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1.
Markus Gühr 《Synchrotron Radiation News》2016,29(5):8-12
The molecular ability to selectively and efficiently convert sunlight into other forms of energy like heat, bond change, or charge separation is truly remarkable. The decisive steps in these transformations often happen on a femtosecond timescale and require transitions among different electronic states that violate the Born-Oppenheimer approximation (BOA) [1]. Non-BOA transitions pose challenges to both theory and experiment. From a theoretical point of view, excited state dynamics and nonadiabatic transitions both are difficult problems [2, 3] (see Figure 1(a)). However, the theory on non-BOA dynamics has advanced significantly over the last two decades. Full dynamical simulations for molecules of the size of nucleobases have been possible for a couple of years [4, 5] and allow predictions of experimental observables like photoelectron energy [6] or ion yield [7–9]. The availability of these calculations for isolated molecules has spurred new experimental efforts to develop methods that are sufficiently different from all optical techniques. For determination of transient molecular structure, femtosecond X-ray diffraction [10, 11] and electron diffraction [12] have been implemented on optically excited molecules. 相似文献
2.
Eugenio Ferrari 《Synchrotron Radiation News》2016,29(3):4-9
The advent of FEL sources delivering two synchronized pulses of different wavelengths has made available a whole range of novel pump-probe experiments [1], allowing the exploration of the dynamics of matter driven to extreme non-equilibrium states by an intense ultrashort X-ray pulse and then probing the sample response at variable time delay with a second pulse [2]. 相似文献
3.
Proteins are the workhorses of living cells, providing essential functions such as structural support, signal transduction, enzymatic catalysis, transport and storage of small ligands. Atomic-resolution structures obtained with conventional X-ray crystallography show proteins essentially as static. In reality, however, proteins move and their motion is crucial for functioning. Although the structure and dynamics of proteins are intimately related, they are not equally well understood. A very large number of protein structures have been determined, but only a few studies have been able to monitor experimentally the dynamics of proteins in real time. In the last two decades, the availability of short (~100 ps) and intense (~109–1010 photons) X-ray pulses produced by third-generation synchrotrons have allowed the implementation of structural methods like time-resolved X-ray crystallography and time-resolved X-ray solution scattering that have allowed us to monitor protein motion in the nanosecond-to-millisecond timescale [1–4]. Time-resolved X-ray crystallography has been used to monitor processes such as the migration of a ligand from the protein active site to the surrounding solvent [5–7] or tertiary structural changes associated with allosteric transitions [8, 9]. On the other hand, time-resolved X-ray scattering in the so-called wide-angle X-ray scattering (WAXS) region [10] has been used to track conformational changes corresponding to large-amplitude protein motions such as the quaternary R-T transition of human hemoglobin [11–13], the relative motion of bacteriorhodopsin α-helices following retinal isomerization [14], or the open-to-close transition in bacterial phytochromes [15]. 相似文献
4.
Henry N. Chapman 《Synchrotron Radiation News》2015,28(6):20-24
X-ray free-electron lasers produce brief flashes of X-rays that are of about a billion times higher peak brightness than achievable from storage ring sources. Such a tremendous jump in X-ray source capabilities, which came in 2009 when the Linac Coherent Light Source began operations, was unprecedented in the history of X-ray science. Protein structure determination through the method of macromolecular crystallography has consistently benefited from the many increases in source performance from rotating anodes to all generations of synchrotron facilities. But when confronted with the prospects of such bright beams for structural biology, enthusiastic proposals were tempered by trepidation of the effects of such beams on samples and challenges to record data [1]. A decade after these discussions (and others in the USA) on the applications of X-ray FELs for biology, the first experiments took place at LCLS, giving results that fulfilled many of the dreams of the early visionaries. In particular, the concept that diffraction representing the pristine object could be recorded before the X-ray pulse completely vaporizes the object was validated [2], confirming predictions [3] that established dose limits could be vastly exceeded using femtosecond-duration pulses. The first experiments illuminated a path to achieve room-temperature structures free of radiation damage, from samples too small to provide useful data at synchrotron facilities, as well as providing the means to carry out time-resolved crystallography at femtoseconds to milliseconds. In the five years since, progress has been substantial and rapid, invigorating the field of macromolecular crystallography [4, 5]. This phase of development is far from over, but with both the LCLS and the SPring-8 Ångström Compact Free-electron Laser (SACLA) providing facilities for measurements, the benefits of X-ray FELs are already being translated into new biological insights. 相似文献
5.
