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Biomedical subjects

I Okura

Publications and source records attributed to I Okura.

At least 19 recordsLinked to original sources
PubMed2001

Photoinduced hydrogen evolution with peptide dendrimer-multi-Zn(II)-porphyrin, viologen, and hydrogenase.

To construct an artificial photosynthetic system, multi-Zn(II)-mesoporphyrins in peptide dendrimers were equipped as a photosensitizer of photoinduced hydrogen evolution in a four-component system (electron donor, photosensitizer, electron carrier, and catalyst), so that hydrogen was evolved effectively by the dendrimer architecture, for the first time. The hydrogen evolution activity was correlated to the photoreduction ability of viologen by the Zn-porphyrin-peptide dendrimers. Additionally, using positively charged methyl-viologen as an electron carrier, the photoinduced hydrogen evolution function with the positively charged peptide dendrimer was superior to that with the negatively charged peptide dendrimer, despite that the positive dendrimer did not strongly bind the positively charged methyl-viologen with the electrostatic interaction. By contrast, when zwitterionic propylviologen sulfonate was used, photoreduction and hydrogen evolution properties were identical between the positively and the negatively charged dendrimers. These results demonstrated that the dynamic interaction between the positive dendrimer and methyl-viologen was preferable for the photoreduction and hydrogen evolution, and that the three-dimensional assembly of Zn(II)-mesoporphyrins using the peptide dendrimers was effective as a photosensitizer in the artificial photosynthesis.

Amino Acid Sequence↗
PubMed2001

Conversion of ammonia to dinitrogen in wastewater by Nitrosomonas europaea.

Because Nitrosomonas europaea contains ammonia-oxidizing enzyme, nitrite reductase, and nitrous oxide reductase, the conversion of ammonia to dinitrogen was tried with different reaction conditions. In aerobic reaction conditions, ammonium was converted to nitrite (NO2-), while under oxygen-limiting or oxygen-free conditions, NO2(-)-N formed from ammonia oxidation by N. europaea was reduced to N2O and dinitrogen with 22% conversion. During denitrification, optimal pH for the production of N2O and dinitrogen was found to be 7.0-8.0. Dinitrogen was not produced in acidic pH <7.0. A low partial oxygen pressure as well as oxygen-free conditions are favorable for high production of dinitrogen.

Ammonia↗
PubMed2000

Preparation of a water-soluble fluorinated zinc phthalocyanine and its effect for photodynamic therapy.

An amphiphilic fluorinated phthalocyanine, zinc tetracarboxyoctafluorophthalocyanine (ZnC4F8Pc) was synthesized and characterized. Its photodynamic efficiency for HeLa cells was compared with hydrophilic zinc octacarboxyphthalocyanine (ZnC8Pc) and hydrophobic zinc hexadecafluorophthalocyanine (ZnF16Pc). ZnC4F8Pc had a remarkable photodynamic effect among the phthalocyanines used. The effect is apparently caused by the fact that ZnC4F8Pc is mainly accumulated in the hydrophobic lipid membrane and is in the photoactive monomer form in HeLa cells.

Fluorine↗
PubMed1999

Removal of disperse dyes by the fungus Cunninghamella polymorpha.

A disperse dye-removing fungus, Cunninghamella polymorpha, was isolated from soil. C. polymorpha efficiently removed an average 93% of 17 tested disperse dyes in 120 h, and 90% of C. I. Disperse Blue 60 was removed even at a high concentration of 500 mg/l. The dye removal was due to the sorption of dye to the fungal cells.

Journal Article↗
PubMed1999

Relationship between the effect of interferon therapy and the change of hepatitis C virus non-structural 5B gene.

BACKGROUND: Hepatitis C virus (HCV)-RNA titre has been regarded as a factor affecting the response to interferon (IFN) therapy of patients with chronic hepatitis C (CHC). The focus of our study is the investigation of the nucleotide sequence of HCV-RNA NS5B, which may code RNA-dependent RNA polymerase and NS5A in the sera of 33 patients with CHC prior to IFN therapy. METHODS: Hepatitis C virus genotype and HCV-RNA titre were examined by polymerase chain reaction (PCR) and competitive reverse transcriptase-PCR. RESULTS: The sequence for HCV-RNA NS5B (nt 8331-8600 in 1b and 8410-8679 in 2a) was determined by direct sequencing. The changes of the predicted amino acids in the genotype-specific sites of HCV-J, HCV-BK, HC-J4/83, HCV-JT, HCV-N, HC-J6 and HCV-K2a were examined, and the mutation was defined when changes of amino acids in sites specific to different reported genotypes were revealed. The mutations were observed in 6/19 (32%) in genotype 1b and 9/14 (64%) in 2a. In the 1b group, complete response (CR) was achieved in 5/6 of the mutant and in 2/13 of the wild type groups (P < 0.05). No relationship was observed between IFN effectiveness and HCV-RNA titre in the 1b wild type group. In the 2a group, CR was achieved in 4/9 of the mutant and in 4/5 of the wild type groups. An inverse relationship between IFN responsiveness and HCV-RNA titre was apparent in 1b mutant, 2a wild and 2a mutant. CONCLUSIONS: These data suggest the possible relationship between changes in the HCV-NS5B gene and the effect of IFN therapy in CHC patients with genotype 1b.

