Protein crystallization experiment in space has been performed for more than 20 years. Although microgravity was expected to affect crystallization process to form crystals of better quality, it could not meet the expectation of the contribution to structural biology. JAXA has started ‘JAXA-GCF project’ for protein crystallization experiment in space since 2002. In the project, we performed crystallization experiments of Alpha-Amylase and Lysozyme in space and obtained crystals of very high quality with 0.89 Å and 0.88Å maximum resolution. We introduce this unique project, our recent results, and future aspects.
X-ray intensity interferometry with high-resolution monochromator was developed at the SPring-8 coherent X-ray beamlines. Transverse and longitudinal X-ray coherence properties, as well as electron beam parameters in the storage ring, were determined in high accuracy. Application to XFEL diagnostics is discussed.
Crystal structures of Co-based layered cuprates, CoSr2 (Y, Ce) s8Cu2O5+2s (s=1-3), have been investigated by high-resolution electron microscopy (HREM) and electron diffraction (ED) techniques. For all the phases ED patterns showed double periodicity along a direction parallel to the CoO layers, indicating a regular alternation of two types of CoO4-tetrahedra chains within the layers. Also seen was ordering of the chains along the layer-stacking direction for the s=1 phase. For the other phases the investigation revealed complete disordering of the chains along the layer-stacking direction. This implies that the interlayer ordering is mainly controlled by the distance between the neighboring CoO layers.
Recent human genome projects have revealed that exons encoding proteins count only a few percents, whereas many kinds of repetitive sequences occupy more than 50 % of genome. Some of the latter are related to genetic diseases, but their biological functions and structures are still unknown. Two X-ray structures of a short DNA fragment of d (gcGA [G] 1Agc) show that four base-intercalated duplexes are assembled to form an octaplex at a low K+ concentration, in which the eight G5 residues form a stacked double G-quartet in the central part. At a higher K+ concentration, however, the octaplex is split into just two halves. These structural features suggest a folding process according to a double Greek-key motif for eight tandem repeats of d (ccGA [G] 4Agg) found in Variable number of tandem repeat (VNTR) immediately adjacent to the human pseudoautosomal telomere. Such a packaging of the repeats could facilitate slippage of a certain VNTR sequence during DNA replication, to induce length polymorphism by increasing or decreasing of the repeats.
Pyrochlore oxides have the general chemical formula A2B2O7 or A2B2O6O', where A is a larger cation and B is a smaller transition metal cation. The ideal pyrochlore structure contains a tetrahedral network called the pyrochlore lattice, which has been studied extensively in order to elucidate the effect of geometrical frustration on the properties of localized spin and itinerant electron systems. Recently, superconductivity was found in Cd2Re2O7 at Tc= 1.0 K for the first time in the family of pyrochlore oxides. Although the mechanism of the superconductivity appears to be conventional, it exhibits unique successive structural phase transitions at high temperatures accompanied by large changes in physical properties. Very recently, new pyrochlore oxides AOs2O6 with A = K, Rb, and Cs were discovered, which show superconductivity at 9.6 K, 6.3 K, and 3.3 K, respectively. Although the nature of superconductivity on these β-pyrochlore superconductors is not clear at the moment, we believe that interesting physics is involved on the basis of electron correlations on the pyrochlore lattice.
Acellular slime mold, Physarum polycephalum, has a unique wound-healing system. When cytoplasm of plasmodia is exposed to extracellular fluid, calcium binding protein 40 (CBP40) seals damaged areas, forming large aggregates in a Ca2+ dependent manner. Part of the CBP40 is truncated at the N terminus by a proteinase in plasmodia (CBP40Δ), which does not aggregate in the Ca2+-bound form. Here we report the crystal structures of CBP40Δ in both the metal-free and the Ca2+-bound states. Both structures consist of three domains : coiled-coil, intervening, and EF-hand. The topology of the EF-hand domain is similar to that of calpain. The N-terminal half of CBP40Δ interacts with the C-terminal EF-hands through a large hydrophobic interface, necessary for high Ca2+ affinity. Conformational change upon Ca2+ binding is small ; however, the structure of CBP40Δ provides novel insights into the mechanism of Ca2+-dependent oligomerization.
Magneto-structural correlation of three nitronyl nitroxide derivatives carrying imidazol-2-yl, benzimidazol-2-yl, and naphth [2, 3-d] imidazol-2-yl rings as hydrogen-bonding sites is described. In these crystals, an intermolecular hydrogen bond has a role in crystal scaffolding, and the occurrence of magnetic interaction is explained by the contact of ONCNO moieties between the neighboring molecules. In particular, we found that the T-shaped contact of ONCNO moieties is very important for the occurrence of intermolecular ferromagnetic interaction.