We have solved many kinds of protein structures by the method of X-Ray crystal structure analysis to scrutinize the relationship between their structures and functions. Though the rice crytochrome c has extra eight residues at the N terminus, the structure was essentially the same as the animal ones. The structural differences between the oxidized and reduced cytochrome c were not detected, though the crystal has a different symmetry element from each other. In case of catalase, the data were collected with the oscillation photographs and the molecular replacement method was applied to solve the structure.
Extremely small ionic displacement (10-4-10-5Å) and electron redistribution in crystals induced by externally applied electric field (50-80kVcm-1) were directly detected by using a modulation X-ray diffraction method, where the small changes in the dif-fracted intensities (10-3-10-4) were measured synchronously with the alternative electric field. For LiNbO3 and LiTaO3, the displacement of the bonding electrons of Nb-O and Ta-O bonds was found to be much larger than that of the constituent ions, which may be the origin of the electro-optic effect. The temperature factor was also found to vary with the external field. For GaAs, the effective charge of Ga was determined to be positive (larger than+le) from the observed displacement of ions, contrary to most of the results reported earlier. The displacement of bond charges was found to be much smaller than that expected from Phillips, dielectric theory. The present method was proved to be useful for the dynamical analysis of metal-semiconductor and metal-insulator-semiconductor interfaces by the detection of a high electric field in the interface regions.
Structural phase transitions of NbSe3 and TaS3, which are members of MX3, are reviewed. NbSe3undergoes two charge-density-weve phase tramsitions at T1=142K and T2=58K. TaS3 undergoes Peierls phase transition at 210K. Both materials show a nonohmic electrical conduction. We also review this phenomenon briefly.