Amino Acid Sequence↗
PubMed1998

Effect of side chain location in (2-aminoethyl)-aminomethyl-2-phenylquinolines as antitumor agents.

Three new derivatives of 2-phenylquinoline having an (2-aminoethyl)aminomethyl group in 7-, 6-, or 4'- (para position of 2-phenyl ring) positions of aromatic system have been prepared. The antitumor activity of these compounds together with 8- or 4- substituted isomers against the HeLa cell is in the order of 8- > 7- > 4- approximately 6- approximately 4'- substituted ones, which is almost in good agreement with that of DNA-binding ability evaluated by means of DNA-titration of UV-VIS spectra, DNA melting experiment, and ethidium displacement assay. Two representative compounds (8- and 4- isomers) are confirmed to have an ability to intercalate into double stranded DNA by topoisomerase I superhelix unwinding assay.

Animals↗
PubMed1998

Properties of the membranes containing the particulate methane monooxygenase from Methylosinus trichosporium OB3b.

The particulate methane monooxygenase (pMMO) from Methylosinus trichosporium OB3b was partially purified and characterized by measuring the effects of reducing agents and additives, and the stability of pMMO was studied. Duroquinol was a suitable reducing agent, and pMMO was stabilized by bovine serum albumin (BSA). Among the additives, the copper (II) ion stimulated pMMO at low concentration and inhibited at high concentration. The optimum conditions for pMMO activity were as follows: 45 degrees C, pH 6.5 and 55 mM 3-morpholinopropanesulfonic acid (MOPS) buffer, and the rate of propene epoxide formation was 13.6 nmol min-1 mg-1 protein. ESR spectra indicate that the copper cluster in the membrane fraction is reduced by duroquinol and oxidized by dioxygen. The result suggests that the copper cluster is contained in the active site of pMMO.

Animals↗
PubMed1996

Protection against Fas/APO-1- and tumor necrosis factor-mediated cell death by a novel protein, sentrin.

Fas/APO-1 and TNF receptor 1 share a common signaling motif in their cytoplasmic tail called the "death domain." Using the death domain as bait in the yeast two-hybrid system, several death domain-containing proteins that participate in cell death signaling have been identified. Here we report the isolation of a novel protein, sentrin, which interacts with Fas/APO-1 and TNF receptor 1 but not with FADD/MORT1 or CD40. Two-hybrid interaction assays reveal that sentrin associates only with the signal-competent forms of Fas/APO-1 or TNF receptor 1 death domains. Sentrin is a novel protein of 101 amino acids with homology to ubiquitin, Nedd8, and a Saccharomyces cerevisiae protein, Smt3. When overexpressed, sentrin provides protection against both anti-Fas/APO-1 and TNF-induced cell death.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Synthesis of alanine and leucine by reductive amination of 2-oxoic acid with combination of hydrogenase and dehydrogenase.

Alanine synthesis by reductive amination of pyruvate was performed by the combination of NADH regeneration system and alanine dehydrogenase (AlaDH). The conversion of pyruvate to alanine was 99% after 1 h. Leucine synthesis was also carried out by the combination of NADH regeneration system and leucine dehydrogenase (LeuDH). The conversion of 4-methyl-2-oxovalerate to leucine was 60% after 1.5 h.

Alanine↗
PubMed1995

Kinetics of calcium release by immunoaffinity-purified inositol 1,4,5-trisphosphate receptor in reconstituted lipid vesicles.