Kensuke Tono 《Synchrotron Radiation News》2017,30(1):12-15
X-ray free electron lasers (XFELs) produce femtosecond X-ray pulses with nearly full spatial coherence and a peak power in the order of tens of GW [1, 2]. At present, two XFEL facilities, the Linac Coherent Light Source (LCLS) and SPring-8 Angstrom Compact free electron LAser (SACLA), offer research opportunities to scientists from various fields. The novel characteristics of XFELs necessitate new experimental styles, which are very different from those for conventional X-ray sources. Since many users were not familiar with these new styles in the early stage of scientific applications, user-friendly experimental systems were necessary to boost the XFEL applications into a state of practical use. XFELs are now producing unique results in, for example, structural biology [3–6], nonlinear X-ray optics [7, 8], ultrafast physics and chemistry [9–11], and high-energy-density science [12]. 相似文献
6.
Yasumasa Joti Kyo Nakajima Takashi Kameshima Mitsuhiro Yamaga Toshinori Abe Kensuke Okada 《Synchrotron Radiation News》2017,30(1):16-21
X-ray free-electron lasers (XFELs) with full spatial coherence, extreme brilliance, and ultra-fast pulse duration [1, 2] allow the investigation of complex phenomena in physics, chemistry, and biology with angstrom and femtosecond resolutions. In particular, a concept of “diffraction before destruction” [3] has been demonstrated for serial femtosecond crystallography (SFX) [4, 5] and coherent diffractive imaging (CDI) [6]. Using femto-second XFEL pulses, diffraction data are collected before radiation damage to samples has time to occur. Since samples are exchanged for each XFEL pulse, shot-to-shot data acquisition (DAQ) is mandatory to correlate the recorded data with the sample characteristics. The shot-to-shot DAQ must be synchronized with the repetition rate of the XFEL source, typically several tens to one hundred Hz for the machine based on normal-conducting accelerators. Shot-to-shot recording of XFEL pulse characteristics is also essential because they fluctuate due to the stochastic nature of a self-amplified spontaneous emission (SASE). We must carefully analyze a huge data set taking the fluctuation into account. 相似文献
7.
Takumi Goto Satoshi Matsuyama Hiroki Nakamori Yasuhisa Sano Yoshiki Kohmura Makina Yabashi 《Synchrotron Radiation News》2016,29(4):32-36
Ultra-bright and high-coherence X-rays are now being used in synchrotron radiation facilities and X-ray free electron laser facilities. X-ray focusing techniques are essential to take full advantage of these excellent X-ray light sources. To meet the strong demand, high-quality X-ray focusing optics have been developed owing to the advancement of ultraprecision machining and measurement. State-of-the-art refractive lenses [1], zone plates [2], and Laue lenses [3] can be used to achieve X-ray focusing to a spot a few tens of nanometers. 相似文献
8.
