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71.
Salem Faham Tadashi J. Mizoguchi Elinor T. Adman Harry B. Gray John H. Richards D. C. Rees 《Journal of biological inorganic chemistry》1997,2(4):464-469
Replacement of the cysteine at position 112 of Pseudomonas aeruginosa azurin with an aspartic acid residue results in a mutant (Cys112Asp) protein that retains a strong copper-binding site. CuII(Cys112Asp) azurin can be reduced by excess [RuII(NH3)6]2+, resulting in a CuI protein with an electronic absorption spectrum very similar to that of wild-type CuI azurin. Cys112Asp azurin exhibits reversible interprotein electron-transfer reactivity with P. aeruginosa cytochrome c 551 (μ?=?0.1?M sodium phosphate (pH?7.0);E°(CuII/I)?=?180 mV vs NHE); this redox activity indicates that electrons can still enter and exit the protein through the partially solvent-exposed imidazole ring of His117. The structure of CuII(Cys112Asp) azurin at 2.4-Å resolution shows that the active-site copper is five coordinate: the pseudo-square base of the distorted square-pyramidal structure is defined by the imidazole Nδ atoms of His46 and His117 and the oxygen atoms of an asymmetrically-bound bidentate carboxylate group of Asp112; the apical position is occupied by the oxygen atom of the backbone carbonyl group of Gly45. The CuII–Asp112 interaction is distinguished by an approximately 1.2-Å displacement of the metal center from the plane defined by the Asp112 carboxylate group. 相似文献
72.
Kenji Hara Henneke Pangkey Kiyoshi Osatomi Keiko Yatsuda Atsushi Hagiwara Katsuyasu Tachibana Tadashi Ishihara 《Hydrobiologia》1997,358(1-3):89-94
We examined some characteristics of hydrolyticenzymes, especially -1,3-glucanase, to obtain theinformation of cell wall lytic enzymes forrotifers.Crude enzyme (ammonium sulfate fraction) of rotifershydrolyzed starch, -1,3-glucan, glycol chitinand CM-cellulose. Optimum pH for hydrolysis ofstarch and CM-cellulose was 6.5, and that for -1,3glucan and glycol chitin was pH 6.0. Pectic acid,xylan and agarose were not hydrolyzed at pH 3–10.-1,3 glucanase was purified about 73-fold from crudeenzyme by ion-exchange chromatography and gelfiltration. Optimum pH and temperature of the enzymewere 6 and 60 °C, respectively. The molecular weight ofthe enzyme was estimated about 260 kDa by gelfiltration. The enzyme was inhibited byHgCl2 and MnCl_2. 相似文献
73.
Relations Between the Extracellular Concentrations of Choline and Acetylcholine in Rat Striatum 总被引:2,自引:1,他引:1
Yasushi Ikarashi Akira Takahashi Hirohisa Ishimaru Tadashi Arai Yuji Maruyama 《Journal of neurochemistry》1997,69(3):1246-1251
Abstract: Changes in extracellular levels of acetylcholine (ACh) and choline (Ch) in the striatum of rats were examined by in vivo microdialysis after intraperitoneal injections of drugs. A dopamine D2 antagonist, sulpiride (20 mg/kg), and a muscarinic antagonist, atropine (3.5 mg/kg), increased ACh levels and decreased Ch levels. On the contrary, the D2 agonist (±)-2-( N -phenylethyl- N -propyl)amino-5-hydroxytetralin (N-434; 5 mg/kg) and an anesthetic, pentobarbital (50 mg/kg), decreased ACh levels and increased Ch levels. Perfusion of 10 µ M hemicholinium-3 (HC-3), a Ch uptake inhibitor, through the striatum induced a complete inhibition of ACh release and increased Ch levels in all drug-treated groups. The degree of relative increase in the level of Ch induced by HC-3 differed among the drug-pretreated groups; compared with the control group, the relative increase was larger in the sulpiride- and atropine-treated groups and smaller in the N-434 and pentobarbital-treated groups. Thus, we demonstrated reciprocal relations between extracellular concentrations of Ch and ACh after treatments by drugs. The data suggest that in the striatum, which is rich in cholinergic innervation, the extracellular Ch concentration is to a large extent determined by activity of the cholinergic transmission reflected in high-affinity choline uptake. 相似文献
74.
