Biochemical characterization of photosystem I complexes having different subunit compositions of fucoxanthin chlorophyll a/c-binding proteins in the diatom Chaetoceros gracilis

Photosynthesis Research - Diatoms are dominant phytoplankton in aquatic environments and have unique light-harvesting apparatus, fucoxanthin chlorophyll a/c-binding protein (FCP). Diatom...     

Regulation of excitation energy in Nannochloropsis photosystem II

Photosynthesis Research - Recently, we isolated a complex consisting of photosystem II (PSII) and light-harvesting complexes (LHCs) from Nannochloropsis granulata (Umetani et al. Photosynth Res...     

Computational chemical analysis of Ru(II)‐Pheox–catalyzed highly enantioselective intramolecular cyclopropanation reactions

Computational chemical analysis of Ru(II)‐Pheox–catalyzed highly enantioselective intramolecular cyclopropanation reactions was performed using density functional theory (DFT). In this study, cyclopropane ring–fused γ‐lactones, which are 5.8 kcal/mol more stable than the corresponding minor enantiomer, are obtained as the major product. The results of the calculations suggest that the enantioselectivity of the Ru(II)‐Pheox–catalyzed intramolecular cyclopropanation reaction is affected by the energy differences between the starting structures 5l and 5i . The reaction pathway was found to be a stepwise mechanism that proceeds through the formation of a metallacyclobutane intermediate. This is the first example of a computational chemical analysis of enantioselective control in an intramolecular carbene‐transfer reaction using C₁‐symmetric catalysts.     

Differential regulation of immediate early gene expression in preadipocyte cells through multiple signaling pathways

Using digoxigenin (DIG)-based differential hybridization, a series of immediate early genes (IEG) was identified following the adipogenic stimulation in 3T3-L1 preadipocyte cells. Most of the known IEGs were identified as well as new members such as zf9 and Stra13. To delineate possible signaling pathways accounting for these gene expression, a subset of specific kinase inhibitors, SB203580, PD98059, rapamycin, LY294002, and Ro-32-0432, which inhibit p38 (HOG), MEK (MAPKK), S6 kinase, PI3 kinase, and protein kinase C (PKC), respectively, were employed. The IEGs were classified into three categories according to their susceptibility to the inhibitors. Expression of the first group (c-fos, jun-B, egr-1, tis11, tis21, thrombospondin-1, erp, thyroid hormone receptor [N-10], cyr61, and zf9) was mainly dependent on PKC and MEK pathways, while that of the second class (gene33 and tis10) exhibited an additional dependence on PI3 kinase pathways. The third one (Id-3, gly96, and Stra13) was characterized in that none of these inhibitors interfered with gene expression. Our results suggest that the induction of IEGs by the adipogenic stimuli is mediated by common as well as distinct signaling pathways.     

Metabolism of benzoquinone by yeast cells and oxidative characteristics of corresponding hydroquinone: application to highly sensitive measurement of yeast cell density by using benzoquinone and a chemiluminescent probe

The metabolic efficiency of seven derivatives of 1,4-benzoquinone (BQ) by yeast cells and the oxidative characteristics of the corresponding hydroquinones (HQs) were studied by electrochemical, spectrophotometric and chemiluminescent methods. The spectrophotometric method was based on the reduction of a tetrazolium salt to formazan dye during the autoxidation of HQs generated by yeast cells under alkaline conditions. The amounts of HQs detected directly by the electrochemical method did not agree with those calculated from the formazan dye obtained by the spectrophotometric method. A tetrazolium salt was reduced to a formazan dye by both the superoxide anion radical (O2-*) generated during the autoxidation of 2,3,5,6-tetramethyl-1,4-HQ and by HQ itself. Little formazan dye was formed, and hydrogen peroxide (H2O2) was then finally produced during the autoxidation of 1,4-HQ or 2-methyl-1,4-HQ. Formazan dye and H2O2 were generated at a certain ratio during the autoxidation of derivatives of dimethyl-1,4-HQ or 2,3,5-trimethyl-1,4-HQ. The analytical method based on chemiluminescence with lucigenin and 2,3,5,6-tetramethyl-1,4-BQ was applied to highly sensitive measurement of the yeast cell density. A linear relationship between the chemiluminescence intensity and viable cell density was obtained in the range of 1.2 x 10(3) - 4.8 x 10(4) cells/ml. The detection limit was 4.8 x 10(2) cells/ml.