Uwe Mueller Marjolein Thunnissen Jie Nan Mikel Eguiraun Fredrick Bolmsten Antonio Milàn-Otero 《Synchrotron Radiation News》2017,30(1):22-27
The outstanding success of structural biology within the last two decades is closely related to the development and evolution of macromolecular crystallography (MX) beamlines. Indeed, many of today's synchrotron-based MX experimental sessions aim for fast but rigorous evaluations and data collections from very large numbers of samples [1–7]. To facilitate this, sample changing on most MX beamlines is now carried out by robots and the centering of a crystal in the X-ray beam to micrometer precision is now automatically performed using either optical or diffraction-based techniques [8]. Once a crystal is centered, users have a wide array of options at their disposal to prepare any given experiment. This includes: X-ray fluorescence (XRF) [9] analysis to confirm the presence of anomalous scatterers in crystals; X-ray absorption near-edge scans (XANES) to determine the best X-ray wavelengths for MAD/SAD data collection [10]; and the probing of the diffraction properties of crystals to determine the best crystal, or area of a crystal [11], for data collection. All of these operations are now also automated, as is the collection of the final diffraction data set either from single or multiple crystals and the subsequent data analysis and reduction. 相似文献
9.
Ambient-pressure X-ray photoelectron spectroscopy (APXPS) has contributed greatly to a wide range of research fields, including environmental science [1], catalysis [2], and electrochemistry [3], to name a few. The use of this technique at synchrotron facilities primarily focused on probing the solid/gas interface; however, it quickly advanced to the probing of liquid/vapor interfaces [4, 5] and solid/liquid interfaces through an X-ray-transparent window [6–8]. Most recently, combining APXPS with “Tender” X-rays (~2.5 keV to 8 keV) on beamline 9.3.1 at the Advanced Light Source in Lawrence Berkeley National Laboratory (which can generate photoelectrons with much longer inelastic mean free paths) has enabled us to probe the solid/liquid interface without needing a window [9]. This innovation allows us to probe interfacial chemistries of electrochemically controlled solid/liquid interfaces undergoing charge transfer reactions [9]. These advancements have transitioned APXPS from a traditional surface science tool to an essential interface science technique. 相似文献
10.
11.
Since the first crystal structures were determined by the Braggs just over 100 years ago, crystallography has rapidly evolved in parallel with developments in photon, neutron, and electron sources to become the “go-to” technique for structure-function studies. It can provide atomic resolution structural information on an entire three-dimensional molecular or crystalline structure and is used from the study of bulk phase materials through to individual protein molecules [1, 2]. 相似文献
12.
Hirokatsu Yumoto Takahisa Koyama Satoshi Matsuyama Yoshiki Kohmura Kazuto Yamauchi Tetsuya Ishikawa 《Synchrotron Radiation News》2016,29(4):27-31
Ellipsoidal mirror optics can produce a smaller, two-dimensional focus with diffraction-limited properties than is possible when using mirror optics in Kirkpatrick–Baez (K–B) geometry [1]. This is because ellipsoidal focusing mirrors can be designed such that they have a larger numerical aperture in the sagittal focusing direction as compared to that in the meridional focusing direction. Although ellipsoidal focusing mirrors have this crucial advantage over K–B optics, K–B optics are widely utilized as micro-/nano-focusing devices [2–8] in synchrotron radiation facilities and X-ray free electron laser facilities [9, 10]. Figure 1 shows a schematic of focusing mirror optics; Figure 1(a) shows the ellipsoidal mirror and Figure 1(b) the K–B mirror arrangement. In K–B geometry, two mirrors with a one-dimensionally curved surface, such as an elliptical cylinder, are orthogonally arranged in tandem to reflect and focus light independently in a direction perpendicular to each other under grazing-incidence conditions. Ellipsoidal focusing mirrors, which can generate a two-dimensional focusing beam by a single reflection, have a highly sloped surface with a two-dimensional aspherical shape, when compared to elliptical-cylinder mirrors that are used for line-focusing in K–B geometry. In addition, surface shapes of nano-focusing mirrors must be fabricated with nanometer-level accuracy. Therefore, fabrication of ellipsoidal nano-focusing mirrors is extremely difficult. There are no reports on ellipsoidal nano-focusing mirrors in the hard X-ray region with superior performances to provide diffraction-limited beams. 相似文献
13.
