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101.
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A novel FAD-dependent glucose dehydrogenase (FAD-GDH) was found and its enzymatic property for glucose sensing was characterized. FAD-GDH oxidized glucose in the presence of some artificial electron acceptors, except for O2, and exhibited thermostability, high substrate specificity and a large Michaelis constant for glucose. FAD-GDH was applied to an amperometric glucose sensor with Fe(CN)6(3-) as a soluble mediator. The use of a relatively high concentration of Fe(CN)6(3-) resulted in a good linearity between the current response and the glucose concentration, taking into account a large Michaelis constant for Fe(CN)6(3-). The glucose sensor was completely insensitive to O2 and responded linearly to glucose up to 30 mM. Compared to glucose, the response to other saccharides was negligible. The sensor can be stored at room temperature in a desiccator for at least one month without any change in the response or activity.  相似文献   
103.
Escherichia coli DnaA, an AAA+ superfamily protein, initiates chromosomal replication in an ATP-binding-dependent manner. Although DnaA has conserved Walker A/B motifs, it binds adenine nucleotides 10- to 100-fold more tightly than do many other AAA+ proteins. This study shows that the DnaA Asp-269 residue, located in the sensor 1 motif, plays a specific role in supporting high-affinity ATP/ADP binding. The affinity of the DnaA D269A mutant for ATP/ADP is at least 10- to 100-fold reduced compared with that of the wild-type and DnaA R270A proteins. In contrast, the abilities of DnaA D269A to bind a typical DnaA box, unwind oriC duplex in the presence of elevated concentrations of ATP, load DnaB onto DNA and support minichromosomal replication in a reconstituted system are retained. Whereas the acidic Asp residue is highly conserved among eubacterial DnaA homologues, the corresponding residue in many other AAA+ proteins is Asn/Thr and in some AAA+ proteins these neutral residues are essential for ATP hydrolysis but not ATP binding. As the intrinsic ATPase activity of DnaA is extremely weak, this study reveals a novel and specific function for the sensor 1 motif in tight ATP/ADP binding, one that depends on the alternate key residue Asp.  相似文献   
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We assessed sexual variation in food quality and gut macrostructure in adult male and pregnant female sika deer, Cervus nippon (Temminck, 1838), in Japan during winter. These variations might have important implications relative to sexual differences in habitat use, forage acquisition, and digestive strategy. According to the sexual dimorphism-body size hypothesis the larger males would feed on poorer forage and have heavier stomach contents and heavier intestine contents and longer intestines than smaller females. However, the food quality in rumen contents of males was higher than, or at least similar with, that of pregnant females. In correspondence to food quality, the relative weights of stomach contents and intestines with contents, the relative lengths of intestines to the lengths of body and total intestines in pregnant females were similar to adult males. The relative weights of omasum and abomasum tissues in pregnant females were greater than in males. Our findings suggest sexual differences in feeding strategy in sika deer in Japan during winter. To meet greater nutritional demands of high metabolic rate and gestation, pregnant females seemed to maintain a greater volume of digesta in guts and had more stomach tissues than expected by the sexual dimorphism-body size hypothesis to compensate for poorer forage quality.  相似文献   
106.
Homology based PCRs with degenerate primers designed from the conserved sequences among the known oxidosqualene cylases (OSCs) have resulted in cloning of a triterpene synthase (KcMS) from the young roots of Kandelia candel (L.) Druce (Rhizophoraceae). KcMS consists of a 2286 bp open reading frame, which codes for 761 amino acids. The deduced amino acid sequence showed 79% homology to a lupeol synthase from Ricinus communis suggesting it to be a lupeol synthase of K. candel. KcMS was expressed in a lanosterol synthase deficient yeast with the expression vector pYES2 under the control of GAL1 promoter. GC-MS analysis showed that the transformant accumulated a mixture of lupeol, beta-amyrin and alpha-amyrin in a 2:1:1 ratio, indicating that KcMS encodes a multifunctional triterpene synthase, although it showed high sequence homology to a R. communis lupeol synthase. This is the first OSC cloning from mangrove tree species.  相似文献   
107.
Ascorbate (vitamin C) is a potent antioxidant protecting plants against oxidative damage imposed by environmental stresses such as ozone and drought. Dehydroascorbate reductase (DHAR; EC 1.8.5.1) is one of the two important enzymes functioning in the regeneration of ascorbate (AsA). To examine the protective role of DHAR against oxidative stress, we developed transgenic tobacco plants overexpressing cytosolic DHAR gene from Arabidopsis thaliana . Incorporation of the transgene in the genome of tobacco plants was confirmed by polymerase chain reaction and Southern blot analysis, and its expression was confirmed by Northern and Western blot analyses. These transgenic plants exhibited 2.3–3.1 folds higher DHAR activity and 1.9–2.1 folds higher level of reduced AsA compared with non-transformed control plants. The transgenic plants showed maintained redox status of AsA and exhibited an enhanced tolerance to ozone, drought, salt, and polyethylene glycol stresses in terms of higher net photosynthesis. In this study, we report for the first time that the elevation of AsA level by targeting DHAR overexpression in cytosol properly provides a significantly enhanced oxidative stress tolerance imposed by drought and salt.  相似文献   
108.
A methanogenic bioreactor that utilized wastepaper was developed and operated at 55 degrees C. Microbial community structure analysis showed the presence of a group of clostridia that specifically occurred during the period of high fermentation efficiency. To isolate the effective cellulose digester, the sludge that exhibited high fermentation efficiency was inoculated into a synthetic medium that contained cellulose powder as the sole carbon source and was successively cultivated. A comprehensive 16S rRNA gene sequencing study revealed that the enriched culture contained various clostridia that had diverse phylogenetic positions. The microorganisms were further enriched by successive cultivation with filter paper as the substrate, as well as the bait carrier. A resultant isolate, strain EBR45 (= Clostridium sp. strain NBRC101661), was a new member of the order Clostridiales phylogenetically and physiologically related to Clostridium thermocellum and Clostridium straminisolvens. Specific PCR-based monitoring demonstrated that strain EBR45 specifically occurred during the high fermentation efficiency period in the original methanogenic sludge. Strain EBR45 effectively digested office paper in its pure cultivation system with a synthetic medium.  相似文献   
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Fifty-eight curcumin analogues were prepared and evaluated for in vitro cytotoxicity against a panel of human tumor cell lines. Compound was the most potent analogue against several cell lines, including HOS (bone cancer) and 1A9 (breast cancer), with ED50 values of 0.97 and <0.63 microg/mL, respectively.  相似文献   
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