The structure analysis of methane hydrate was performed with neutron powder diffraction. The distribution of hydrogen was observed as the scattering length density distribution with a combination of Rietveld method and maximum entropy method. The scattering length density showed that there was a low-density D site at a particular part of the D2O cage at low temperature. This result suggests that a spatial disorder of the D atom occurs at a particular site. For the methane molecules (CH4 or CD4), the density distribution of the C and hydrogen (H or D) atoms was observed separately in the scattering length density image because of the orientational disorder.
Biosynthesis of mucin-type O-glycan is initiated the transfer of GalNAc which is catalyzed by pp-GalNAc-Ts. We previously cloned and characterized human pp-GalNAc-T10, which exhibited significant activity toward GalNAC-peptides but negligible activity toward non-glycosylated peptides. We determined crystal structures of this isozyme. The structure successfully explains the substrate specificity and the GalNAc position of the products. pp-GalNAc-T10 comprises two domains, catalytic and lectin domains. GalNAc-Ser are bound to only the lectin b subdomain. The distance between the catalytic center and the carbohydrate-binding site on the b subdomain influences the positions of GalNAc glycosylation on Serll-GalNAc-IgA-hinge peptide as a substrate. In addition, an alternative glyco-peptide recognition site is indicated for the reaction toward Thr4-GalNAc-IgA-hinge peptide. Two recognition modes were clearly differentiated by alanine substitutions.
Family of Rabll-interacting protein 3 (FIP3) and FIP4 are dual effectors for Rabll and ARF5/ARF6 involved in membrane delivery from recycling endosomes to the plasma membrane during cytokinesis. Here, we determined the crystal structure of Rabll in complex with the Rabll-binding domain (RBD) of FIP3. The long amphiphilic α-helix of the FIP3-RBD forms a parallel coiled-coil homodimer, with two symmetric interfaces with two Rabll molecules. The hydrophobic side of the FIP3-RBD is involved in homodimerization and interacted with the Rabll switch 1 region, whereas the opposite hydrophilic side interacts with the Rabll switch 2 and is the major factor contributing to the binding specificity.
The development of actuators based on materials that reversibly change shape and/or size in response to external stimuli has attracted interest once in a while. A particularly intriguing possibility is offered by light-responsive materials, which allow remote operation without the need for direct contact to the actuator. Here we show that molecular crystals based on diarylethene chromophores exhibit rapid and reversible macroscopic changes in shape and size induced by ultraviolet and visible light. The deformed crystals are thermally stable, and switch back to the original state on irradiation with visible light. The diarylethene crystals respond in about 25 microseconds in shape changes and they can move microscopic objects, making them promising materials for possible light-driven actuator applications.
We have reported the crystal structure of the superconducting systems Y2C3 and Li2Pd3B without inversion symmetry. The structure of Y2C3 has the dumbbell-like C-C unit occupying polyhedrally-coordinated void, while the structure of Li2Pd3B has three-dimensional framework of the BPd6 octahedron, which exists at the clearance gap of the Li partial structure. The superconducting transition temperature is strongly dependent on the structural change of the C-C distance in the Y2C3 system and of the distortion of the BPd6 octahedron in the Li2Pd3B system.
High-pressure single crystal X-ray diffraction experiments and FT-IR observations of natural chondrodite, synthesized OH-chondrodite and phase A have been conducted. FT-IR observations of natural chondrodite showed that the peaks shifted to lower wave-numbers with increasing pressure. This suggested that hydrogen bonding would be formed in its structure under highpressure conditions. As results from X-ray diffraction experiments under high-pressure conditions, bulk moduli of these minerals were determined and their crystal structures were refined. The relationships between bulk modulus and packing index and summation of the filling factor for humite minerals and some DHMS phases were plotted on a simple positive line, respectively. Also, as results from structural refinements under high-pressure conditions, the polyhedral bulk moduli were obtained. Compression mechanism of humite minerals was controlled by the octahedral compression mainly.
Ribonuclease P (RNase P) is a ribonucleoprotein complex involved in the removal of 5' leader sequences from tRNA precursors (pre-tRNA) . We have determined the crystal structures of all protein subunits Ph1771p, Ph1877p, Ph1601p, Ph1481p, and Ph1496p. Furthermore, the essential amino acid residues in these proteins for the P. horikoshii RNase P activity were assigned by site-directed mutagenesis.