation is explored. Harmonic generation at the LCLS and SPring‐8 free‐electron lasers is modeled and analyzed.
Accurate and simple‐to‐compute analytical formulation for the effect of the high undulator field harmonics on spontaneous and stimulated undulator radiation is provided. It is applicable to any undulator and confirmed by comparison with LCLS and SPring‐8 FEL experiments and with SPECTRA numerical simulations.
We have used the framework of the dispersion equation to study coherent Smith-Purcell (SP) radiation induced by a relativistic magnetized electron beam in the absence of a resonator. As an important ...example of the application of the obtained results of our previous paper JMO v.57, 2060, (2010) the growth rate of SP FEL in the case with a rectangular grating was calculated. The growth rate of the instability is proportional to the square root of the electron beam current. The calculated results are consistent with the experimental data obtained by Urata et al. Phys. Rev. Lett. 80, 516 (1998).
Structures of the four reaction states of the adenine riboswitch aptamer domain, including a transient intermediate state were solved by serial femtosecond crystallography. The structures not only ...demonstrate the use of X‐ray free‐electron lasers for RNA crystallography but have also proven that transient states can be determined in real time by mix‐and‐inject crystallography. These results illustrate the structural basis for the ligand‐induced conformational changes associated with the molecular ‘switch’.
Using an X‐ray free‐electron laser and a mix‐and‐inject serial crystallography approach, we have captured the ligand‐induced structural conversion of the adenine riboswitch aptamer domain from apo, to intermediate, to final bound states. Like synchronized swimmers, millions of molecules undergo large conformational changes within the crystal lattice. These results provide the structural basis for the switching mechanism for regulating gene expression. Image: Joseph Meyer, Scientific Publications Graphics and Media, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research.
In this article, the theory of the spectral properties of undulator radiation and the free electron laser (FEL) gain in staggered undulator has been discussed. The important contributions of the ...pole-to-pole gap parameter and the finite larmor radius effects of the electron are included in the analysis. A finite electron larmor radius of the electron introduces azimuthal bunching through cyclotron motions and the axial electron bunching degrades. The interaction of the electron and the electromagnetic wave is driven away from the resonance and causes reduction in the FEL gain. An estimate of the gain reduction is presented through an analytical calculation.
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