The kinetics of inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ release of the immunoaffinity-purified IP3 receptor (IP3R), reconstituted into lipid vesicles, was investigated using the fluorescent Ca2+ indicator fluo-3. IP3R was purified from mouse cerebellar microsomal fraction by using an immunoaffinity column conjugated with an anti-IP3R type 1 (IP3R1) antibody. The immunoblotting analysis using monoclonal antibodies against each IP3R type showed that the purified IP3R is almost homogeneous, composed of IP3R1. Ca2+ efflux from the proteoliposomes was monitored as fluorescence changes of 10 microM fluo-3, whose concentration was high enough to buffer released Ca2+ and to keep deviations of extravesicular free Ca2+ concentration within 30 nM, excluding the possibility of Ca(2+)-mediated regulation of IP3-induced Ca2+ release. We also examined IP3-induced Ca2+ release using 1 microM fluo-3, where the deviations of free Ca2+ concentration were within 300 nM. At both fluo-3 concentrations, IP3-induced Ca2+ release showed similar kinetic properties, i.e. little Ca2+ regulation of Ca2+ release was observed in this system. IP3-induced Ca2+ release of the purified IP3R exhibited positive cooperativity; the Hill coefficient was 1.8 +/- 0.1. The half-maximal initial rate for Ca2+ release occurred at 100 nM IP3. At the submaximal concentrations of IP3, the purified IP3R showed quantal Ca2+ release, indicating that a single type of IP3R is capable of producing the phenomenon of quantal Ca2+ of release. The profiles of the IP3-induced Ca2+ release of the purified IP3R were found to be biexponential with the fast and slow rate constants (k(fast) = 0.3 approximately 0.7 s-1, k(slow) = 0.03 approximately 0.07 s-1), indicating that IP3R has two states to release CA2+. The amount of released Ca2+ by the slow phase was constant over the range of 10-5000 nM IP3 concentrations, whereas that by the fast phase increased in proportion to added IP3. This provides evidence to support the view that the fast phase of Ca2+ release is mediated by the low affinity state and the slow phase by the high affinity state of the IP3R. This also suggests that the fast component of Ca2+ release is responsible for the process of quantal Ca2+ release.

Animals↗
PubMed1995

Adenophostin-medicated quantal Ca2+ release in the purified and reconstituted inositol 1,4,5-trisphosphate receptor type 1.

Kinetics of Ca2+ release by adenophostin, a novel agonist of inositol 1,4,5-trisphosphate (IP3) receptor, in the purified and reconstituted IP3 receptor type 1 (IP3R1) was investigated using the fluorescent Ca2+ indicator fluo-3. Submaximal concentrations of adenophostin caused quantal Ca2+ release from the purified IP3R1 as IP3 did. Adenophostin-induced Ca2+ release by the purified IP3R1 exhibited a high positive cooperativity (nH = 3.9 +/- 0.2, EC50 = 11 nM), whereas the IP3-induced Ca2+ release exhibited a moderate one (nH = 1.8 +/- 0.1, EC50 = 100 nM). Inhibition of [3H]IP3 binding to the purified IP3R1 by adenophostin exhibited a positive cooperativity (nH = 1.9, Ki = 10 nM), whereas IP3 did not (nH = 1.1, Ki = 41 nM).

Adenosine↗
PubMed1994

Cloning and expression of the gene encoding the 7Fe type ferredoxin from a thermophilic hydrogen oxidizing bacterium, Bacillus schlegelii.

The structural gene (fdxA) coding for a 7Fe type ferredoxin of a thermophilic hydrogen oxidizing bacterium Bacillus schlegelii has been cloned and sequenced. The fdxA coding region is 231 nucleotides which codes for a 77 amino acids protein with the molecular weight of 8,744 except for iron-sulfur clusters. The fdxA gene has been expressed in E. coli to obtain the recombinant ferredoxin. The recombinant ferredoxin have shown the identical properties to the native one for absorption spectra, and SDS-PAGE.

Amino Acid Sequence↗
PubMed1992

Purification and characterization of a 7Fe ferredoxin from a thermophilic hydrogen-oxidizing bacterium, Bacillus schlegelii.

A ferredoxin (Fd) was purified from a thermophilic hydrogen-oxidizing bacterium, Bacillus schlegelii. This ferredoxin was a monomer with apparent molecular weight of 13,000 and contained 7 mol Fe/mol ferredoxin. The oxidized ferredoxin showed the characteristic EPR spectrum for [3Fe-4S]1+ (1.2 spin/mol Fd). This signal disappeared upon reduction with dithionite and new signals due to [3Fe-4S]0 and [4Fe-4S]1+ (0.7 spin/mol Fd) appeared. The quantitation of EPR signals and the iron content reveal that B. schlegelii ferredoxin contains one [3Fe-4S]1+/0 and one [4Fe-4S]2+/1+ cluster. The ferredoxin has the characteristic distribution of cysteines (-Cys8-X7-Cys16-X3-Cys20-Pro-) for 7Fe ferredoxins in the N-terminus.

Amino Acid Sequence↗
PubMed1986

Application of hydrogenase for photoinduced hydrogen evolution.

Various attempts have been made to develop suitable redox systems for the photochemical utilization of solar energy. Recent work has shown that the three component systems containing a photosensitizer, an electron donor, and an electron acceptor can be used to evolve hydrogen when a suitable catalyst is present. The reactions are quite general and have been demonstrated for a wide range of photosensitizers and electron carriers. Hydrogenase or colloidal platinum are widely used as catalysts, for they can catalyze the reduction of protons in the presence of a suitable electron donating agent such as reduced methylviologen. Some properties of these components and the efficiency of the photoinduced hydrogen evolution are discussed.

Chemical Phenomena↗