Tokyo University of Science

About: Tokyo University of Science is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Thin film & Enantioselective synthesis. The organization has 15800 authors who have published 24147 publications receiving 438081 citations. The organization is also known as: Tōkyō Rika Daigaku & Science University of Tokyo.

Cytosolic dehydroascorbate reductase is important for ozone tolerance in Arabidopsis thaliana.

Abstract: ;Dehydroascorbate reductase (DHAR) is a key component of the ascorbate recycling system. Three functional DHAR genes are encoded in the Arabidopsis genome. Ozone exposure increased the expression of the cytosolic DHAR (cytDHAR) gene alone. We characterized an Arabidopsis mutant with a deficient cytDHAR. The mutant completely lacked cytDHAR activity and was highly ozone sensitive. The amounts of total ascorbate and glutathione were similar in both lines, but the amount of apoplastic ascorbate in the mutant was 61.5% lower. These results indicate that the apoplastic ascorbate, which is generated through the reduction of DHA by cytDHAR, is important for ozone tolerance.

Site-specific DNA methylation by a complex of PU.1 and Dnmt3a/b.

Abstract: The Ets transcription factor PU.1 is a hematopoietic master regulator essential for the development of myeloid and B-cell lineages. As we previously reported, PU.1 sometimes represses transcription on forming a complex with mSin3A-histone deacetyl transferase-MeCP2. Here, we show an interaction between PU.1 and DNA methyltransferases, DNA methyltransferase (Dnmt)3a and Dnmt3b (Dnmt3s). Glutathione-S-transferase pulldown assay revealed that PU.1 directly interacted with the ATRX domain of Dnmt3s through the ETS domain. Dnmt3s repressed the transcriptional activity of PU.1 on a reporter construct with trimerized PU.1-binding sites. The repression was recovered by addition of 5-aza-deoxycitidine, a DNA methyltransferase inhibitor, but not trichostatin A, a histone deacetylase inhibitor. Bisulfite sequence analysis revealed that several CpG sites in the promoter region neighboring the PU.1-binding sites were methylated when Dnmt3s were coexpressed with PU.1. We also showed that the CpG sites in the p16(INK4A) promoter were methylated by overexpression of PU.1 in NIH3T3 cells, accompanied by a downregulation of p16(INK4A) gene expression. These results suggest that PU.1 may downregulate its target genes through an epigenetic modification such as DNA methylation.

Synthesis and surface properties of anionic gemini surfactants with amide groups.

Abstract: Novel anionic gemini surfactants, 1,2-bis(N-beta-carboxypropanoyl-N-alkylamino)ethane (2CnenAm; n is hydrocarbon chain length of 6, 8, 10, 12, or 14), with two hydrocarbon chains, two carboxylate groups, and two amide groups, were synthesized by three-step reactions. Their solution properties were characterized by equilibrium and dynamic surface tension, steady-state fluorescence spectroscopy of pyrene, and dynamic light-scattering techniques. The surface tension measurements of 2CnenAm give low critical micelle concentrations (cmc), great efficiency in lowering the surface tension, and strong adsorption at air/water interface. Gemini surfactants behave normally with the logarithm of cmc decrease linearly with the chain length. In addition, adsorption and micellization behavior of 2CnenAm was estimated by parameter of pC20, cmc/C20, and standard free energy (DeltaG(0)mic and DeltaG(0)ads); they are significantly influenced by hydrocarbon chain length, and the adsorption is promoted more than the micellization as chain length becomes longer. The results of dynamic light-scattering and fluorescence quenching indicate that small micelles of 2CnenAm are observed at the concentrations above the cmc, and further large particles are also seen. Further, from the dynamic surface tension measurements, it is found that the shorter hydrocarbon chain length of 2CnenAm, the faster the rate of decrease of surface tension.

Determination of modulation of ligand properties of synthetic complex-type biantennary N-glycans by introduction of bisecting GlcNAc in silico, in vitro and in vivo.

Abstract: We have investigated the consequences of introducing a bisecting GlcNAc moiety into biantennary N-glycans. Computational analysis of glycan conformation with prolonged simulation periods in vacuo and in a solvent box revealed two main effects: backfolding of the α1–6 arm and stacking of the bisecting GlcNAc and the neighboring Man/GlcNAc residues of both antennae. Chemoenzymatic synthesis produced the bisecting biantennary decasaccharide N-glycan and its α2–3(6)-sialylated variants. They were conjugated to BSA to probe the ligand properties of N-glycans with bisecting GlcNAc. To assess affinity alterations in glycan binding to receptors, testing was performed with purified lectins, cultured cells, tissue sections and animals. The panel of lectins, including an adhesion/growth-regulatory galectin, revealed up to a sixfold difference in affinity constants for these neoglycoproteins relative to data on the unsubstituted glycans reported previously [Andre, S., Unverzagt, C., Kojima, S., Dong, X., Fink, C., Kayser, K. & Gabius, H.-J. (1997) Bioconjugate Chem. 8, 845–855]. The enhanced affinity for galectin-1 is in accord with the increased percentage of cell positivity in cytofluorimetric and histochemical analysis of carbohydrate-dependent binding of labeled neoglycoproteins to cultured tumor cells and routinely processed lung cancer sections. Intravenous injection of iodinated neoglycoproteins carrying galactose-terminated N-glycans into mice revealed the highest uptake in liver and spleen for the bisecting compound compared with the unsubstituted or core-fucosylated N-glycans. Thus, this substitution modulates ligand properties in interactions with lectins, a key finding of this report. Synthetic glycan tailoring provides a versatile approach to the preparation of newly substituted glycans with favorable ligand properties for medical applications.