Ray Conley Nathalie Bouet Yong S. Chu Xiaojing Huang Hyon Chol Kang Albert T. Macrander 《Synchrotron Radiation News》2016,29(4):16-20
X-rays are intrinsically capable of being used for the study of non-periodic objects with atomic resolution, with high penetration, in applied electromagnetic fields, and in fluids and gases. For direct imaging via nanofocused X-ray beams, reflective [1], refractive [2], and diffractive [3, 4] optics are used in various approaches for high-resolution imaging. Diffractive X-ray optics are endowed with the highest numerical aperture, in principle allowing focusing of X-rays to sub-nanometer dimensions. Lithographically produced Fresnel zone plates (FZP) find broad deployment around the globe, in both nanofocusing and full-field imaging approaches, and have, for many years, been workhorse optics in both synchrotron-based and laboratory-based X-ray imaging systems [4]. A FZP consists of a series of radially symmetric rings, which are known as Fresnel zones, which alternate between transparent and opaque. Radiation traversing into the FZP diffracts around the opaque zones, which are placed in an arrangement where light constructively interferes at the focal plane. 相似文献
14.
Kiyoshi Ueda 《Synchrotron Radiation News》2016,29(5):3-7
In recent years, short wavelength free electron lasers (FELs) have opened up access to ultrafast electronic and structural dynamics in matter. Currently, four FEL facilities are in operation in the world. FLASH [1] in Germany and FERMI [2] in Italy cover the range from extreme ultraviolet (EUV) to soft X-rays, while LCLS [3] in the U.S. and SACLA [4] in Japan provide pulses in the hard X-ray regime. In addition, an upgrade version of SCSS [5], nicknamed SCSS+, has also just started user operation as a beamline of SACLA [6]. These FELs deliver coherent pulses combining unprecedented power densities up to ~1020 W/cm2 and extremely short pulse durations down to a few femtoseconds. The intense coherent FEL pulse focused down to ~1 μm2 makes single-shot diffractive imaging of nano-crystals or even non-crystallized bio-samples as well as other small objects a reality. Time-resolved spectroscopic and structural studies on the timescale of femtoseconds, having FEL pulses as a probe, allow us to probe electrons and atoms in action. Additionally, since FEL pulses are in a new regime of intensity, they are opening up new research fields that exploit the interaction between intense short wavelength pulses and matter, leading to matter at extremely high energy. Relevant theories dealing with such extreme conditions are also rapidly growing. 相似文献
15.
C.-L. Dong J.-W. Chiou H.-M. Tsai H.-W. Fu H.-J. Lin C.T. Chen 《Synchrotron Radiation News》2017,30(2):24-29
Owing to the current energy crisis and extreme changes in the global climate, there is great interest in finding renewable energy resources. Vast progress has been made in the development of new materials related to renewable energy, and their physical/chemical properties can be tailored by nanostructuring and other advanced synthetic approaches. In many important energy systems, such as solar hydrogen systems, the atomic/electronic structures of materials and fundamental interfacial phenomena of systems critically determine the energy conversion efficiency of materials [1, 2]. Without knowledge of the fundamental electronic structures of the materials during conversion reactions, better engineering of the material for practical use is difficult. Understanding and controlling the interfaces in energy generation/conversion/storage materials requires in-situ/operando approaches [3, 4]. The Taiwan Photon Source (TPS) Soft X-ray Spectroscopic beamline provides the capabilities for X-ray absorption (XAS) and X-ray emission (XES) spectroscopies, which can be utilized to investigate unoccupied (conduction-band) and occupied (valence-band) electronic states, respectively. Moreover, resonant inelastic X-ray scattering (RIXS) can be used to study intra-band (including d-d or f-f excitations) and inter-band (charge transfer) transitions [5, 6]. The former provides details about electronic energy splitting in various crystal fields and the latter involves electron transfer between a metal and a ligand, which determines chemical activity [7, 8]. 相似文献
16.
