Analysis of the conserved P9-G10.1 metal-binding motif in hammerhead ribozymes with an extra nucleotide inserted between A9 and G10.1 residues

Hammerhead ribozymes (Rz) have catalytically important tandem G:A pairs in the core region, and we recently demonstrated that the P9-G10.1 motif (a sheared-type G:A pair with a guanine residue on the 3' side of the adenine residue) with several flanking base pairs is sufficient for capture of divalent cations, such as Mg(2+) and Cd(2+) ions that are important to maintain full activities (Tanaka et al. J. Am. Chem. Soc. 2002, 124, 4595-4601; Tanaka et al. J. Am. Chem. Soc. 2004, 126, 744-752). We also found that mutant hammerhead ribozymes that have an additional G residue inserted between A9 and G10.1 residues (the metal-binding P9-G10.1 motif) have significant catalytic activities. In this study, we demonstrate that the hammerhead ribozymes are capable of maintaining the catalytically competent structure even when the tandem, sheared-type G:A pairs were perturbed by an insertion of an additional nucleotide, whereas the chirality of the phosphorothioate at the P9 position significantly influenced the enzymatic activity for both the natural and G-inserted ribozymes.     

Shift of Optical Absorption Edge in Sol-Gel Derived Transparent BaTiO3 Gels During Aging

Transparent barium titanate (BaTiO₃) wet gels synthesized by sol-gel processing using high-concentration Ba,Ti-alkoxide solution (1.0 mol/l) were subjected to optical measurements, X-ray diffraction analysis and transmission electron microscope observations. A systematic shift of the optical absorption edge was observed for the transparent BaTiO₃ wet gels shrinking during aging at 30 and 50°C, while no shift was observed for the wet gels aged at 5°C. The crystallinity and crystallite size of the gels increased with increasing aging time and temperature. The shift of the optical absorption edge of the BaTiO₃ gels during aging was found to have a close relation to an increase in the crystallite size of the gels.     

Low-Temperature Preparation of (Ba,Sr)TiO3 Perovskite Phase by Sol-Gel Method

We have investigated on the synthesis of Ba_{1 – x}Sr_xTiO₃ (BST, x = 0.0–1.0) solid solution at low temperature by a sol-gel method using precursor solutions of Ba(OC₂H₅)₂, Sr(OC₂H₅)₂, and Ti(OCH(CH₃)₂)₄ dissolved in 2-methoxyethanol. Crystalline BST solid solution monolithic gels were obtained as dried at 90°C. Crystalline fraction of BST gels increased with increasing concentration of the precursor solution and increasing amount of the hydrolysis water used. Ba_0.4Sr_0.6TiO₃ (x = 0.6) gels from a precursor solution of 0.5 mol/l with hydrolysis water of H₂O/Ti = 50 crystallized during aging at 30°C.     

Measurements of99Tc,137Cs,237Np, Pu isotopes and241Am in sediment cores from intertidal coastal and estuarine regions in the Irish Sea

Long-lived radionuclides,⁹⁹Tc,¹³⁷Cs,²³⁷Np, Pu isotopes and²⁴¹Am were determined in the long sediment cores collected from nine intertidal sites around the west Cumbria of the Irish Sea, UK. The inventories of all nuclides measured varied considerably among the sampling sites, but generally their inventories decreased with increasing distance from Sellafield. Furthermore, the inventory ratios with respect to relationship with distance from Sellafield enabled comparison of transport behavior of⁹⁹Tc,¹³⁷Cs,²³⁷Np and²⁴¹Am compared with^239,240Pu. As a consequence, the apparent fractional rate of solution transport to the intertidal sediment was found to increase as follows:⁹⁹Tc>¹³⁷Cs>²³⁷Np>^239,240Pu≥²⁴¹Am.     

