“Multi-probe” is a general way to investigate unknown properties of materials experimentally. In cases of material structures, various kinds of methods such as X-ray Scattering, Neutron Scattering, Electron Microscopy, Nuclear Magnetic Resonance, have been used. In these methods, Synchrotron Radiation, Free Electron Laser, Neutron, Muon and Slow Positron have common properties; these beams are supplied at large accelerator facilities, and are utilized under similar user programs. Therefore, it is an international trend to prepare common platform for the multi-probe use in order to maximize scientific output. Here we collect several examples of multi-probe studies in various fields to know how the multi-probe investigation is effective.
An advanced hydride-ion substitution method on LaFeAsO uncovered the second superconducting (SC) phase with a higher Tc of 36 K (x～0.35) in addition to the first SC phase with the maximum Tc of 26 K (x～0.1). To investigate the origin of the two SC domes and whether a certain hidden phase exists beyond the second SC phase, we have performed a multi-probe study in the range 0.40 ≤ x ≤ 0.51 using X-ray, neutron and muon beams. We discover an antiferromagnetic phase and a unique structural transition in heavily electron-doped LaFeAsO1−xHx (x～0.5), which is regarded as a second parent phase.
Crystal structure is the fundamental information in the materials science, chemistry, physics and geoscience. Electron-density distribution of ceramic materials is important, because most of material properties are governed by the electronic states. Ion-diffusion pathway is useful to understand the ion conduction mechanism. In the present paper the author briefly reviews his group’s recent research works on the crystal structure, thermal expansion, electron-density distribution and ion-diffusion pathway of some ceramic materials investigated by multiple approaches such as synchrotron X-ray powder diffraction, neutron powder diffraction, electron diffraction, first-principles electronic calculations, maximum-entropy method (MEM) and bond valence method. The crystal structure should be examined by multiple methods, because invalid structure sometimes gives good Rietveld fit.
We combine soft X-ray, hard X-ray, and neutron inelastic scattering measurements to study both spin and charge excitations in electron-doped copper oxide superconductors. Thanks to the recent development of beam sources and related experimental techniques, accessible energy range of the inelastic scattering measurements overlaps each other and it enables us to investigate spin and charge dynamics in the important but unexplored energy-momentum space of the cuprate superconductors. Our study demonstrates that complementary use of X-ray and neutron has become effective in inelastic scattering for studying electron dynamics of materials.
We have reviewed our two recent works on flow and deformation-induced polymer crystallization revealed by complementary use of SANS and SAXS. The first topic is elongation-induced crystallization of polyethylene just below the nominal melting temperature, focusing on the role of molecular weight, and the second one is inner structure of flow-induced precursor of isotactic polystyrene above the nominal melting temperature using microbeam SAXS and WAXS.
This article reports the recent structural studies on hydrogen-metal systems using X-rays and neutrons. We have focused on the interactions between interstitial hydrogen atoms and their surrounding metal atoms. The hydrogen-metal interactions provide the important knowledge to develop the high performance hydrogen absorbing alloys. The X-ray and neutron diffraction are complementary methods to investigate the structural changes of metals or hydrogen absorbing alloys induced by the absorbing hydrogen atoms. As a typical example, pressure-induced phase separation of lanthanum di-hydride are described. The X-ray diffraction measurement on lanthanum di-hydride reveals the phase separation into hydrogen-rich and hydrogen-poor phases above 11 GPa. The neutron diffraction measurement on lanthanum di-deuteride confirms the formation of NaCl-type mono-deuteride as a counterpart of the deuterium-rich phase by phase separation.
TiO2 is used as catalyst materials. We have studied surface nanostructures of a rutile TiO2 single crystal by means of accelerator-based characterization methods such as synchrotron radiation, muon and positron. These nanostructures on the surface have no three dimensional long range order. We discuss three typical methods using positron, muon and synchrotron X-ray. We present the TiO2(110)-(1×2) surface structures studied by RHEPD (Reflection High Energy Positron Diffraction) using positron which provides a surface first layer structure. Muon spin resonance is another accelerator-based new technology which provides a defect structure and a hydrogen location. PTRF-XAFS (Polarization-dependent Total Reflection Fluorescence X-ray Absorption Fine Structure) using synchrotron X-ray is a unique technique which provides a local structure for a highly dispersed metal species on oxide single crystal surfaces. These accelerator-based methods will be a new class of surface structures and properties.
Protein crystallography has been leading the structural biology field by solving molecular structures at atomic resolution. However, it has been limited in the integration of structural information of macromolecules with a dynamic nature, which can adopt various conformations in time scales of motion even in large complexes. Therefore, it is critical to use multiple methodologies to understand biological phenomena, and connect the interfaces of molecules at both molecular and atomic resolution in macromolecular assembly. “Correlated structural analysis” is a concept in structural life science to fill the gaps between structural biology techniques. In Japan, the Platform for Drug Discovery, Informatics, and Structural Life Science has been launched with diverse expertise in bioinformatics, sample production, and structure determination. The platform supports not only conventional structural studies via X-ray crystallography, but also correlated structural analysis by integrating protein crystallography, small angle X-ray scattering, NMR, and electron microscopy data.
DNA methylation and histone modifications are major epigenetic traits for regulating the various chromatin template processes in mammals. UHRF1, together with Dnmt1, is an essential factor for maintenance of DNA methylation in somatic cells. UHRF1 has five functional domains, namely UBL, tandem tudor domain (TTD), PHD finger, SRA domain and RING finger. UHRF1 has been shown to bind to histone H3 containing tri-methylated K9 (H3K9me3), but the molecular mechanism of histone H3 recognition by UHRF1 TTD-PHD domain is unclear. Here, I report the structural study of UHRF1 TTD-PHD domain, which reveals how UHRF1 recognizes multiple histone modifications on histone H3 tail.combination of X-ray crystallography, NMR and small-angle X-ray scattering reveal the higher order structure formation of UHRF1 TTD-PHD domain, structural induction of histone H3 tail and the importance of linker between TTD and PHD finger.
Structural analysis including hydrogen position is important for estimating the reaction mechanism of hydrolases. We applied neutron and X-ray structural analysis to a mysterious β-1,4 glucanase from a fungi Phanerochaete chrysosporium (PcCel45A). The joint analysis of neutron and X-ray structures showed that PcCel45A utilizing an imidic acid form of asparagine residue as a general base instead of typical acidic residues.
Recent advances that improve direct electron detectors have revolutionized structural determination of biological molecules by cryo-electron microscopy. It has brought about the advent of near atomic resolution in single-particle reconstruction even with membrane proteins of 200~400 kDa. In fact, such high-resolution structures have allowed de novo building of atomic models. This rapid progress will change the quality and quantity of the conventional hybrid approach combining cryo-electron microscopy and X-ray crystallography or light microscopy, and computational methods such as molecular dynamics will also take on added significance to create integrated models of huge and complex macromolecules.