Zehra Sayers 《Synchrotron Radiation News》2013,26(6):24-25
The potential of X-rays for the non-invasive investigation of the interior of bulky samples has long been recognized and their penetration depth is presently widely exploited [1]. Although initially third generation synchrotron sources were almost exclusively the realm of academic scientific experiments, the use of synchrotron light for industrial research is becoming increasingly important and relevant for both technology development and non-destructive testing, in particular when the requirements in terms of spatial, temporal, and density resolution are exceptional. 相似文献
17.
The method of synchrotron X-ray protein footprinting (XF-MS) is used to determine protein conformational changes, folding, protein-protein and protein-ligand interactions, providing information which is often difficult to obtain using X-ray crystallography and other common structural biology methods [1–3]. The technique uses comparative in situ labeling of solvent-accessible side chains by highly reactive hydroxyl radicals (?OH) in buffered aqueous solution under different assay conditions. In regions where a protein is folded or binds a partner, these ?OH susceptible sites are inaccessible to solvent, and therefore protected from labeling. The ?OH are generated by the ionization of water using high-flux-density X-rays. High-flux density is a key factor for XF-MS labeling because obtaining an adequate steady-state concentration of hydroxyl radical within a short irradiation time is necessary to minimize radiation-induced secondary damage and also to overcome various scavenging reactions that reduce the yield of labeled side chains. 相似文献
18.
Bo Hu Phillip Geissbuhler Larry Sorensen Stephen D. Kevan Jeffrey B. Kortright Eric E. Fullerton 《Synchrotron Radiation News》2013,26(2):11-19
X-ray sources are exceptional tools for studying the structure of matter down to atomic-length scales, but across a wide range of fields there are samples that have remained notoriously difficult to study, such as airborne particles, particles in solution, membrane proteins, and macromolecular complexes. The advancement of imaging techniques to address these elusive samples has been a big motivation for constructing new X-ray light sources. Fourth-generation light sources, commonly called X-ray free-electron lasers (XFELs) [1], represent a huge step forward, with upwards of nine orders of magnitude increase in peak brightness for hard X-rays. As of 2012, four such XFELs are already productively operational (in Germany [2], the U.S. [3], Japan [4], and Italy [5]), with at least five more planned for the next 10 years. These lasers produce femtosecond pulses of extremely intense coherent radiation through the positive feedback between a co-moving electron bunch and the radiation it emits when they traverse an extended undulator. This process creates remarkably strong, tunable probes that will undoubtedly change the way we examine nanoscale structure and dynamics. 相似文献
19.
Interest in radiation damage to macromolecules during structural experiments has a long history dating back to 1962, when the first room-temperature study of the phenomenon was carried out on crystals of myoglobin [1], and this interest has not abated over the last few years, since there remains a need to understand both the parameters that affect radiation damage progression and also the artifacts produced by it. Although there is now a growing body of literature pertaining to this topic, clear and foolproof methods for experimenters to routinely minimize damage have yet to emerge. Additionally, radiation damage is also a concern and limiting problem in other methods used in structural biology, such as electron microscopy [2] and SAXS [3, 4]. However, the recently available free electron lasers (FELs) have presented the possibility and promise that samples will give “diffraction before destruction”; is this indeed the “cure” for the challenges of radiation damage? 相似文献
20.
The fourth international user workshop focusing on high-power lasers at the Linac Coherent Light Source (LCLS) was held in Menlo Park, CA, USA, on October 3–4, 2016 [1–3]. The workshop was co-organized by Los Alamos National Laboratory and SLAC National Accelerator Laboratory (SLAC), and garnered the attendance of more than 110 scientists. Participants discussed the warm dense matter and high-pressure science that is being conducted using high-power lasers at the LCLS Matter in Extreme Conditions (MEC) endstation. During the past year, there have been seven journal articles published from research at the MEC instrument [4–10]. The specific topics discussed at this workshop were experimental highlights from the past year, current status and future commissioning of MEC capabilities, and future facility upgrades that will enable the expanded science reach of the facility. 相似文献