The technique of small-angle neutron scattering is used to study structures of size on the order of 1 nm or larger. This article briefly introduces the technique for crystalline matter, crystalline matter with imperfection, and noncrystalline matter with middle range order and the importance of the technique in materials and life science. The present status and the future plan for the technique are also presented with the idea of complimentary utilization of the technique with other scattering techniques.
Measurement of total scattering, which includes both the Bragg peaks and the diffuse scattering, can give information about the short-range structure of materials. This is quite useful for understanding the structure of liquid, glasses and amorphous materials. On the other hand, since thermal neutrons used for scattering experiments have energies in the meV range, which is close to the phonon energy, scattering by a phonon causes a fractional change in the neutron energy. This allows an accurate measurement of the energy change and makes neutrons an ideal tool for measuring phonon dispersion. Several experimental methods and examples are described.
Ionic diffusion, chemical bonding, and structural change in supersonic conductors are reviewed and discussed based on NMR investigation. The relations between ionic diffusion and bonding are discussed in the silver halides, alkali halides, copper halides. The structural change and ionic diffusion are also discussed in the major electrode materials, LiCoO2 and LiNiO2.
Computer simulation method of powder diffraction profile from the specimen with planer defects such as stacking faults and intergrowth is reviewed. The matrix method, introduced by Hendricks and Teller and developed to the general solution method by Kakinoki and Komura, is summarized, and transformation into the powder pattern profile is presented in outline. Probability matrices of layer sequences and calculated profiles using the matices are reported for several examples, SiC, Li-Mn-oxide, Cu3GdS3 and Bi1.83Sr1.80Ca1.78Cu3Oy.
On the neptunium science, 237Np Mössbauer spectroscopy and general feature of neptunium compounds with various valences are outlined. Then, correlations between isomer shifts and crystal structures of neptunyl (V, VI) compounds were discussed.
The crystal structure of the catalytic domain of human recombinant poly (ADP-ribose) polymerase (PARP) complexed with a potent inhibitor, FR257517, was solved at 3.0 Å resolution. The fluorophenyl part of the inhibitor induces an amazing structural change in the active site of PARP by motion of the side chain of the amino acid, Arg878, which forms the bottom of the active site. Consequently, a corn-shape hydrophobic subsite, which consists of the side chains of Leu769, Ile879, Pro881, and the methylene chain of Arg878, newly emerges from the well-known active site. This observation should provide a new concept in PARP inhibitor design.
The crystalline structure and thermal behavior of new types of bacterial copolyester, poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) and polyhydroxybutyrate, PHB have been explored by means of wide-angle x-ray diffraction (WAXD) and infrared (IR) spectroscopy. It has been found from the temperature dependent variations of the WAXD pattern and IR spectra that C-H…O hydrogen bonding between C=O groups and CH3 groups along the a axis and that the interactions are broken little by little from just above room temperature. The C-H…O hydrogen bonding between C=O groups and CH3 groups along the a axis may explain chain folding plane parallel to the a axis direction of PHB.
Creatininase from Pseudomonas putida is a member of the urease-related amidohydrolase superfamily.The crystal structures of Mn-activated creatininase, Mn-activated creatininasecreatine complex, and native creatininase have been determined. We found the cloverleafshaped creatininase hexamer to be roughly 100 Å in diameter and 50 Å in thickness and arranged as a trimer of dimers with 32 (D3) point group symmetry. Based on the high-resolution crystal structure of the creatininase-creative complex, we propose a new two-step catalytic mechanism possibly common to creatininases.