General rule for displacive phase transitions in perovskite compounds revisited by first principles calculations

A recent high pressure experiment on LaAlO3 has revealed that the compound is an exception for the "general rule" of displacive phase transition associated with zone-boundary phonons. In the present study, the experimental result is successfully confirmed by first principles calculations. The pressure dependence of phonon frequencies as well as the phase transition pressure is quantitatively well reproduced. We found that the behavior is not peculiar to LaAlO3 but rather ubiquitous. RAlO3 (R = La, Nd, Sm, and Gd) and LaGaO3 can be classified in the same group.     

Correlation between proton magnetic resonance spectroscopic lactate measurements and vascular reactivity in chronic occlusive cerebrovascular disease: a comparison with positron emission tomography

The purpose of this study is to investigate the correlation between lactate levels and cerebral vascular reactivity (VR) in regions outside an area of chronic cerebral infarction. Multivoxel proton magnetic resonance spectroscopy ((1)H-MRS) and positron emission tomography (PET) were performed in 11 patients who suffered chronic cerebral infarction. Of these 11 patients, 4 were examined before and after bypass surgery. Two regions-of-interests (ROIs) were placed outside the area of chronic infarction. One ROI was placed within a control region on the contralateral side. A lactate peak area was obtained in all ROIs. An N-acetyl aspartate (NAA) peak area was obtained in the ROI within the control region. The ratio of the lactate peak area and NAA peak area (Lct/NAA) was calculated for normalization of the lactate level, and was found to be 0.13 +/- 0. 10 (range, 0 to 0.43). The VR was recorded at 13.3 +/- 20.7% (range, - 44.3 to 68.9%), utilizing PET and administering acetazolamide. A significant negative correlation was observed between the Lct/NAA ratio and VR (r = - 0.709, p < 0.0001). These results suggest that lactate levels and VR are closely related in regions outside areas of chronic cerebral infarction.     

Solid‐state NMR analyses of the crystalline–noncrystalline structure and its thermal changes for ethylene ionomers

The crystalline–noncrystalline structure and its structural changes from thermal treatments for ethylene ionomers have been investigated with solid‐state ¹³C and ²³Na NMR spectroscopy. ¹³C spin–lattice relaxation time (T_1C) measurements reveal that as‐received ethylene ionomers have much enhanced molecular mobility in the crystalline region in comparison with conventional polyethylene samples. By appropriate annealing, however, polyethylene‐like morphological features reflecting T_1C behavior can also be observed. ¹³C spin–spin relaxation time (T_2C) measurements for the noncrystalline region reveal the existence of two components with different T_2C values, and these two components have been assigned to the crystalline–amorphous interfacial and rubbery–amorphous components. These results indicate that the structure of the major part of the noncrystalline region in the ethylene ionomers is similar to that of bulk‐crystallized polyethylene samples, regardless of possible ionic aggregates. The origin of the lower temperature endothermic peak in the heating process of the differential scanning calorimetry curve observed for the as‐received sample has also been examined somewhat in detail. As a result, it is proposed that the melting of smaller crystallites produced during storage at room temperature is the origin of the lower temperature peak. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1142–1153, 2002     

Potassium ion conduction in K2O·(5 − x)Ga2O3·xAl2O3

Potassium gallate in which gallium ions are partially substituted by aluminium, K₂O·(5 ? x)Ga₂O₃·xAl₂O₃, has been prepared by sintering a mixture of K₂CO₃, Ga₂O₃, Al₂O₃ at 1500°C. It was found from X-ray diffraction that the gallate had the beta-alumina type β phase and that solid solutions were formed on substituting Ga by Al. The potassium gallate thus obtained was revealed to be a relatively high potassium ion conductor by a.c. conductivity and ionic transport number measurements. The potassium ion conductivity decreases monotonically with the aluminium content. In order to analyze the decreasing behavior of the conductivity isotherm, the slot width was calculated from the lattice parameters and the apparent porosity was evaluated using the apparent and theoretical densities. The change of the potassium ion conductivity with the substituted amount of aluminium was explained well by the variation of the slot width.