No abstract

To construct yeast strains showing tolerance to high salt concentration stress, we analyzed the transcriptional response to high NaCl concentration stress in the yeast Saccharomyces cerevisiae using DNA microarray and compared between two yeast strains, a laboratory strain and a brewing one, which is known as a stress-tolerant strain. Gene expression dynamically changed following the addition of NaCl in both yeast strains, but the degree of change in the gene expression level in the laboratory strain was larger than that in the brewing strain. The response of gene expression to the low NaCl concentration stress was faster than that to the high NaCl concentration stress in both strains. Expressions of the genes encoding enzymes involved in carbohydrate metabolism and energy production in both strains or amino acid metabolism in the brewing strain were increased under high NaCl concentration conditions. Moreover, the genes encoding sodium ion efflux pump and copper metallothionein proteins were more highly expressed in the brewing strain than in the laboratory strain. According to the results of transcriptome analysis, candidate genes for the creation of stress-tolerant strain were selected, and the effect of overexpression of candidate genes on the tolerance to high NaCl concentration stress was evaluated. Overexpression of the GPD1 gene encoding glycerol-3-phosphate dehydrogenase, ENA1 encoding sodium ion efflux protein, and CUP1 encoding copper metallothionein conferred high salt stress tolerance to yeast cells, and our selection of candidate genes for the creation of stress-tolerant yeast strains based on the transcriptome data was validated.

A theoretical model, based on the bond-polarizability concept, js presented for the calculation of the Raman scattering intensities for crystals. The bonds in a unit cell are classified into groups in which the individual bond Raman polarizabihties are equivalent. The Raman polarizability of the crystals is expressed as the sum of the product of the bond Raman polarizability and the relative displacement of the end atoms linked by the bond. The theory is applied to the SiC polytypes. The calculated Raman intensity profiles reproduce qualitatively the observed Raman spectra of the folded modes which arise from TAand TO-phonon branches along the c direction.

An optical-capacitance-transient spectroscopy (O-CTS) method was used to characterize defects in epitaxial 6H-SiC. The O-CTS measurements enable us to estimate the optical ionization energy and the optical cross section of these defects. By the deep level transient spectroscopy (DLTS), three peaks were observed, and two of them were identified as E2 and R centers which have been previously reported. We measured the optical cross section for both the centers. By fitting the experimental data with theoretical curves for the optical cross section, we obtained optical ionization energy of 1.58 eV for the R center and 1.0 eV for the E2 center. From the DLTS measurements, the thermal activation energy of the R center is 1.30 eV and that of the E2 center is 0.43 eV. From these results and the previously reported capture energy barrier, the Franck–Condon shift, dFC is estimated to be 0.28 eV for the R center and 0.62 eV for the E2 center.

Raman scattering measurements have been made to determine the elastic deformation in ZnTe-ZnSe strained-layer superlattices grown by hotwall epitaxy. Both ZnSe- and ZnTe-like modes have been observed, which confirms the formation of a superlattice in the multilayer system having a large lattice mismatch between host layers. We observe that the frequencies of the ZnSe-like longitudinal and transverse phonon modes vary strikingly with the relative thickness of ZnTe and ZnSe layers. This effect is fully accounted for by uniform misfit strains which accommodate the lattice mismatch of the host.