Femtosecond X-ray free-electron lasers: A new tool for studying nanocrystals and single macromolecules (original) (raw)
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Self-terminating diffraction gates femtosecond X-ray nanocrystallography measurements
Nature Photonics, 2011
X-ray free-electron lasers have enabled new approaches to the structural determination of protein crystals that are too small or radiation-sensitive for conventional analysis 1. For sufficiently short pulses, diffraction is collected before significant changes occur to the sample, and it has been predicted that pulses as short as 10 fs may be required to acquire atomic-resolution structural information 1-4. Here, we describe a mechanism unique to ultrafast, ultra-intense X-ray experiments that allows structural information to be collected from crystalline samples using high radiation doses without the requirement for the pulse to terminate before the onset of sample damage. Instead, the diffracted X-rays are gated by a rapid loss of crystalline periodicity, producing apparent pulse lengths significantly shorter than the duration of the incident pulse. The shortest apparent pulse lengths occur at the highest resolution, and our measurements indicate that current X-ray free-electron laser technology 5 should enable structural determination from submicrometre protein crystals with atomic resolution.
Russian Journal of Physical Chemistry B, 2014
X ray serial nanocrystallography is a new technique for determining the three dimensional struc ture of biological macromolecules from data on the diffraction of ultrashort pulses generated by X ray free electron lasers. The maximum achievable resolution for a set of experimental data as a function of the sample sizes and parameters of the equipment is estimated based on simulations of the diffraction process with allow ance for changes in the electronic structure of the atoms of the sample under the influence of X rays. Esti mates show that nanocrystallography greatly enhances the possibilities of X ray analysis, reducing the requirements for the minimum permitted size of the crystals and enabling to explore poorly crystallizable molecular objects, such as many membrane proteins and complexes of macromolecules.
Few-femtosecond time-resolved measurements of X-ray free-electron lasers
Nature Communications, 2014
X-ray free-electron lasers, with pulse durations ranging from a few to several hundred femtoseconds, are uniquely suited for studying atomic, molecular, chemical and biological systems. Characterizing the temporal profiles of these femtosecond X-ray pulses that vary from shot to shot is not only challenging but also important for data interpretation. Here we report the time-resolved measurements of X-ray free-electron lasers by using an X-band radiofrequency transverse deflector at the Linac Coherent Light Source. We demonstrate this method to be a simple, non-invasive technique with a large dynamic range for single-shot electron and X-ray temporal characterization. A resolution of less than 1 fs root mean square has been achieved for soft X-ray pulses. The lasing evolution along the undulator has been studied with the electron trapping being observed as the X-ray peak power approaches 100 GW.
Analytical Chemistry, 2013
Atomic resolution structures of large biomacromolecular complexes can now be recorded at room temperature from crystals with submicrometer dimensions using intense femtosecond pulses delivered by the world’s largest and most powerful X-ray machine, a laser called the Linac Coherent Light Source. Abundant opportunities exist for the bioanalytical sciences to help extend this revolutionary advance in structural biology to the ultimate goal of recording molecular-movies of noncrystalline biomacromolecules. This Feature will introduce the concept of serial femtosecond crystallography to the nonexpert, briefly review progress to date, and highlight some potential contributions from the analytical sciences.
Proceedings of the …, 2012
The ultrabright femtosecond X-ray pulses provided by X-ray freeelectron lasers open capabilities for studying the structure and dynamics of a wide variety of systems beyond what is possible with synchrotron sources. Recently, this "probe-before-destroy" approach has been demonstrated for atomic structure determination by serial X-ray diffraction of microcrystals. There has been the question whether a similar approach can be extended to probe the local electronic structure by X-ray spectroscopy. To address this, we have carried out femtosecond X-ray emission spectroscopy (XES) at the Linac Coherent Light Source using redox-active Mn complexes. XES probes the charge and spin states as well as the ligand environment, critical for understanding the functional role of redox-active metal sites. Kβ 1,3 XES spectra of Mn II and Mn 2 III,IV complexes at room temperature were collected using a wavelength dispersive spectrometer and femtosecond X-ray pulses with an individual dose of up to >100 MGy. The spectra were found in agreement with undamaged spectra collected at low dose using synchrotron radiation. Our results demonstrate that the intact electronic structure of redox active transition metal compounds in different oxidation states can be characterized with this shotby-shot method. This opens the door for studying the chemical dynamics of metal catalytic sites by following reactions under functional conditions. The technique can be combined with X-ray diffraction to simultaneously obtain the geometric structure of the overall protein and the local chemistry of active metal sites and is expected to prove valuable for understanding the mechanism of important metalloproteins, such as photosystem II. energy-dispersive XES | Kβ emission lines | femtosecond x-ray spectroscopy T he first X-ray free-electron laser (XFEL) operating in the hard X-ray regime (1), the Linac Coherent Light Source (LCLS), produces ∼5to 400-fs X-ray pulses with up to ∼10 12 photons per pulse at 6-10 keV at a repetition rate of 120 Hz. Each of these X-ray pulses is intense enough to expel multiple electrons from the target, which can lead to a Coulomb explosion that destroys the sample. In a shot-by-shot experiment, data are collected from each pulse before the destruction of the sample, and the sample is replenished after each pulse. The feasibility of this "probebefore-destroy" approach for X-ray crystallography experiments using XFEL pulses was first demonstrated by Chapman et al. with various systems and has subsequently been corroborated by others at the LCLS (2-6).