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991.
Non-catalytic liquefaction of Japanese beech (Fagus crenata) wood in subcritical phenol was investigated using a batch-type reaction vessel. After samples were treated at 160 °C/0.9 MPa–350 °C/4.2 MPa for 3–30 min, they were fractionated into a phenol-soluble portion and phenol-insoluble residues. These residues were then analyzed for their chemical composition. Based on the obtained data, the kinetics for liquefaction was modeled using first-order reaction rate law. Subsequently, the liquefaction rate constants of the major cell wall components including cellulose, hemicellulose, and lignin were determined. The different kinetic mechanisms were found to exist for lignin and cellulose at two different temperature ranges, lower 160–290 °C and higher 310–350 °C, whereas for hemicellulose, it was only liquefied in the lower temperature range. Thus, the liquefaction behaviors of these major cell wall components highlighted hemicellulose to be the most susceptible to liquefaction, followed by lignin and cellulose. 相似文献
992.
993.
In an effort to develop selective MAO (monoamine oxidase) B inhibitors, structure based virtual screening was initiated on an in-house library. Top 10 HITS were synthesized and evaluated for MAO (A and B) inhibitory activity, both against human and rat enzymes. All the compounds were found selective, reversible and active in nM range (100 times more potent than selegeline) towards MAO-B. Outstanding co-relation between predicted and experimental Ki values were observed. 相似文献
994.
995.
Fibroblast growth factor-1, a member of the 3-fold symmetric β-trefoil fold, was subjected to a series of symmetric constraint mutations in a process termed “top-down symmetric deconstruction.” The mutations enforced a cumulative exact 3-fold symmetry upon symmetrically equivalent positions within the protein and were combined with a stability screen. This process culminated in a β-trefoil protein with exact 3-fold primary-structure symmetry that exhibited excellent folding and stability properties. Subsequent fragmentation of the repeating primary-structure motif yielded a 42-residue polypeptide capable of spontaneous assembly as a homotrimer, producing a thermostable β-trefoil architecture. The results show that despite pronounced reduction in sequence complexity, pure symmetry in the design of a foldable, thermostable β-trefoil fold is possible. The top-down symmetric deconstruction approach provides a novel alternative means to successfully identify a useful polypeptide “building block” for subsequent “bottom-up” de novo design of target protein architecture. 相似文献
996.
The effects of arsenite treatment on generation of reactive oxygen species, induction of oxidative stress, response of antioxidative
system, and synthesis of phytochelatins were investigated in two indica rice (Oryza sativa L.) cvs. Malviya-36 and Pant-12 grown in sand cultures for a period of 5–20 days. Arsenite (As2O3; 25 and 50 μM) treatment resulted in increased formation of superoxide anion (O2.−), elevated levels of H2O2 and thiobarbituric acid reactive substances, showing enhanced lipid peroxidation. An enhanced level of ascorbate (AA) and
glutathione (GSH) was observed irrespective of the variation in the level of dehydroascorbate (DHA) and oxidized glutathione
(GSSG) which in turn influenced redox ratios AA/DHA and GSH/GSSG. With progressive arsenite treatment, synthesis of total
acid soluble thiols and phytochelatins (PC) increased in the seedlings. Among antioxidative enzymes, the activities of superoxide
dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6), total ascorbate peroxidase (APX, EC 1.11.1.11), chloroplastic ascorbate peroxidase,
guaiacol peroxidase (EC 1.11.1.7), monodehydroascorbate reductase (EC 1.6.5.4), and glutathione reductase (EC 1.6.4.2) increased
in arsenite treated seedlings, while dehyroascorbate reductase (EC 1.8.5.1) activity declined initially during 5–10 days and
increased thereafter. Results suggest that arsenite treatment causes oxidative stress in rice seedlings, increases the levels
of many enzymatic and non-enzymatic antioxidants, and induces synthesis of thiols and PCs, which may serve as important components
in mitigating arsenite-induced oxidative damage. 相似文献
997.
Comet assay under neutral conditions allows detection of DNA double-strand breaks (DSBs), which has consequence to genome instability and carcinogenesis. The present study aims to validate the neutral Comet assay for genotoxicity assessment in Drosophila melanogaster (Oregon R(+)) with three well known DSBs inducers i.e. cyclophosphamide (CP), bleomycin (BLM), cisplatin (CPT) and subsequently its efficacy in detecting DSBs in the organism exposed to a well known environmental chemical, chromium [Cr(VI)]. Third instar larvae of D. melanogaster were fed different concentrations of BLM, CPT and CP (50.0-200.0μg/ml) or Cr(VI) (5.0-20.0μg/ml) mixed standard Drosophila food for 48h. Neutral Comet assay was performed in cells of mid gut and brain from control and treated larvae. Our results show a dose-dependent increase in the migration of DNA in cells of the exposed organisms. A comparison among DNA lesions per mole number of the test chemical in the exposed groups showed that both BLM and CPT induce more DSBs than CP. Interestingly, Cr(VI) at 20.0μg/ml was found to induce significantly increased (p<0.001) DSBs in the exposed organism as compared to the control. The study while validating neutral Comet assay in D. melanogaster suggests its use for in vivo assessment of environmental chemical induced DSBs. 相似文献
998.
Mutagen sensitive strains (mus) in Drosophila are known for their hypersensitivity to mutagens and environmental carcinogens. Accordingly, these mutants were grouped in pre- and post-replication repair pathways. However, studying mutants belonging to one particular repair pathway may not be adequate for examining chemical-induced genotoxicity when other repair pathways may neutralize its effect. To test whether both pre-and post-replication pathways are involved and effect of Cr(III)- and Cr(VI)-induced genotoxicity in absence or presence of others, we used double mutant approach in D. melanogaster. We observed DNA damage as evident by changes in Comet assay DNA migration in cells of larvae of Oregon R(+) and single mutants of pre- (mei-9, mus201 and mus210) and post- (mei-41, mus209 and mus309) replication repair pathways and also in double mutants of different combinations (pre-pre, pre-post and post-post replication repair) exposed to increasing concentrations of Cr(VI) (0.0, 5.0, 10.0 and 20.0 μg/ml) for 48 h. The damage was greater in pre-replication repair mutants after exposure to 5.0 μg/ml Cr(VI), while effects on Oregon R(+) and post replication repair mutants were insignificant. Post-replication repair mutants revealed significant DNA damage after exposure to 20.0 μg/ml Cr(VI). Further, double mutants generated in the above repair categories were examined for DNA damage following Cr(VI) exposure and a comparison of damage was studied between single and double mutants. Combinations of double mutants generated in the pre-pre replication repair pathways showed an indifferent interaction between the two mutants after Cr(VI) exposure while a synergistic interaction was evident in exposed post-post replication repair double mutants. Cr(III) (20.0 μg/ml) exposure to these strains did not induce any significant DNA damage in their cells. The study suggests that both pre- and post-replication pathways are affected in Drosophila by Cr(VI) leading to genotoxicity, which may have consequences for metal-induced carcinogenesis. 相似文献
999.
Mishra A Holmes WJ Liew S 《Plastic and reconstructive surgery》2011,127(6):2507-8; author reply 2508-9
1000.