The measurements of optical activity of solids were unfeasible for more than 170 years since its discovery in 1811, due to coexisting large birefrinigences. We developed an optical apparatus named HAUP (high accuracy universal polarimeter), which enabled us to measure simultaneously optical activity, birefringence and rotation of indicatrices of any crystals, even belonging to the monoclinic and triclinic systems. The outstanding features of the HAUP are explained first. The indispensable utility of optical activity in researches in material sciences is demonstrated by showing our results obtained by the HAUP.
Serine proteases have been classified into three groups on the basis of their substrate specificities: those with broad substrate specificity (subtilisin), those that recognize and cleave after positively charged residues of lysine and ariginine (trypsin), and those that cleave after negatively charged residues of glutamic and aspartic acid (V8 protease) . The first two categories are structurally well characterized, but no three-dimensional structure has been reported for protease with acidic amino acid specificity. In this study, the structure of SFase-2, a serine protease with broad substrate specificity from Streptomyces fradiae has been determined by X-ray analysis and is possible to predict the structure of SFase-1, an acidic amino acid specific protease from the same organism.
The exsistence of incommensurate composite crystals SrxTiS3 (x=1.1-1.2) was revealed, and the powder X-ray diffraction patterns were assigned using a trigonal symmetry and four integers. The crystal structure was analyzed on the basis of the four-dimensional superspace group PR.3m1s using powder X-ray diffraction data and the Rietveld analysis process. The crystals are composed of columns of face-shared polyhedra, (TiS6/2) ∞, and rows of Sr, and both are parallel to the c-axis.