Application of bacterial magnetic particles as novel DNA carriers for ballistic transformation of a marine cyanobacterium 总被引:4,自引:0,他引:4
Haruko Takeyama Akira Yamazawa Chikashi Nakamura Tadashi Matsunaga 《Biotechnology Techniques》1995,9(5):355-360
Summary Bacterial magnetite particles (BMPs) of 50 to 100nm diam were used as DNA carriers for the ballistic transformation of the marine cyanobacteriumSynechococcus. BMPs were bombarded into the cyanobacterial cells at several bombardment velocities using a particle gun. Successful transformation and gene expression were confirmed by Southern hybridization and CAT assay, respectively. The BMPs were also observed in the cyanobacterial cells by transmission electron microscopy. These results suggested that BMPs can be used as carriers for introducing DNA into bacterial cells. 相似文献
75.
A photomicrobial sensor consisting of immobilized Chlorella vulgaris and an oxygen electrode has been developed for selective determination of phosphate. When 40 mM phosphate was added to the sensor system, the photocurrent increased to a maximum under light irradiation with a response time of 1 min. The current increased with increasing phosphate concentration in the range 8–70 mM. Selectivity of the sensor was satisfactory. Good agreement was obtained between the phosphate concentrations in lake water determined by the photomicrobial sensor and by conventional colorimetry (correlation coefficient 0.96). 相似文献
76.
Matsunaga Tadashi Tomoda Ryuzo Matsuda Hidemi 《Applied microbiology and biotechnology》1984,19(6):404-408
Summary A photomicrobial electrode, which uses the photosynthetic bacteria Chromatium sp. in conjunction with a hydrogen electrode, was developed for the determination of sulphide. The response time of the photomicrobial electrode was 5–10 min. A linear relationship was obtained between the current of the electrode and the sodium sulphide concentration below 3.5 mM. The minimum detectable concentration of sodium sulphide was 0.4 mM. Selectivity of the sensor is satisfactory. A good agreement was obtained between the photomicrobial electrode and the ethylene blue method (correlation coefficient: 0.90). 相似文献
77.
H Nomura A Kitamura Y Tanigawa M Tsuchiya M Ueki O Sugimoto M Shimoyama 《Biochimica et biophysica acta》1984,781(1-2):112-120
We examined the fragmentation of DNA treated with N-methyl-N-nitrosourea under conditions in which Ca2+, Mg2+-dependent endonuclease is active. The molecular mass of DNA found in mouse liver slices treated with methylnitrosurea in the presence of Ca2+ plus Mg2+ was 4 X 10(5) Da. Similar results were obtained with a reconstituted system containing partially purified Ca2+, Mg2+-dependent endonuclease and methylnitrosurea-treated DNA. The enzyme extensively cleaved methylnitrosurea-treated DNA, compared with non-treated DNA. The methylnitrosurea-treated nuclear proteins obtained from mouse liver nuclei had no effect on the DNA fragmentation by the enzyme. Using closed-circular DNA treated with methylnitrosurea, the enzyme produced single-strand cuts in the DNA, as was seen in non-treated, closed-circular DNA, however, the rate of hydrolysis was increased. Ca2+, Mg2+-dependent endonuclease thus warrants further investigation, with regard to the precise mechanism of extensive degradation of DNA in cells treated with carcinogenic alkylating agents. 相似文献
78.
The three protein kinases of Lemna paucicostata that are separableby DEAE-Sephacel chromatography have been designated PI, PIIand PIII [Kato et al. (1983) Plant & Cell Physiol. 24: 841].The optimum pH for the PI and PII enzymes was 7.5 and for thePHI enzyme 7.0. The activities of these enzymes were stimulatedby divalent cations, the maximum stimulation being producedby 5 nw Mg2 $ for PI, by 3 mM Co2 $ for PII and by 1 mM Mn2$ for PIII. The cytokinins; benzyladenine, kinetin and zeatin,inhibited the activity of the PIII enzyme. The molecular weightsof the PI and PII enzymes did not change after incubation withcAMP even though their activities were regulated by this compound. (Received October 17, 1983; ) 相似文献
79.
Summary A family with five induced and seven spontaneous abortions and no live births is described. Four of the seven spontaneous abortuses were available for cytogenetic examination and three were successfully karyotyped. Their karyotypes were 46,XX; 46,XX/46,XX,t(2;2)(2p2p;2q2q); and 46,XY. The karyotypes of the parents were normal. The origin of the 2p/2p and 2p/2p translocation in one of the abortuses was assigned to an interhomologous whole-arm translocation in an early mitotic division in a conceptus with a 46,XX karyotype. 相似文献
80.