Early events of protein folding have been investigated by a cryo-stopped-flow method with ultraviolet circular dichroism, fluorescence and X-ray solution scattering as probes. We found that α-helices were formed very rapidly as a folding nucleus within the dead-time of the stopped-flow apparatus. In the case of ubiquitin containing α-helix and β-structure, the folding took place via α-helix-rich intermediate, contrary to the previous hypothesis of 2-state transition. This was also the case of Src SH3 domain protein containing only β-structure and other proteins so far investigated. The intermediate structure of Src SH3 domain protein folding was calculated by using a SAXS-MD program. In the studies of three homologous SH3 domain proteins (Src, Fyn and PI3K), we found that these proteins are folded via a different folding pathways.
Polarization rotation is the key for interpretation of the piezoelectricity in Pb（Ti1-xZrx）O3（PZT）and other piezoelectric ceramics. We found the monoclinic phase in BiCo1-xFexO3（x～0.7）that is isostructural with the low temperature phase of PZT at the morphotropic phase boundary（MPB）. Precise structural analysis by electron diffraction and powder synchrotron X-ray diffraction revealed that the monoclinic perovskite BiCo1-xFexO3 exhibits Cm symmetry and showed polarization rotation as functions of composition and temperature. The second order structural transition from tetragonal to monoclinic structures was accompanied by a rotation of the polarization vector from the［001］to［111］directions of a pseudo cubic cell.
The Toll-like receptors（TLRs）are a family of pattern-recognition receptors that recognize pathogen-associated molecular patterns and activate innate immune system. TLR8 is activated by single-stranded RNA or synthetic imidazoquinoline compounds. We determined the crystal structures of unliganded and liganded TLR8 to clarify signaling and activation mechanism of TLR8. TLR8 monomer was ring-shaped structure in which N- and C-termini interacted directly. Both in the unliganded and liganded forms, TLR8 formed m-shaped dimer in which two C termini converged in the middle. Ligands were located in the two equivalent positions in the dimerization interface related by the non-crystallographic two-fold axis. The C-termini of the two TLR8 protomers were separated by 53 Å in the unliganded form; whereas, C-termini of the two monomers were brought into close proximity（～30 Å）in the liganded form, which would enable the subsequent dimerization of the TIR domains and downstream signaling.
An unconventional pseudo-tetragonal crystal structure is found in a BaTiO3 epitaxial thin film grown on a （110）SrTiO3 substrate. The unique crystal structure of the BaTiO3 film, which is markedly different from the bulk tetragonal structure, is caused by the nearly uniaxial strain due to the different strain relaxation along ［001］ and ［110］ axes.
Novel perovskite-type Bi-based piezoelectric materials which was discovered by high pressure synthesis were fabricated by MOCVD method. We also suggested a piezoresponse measurement system using synchrotron X-ray for In-situ measurement of “Polarization - Lattice strain - Electric field” at a same time.
Electronic structure of hexagonal diamond（h-DIA）was investigated by using high energyresolution electron energy-loss spectroscopy（EELS）based on transmission electron microscopy. The dielectric function of h-DIA was derived by Kramers-Kronig analysis of the EELS spectrum. Core electron excitation spectrum of h-DIA revealed density of states in conduction band,which was different distribution from that of cubic diamond. The electronic structure of h-DIA was experimentally revealed for the first time.
We have investigated the incommensurate crystal structure of the spinel CuV2S4, which exhibits incommensurate charge-density wave at 90 K, using the synchrotron powder diffraction technique. It is found that the crystal structure at 70 K has an orthorhombic unit cell with the superspace-group Imm2（0β0）with a modulation vector q＝0.7391（5）b*. By Rietveld analysis including the incommensurate modulation along the b-axis, large static atomic displacements were found at the positions of V atoms, suggesting that V atoms play an important role in a charge-density wave transition. We have found the formation of V clusters, and arrangements of the clusters form a gradation pattern along the b-axis.