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91.
Biologically active alkylated coumarins from Kayea assamica 总被引:2,自引:0,他引:2
Four coumarin derivatives, theraphins A (1), B (2), C (3), and D (4), along with three known xanthones, 2-hydroxyxanthone, 1,7-dihydroxyxanthone, and 5-hydroxy-1-methoxyxanthone, were isolated from the bark of Kayea assamica (Clusiaceae) native to Myanmar. Their structures were determined using spectroscopic and chemical techniques. The absolute configuration of 1 was established by the modified Mosher ester method. Theraphins A (1), B (2), and C (3) exhibited good cytotoxicity against Col2, KB, and LNCaP human cancer cell lines. Theraphin D (4) showed mild activity only against the KB cell line. The coumarins also exhibited mild antimalarial activities. 相似文献
92.
6(A),6(D)-Bis-(2-amino-2-carboxylethylthio)-6(A),6(D)-dideoxy-beta-cyclodextrin 1, a diamino acid derivative of beta-cyclodextrin, is synthesized and condensed with difunctionalized PEG comonomers to give linear, high molecular weight (M(w) over 50 kDa) beta-cyclodextrin-based polymers (2-4) with pendant functionality (carboxylate). 2-4 are all highly soluble in aqueous solutions (over 200 mg/mL). 20-O-trifluoroglycinylcamptothecin, 5a, and 20-O-trifluoroglycinylglycinylglycinylcamptothecin, 5b, are synthesized and conjugated to 2 to give polymer-camptothecin (CPT) prodrugs. The solubility of CPT is increased by more than three orders of magnitude when it is conjugated to 2. The rates of CPT release from the conjugates HGGG6 (high molecular weight polymer (M(w) 97 kDa), glyglygly linker and 6 wt % CPT loading) and HG6 (high MW polymer (M(w) 97 kDa), gly linker and 6 wt % CPT loading) in either mouse or human plasma are dramatically accelerated over the rates of pure hydrolysis at pH = 7.4, indicating the presence of enzymatic cleavage as a rate-determining step at this pH in the release of the CPT. The pH of aqueous solution has a large effect on hydrolysis rate of CPT from HGGG6 and HG6; the lower the pH, the slower the rate in the range at 4.1 相似文献
93.
The use of the fungus Aspergillus niger for the bioleaching of heavy metals from spent catalyst was investigated, with fluid catalytic cracking (FCC) catalyst as a model. Bioleaching was examined in batch cultures with the spent catalysts at various pulp densities (1-12%). Chemical leaching was also performed using mineral acids (sulphuric and nitric acids) and organic acids (citric, oxalic and gluconic acids), as well as a mixture of organic acids at the same concentrations as that biogenically produced. It was shown that bioleaching realised higher metal extraction than chemical leaching, with A. niger mobilizing Ni (9%), Fe (23%), Al (30%), V (36%) and Sb (64%) at 1% pulp density. Extraction efficiency generally decreased with increased pulp density. Compared with abiotic controls, bioleaching gave rise to higher metal extractions than leaching using fresh medium and cell-free spent medium. pH decreased during bioleaching, but remained relatively constant in both leaching using fresh medium and cell-free spent medium, thus indicating that the fungus played a role in effecting metal extraction from the spent catalyst. 相似文献
94.
Paenibacillus curdlanolyticus Strain B-6 Xylanolytic-Cellulolytic Enzyme System That Degrades Insoluble Polysaccharides
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A facultatively anaerobic bacterium, Paenibacillus curdlanolyticus B-6, isolated from an anaerobic digester produces an extracellular xylanolytic-cellulolytic enzyme system containing xylanase, β-xylosidase, arabinofuranosidase, acetyl esterase, mannanase, carboxymethyl cellulase (CMCase), avicelase, cellobiohydrolase, β-glucosidase, amylase, and chitinase when grown on xylan under aerobic conditions. During growth on xylan, the bacterial cells were found to adhere to xylan from the early exponential growth phase to the late stationary growth phase. Scanning electron microscopic analysis revealed the adhesion of cells to xylan. The crude enzyme preparation was found to be capable of binding to insoluble xylan and Avicel. The xylanolytic-cellulolytic enzyme system efficiently hydrolyzed insoluble xylan, Avicel, and corn hulls to soluble sugars that were exclusively xylose and glucose. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of a crude enzyme preparation exhibited at least 17 proteins, and zymograms revealed multiple xylanases and cellulases containing 12 xylanases and 9 CMCases. The cellulose-binding proteins, which are mainly in a multienzyme complex, were isolated from the crude enzyme preparation by affinity purification on cellulose. This showed nine proteins by SDS-PAGE and eight xylanases and six CMCases on zymograms. Sephacryl S-300 gel filtration showed that the cellulose-binding proteins consisted of two multienzyme complexes with molecular masses of 1,450 and 400 kDa. The results indicated that the xylanolytic-cellulolytic enzyme system of this bacterium exists as multienzyme complexes. 相似文献
95.
M Eisbacher L M Khachigian T H Khin M L Holmes B H Chong 《Cell growth & differentiation》2001,12(8):435-445
Glycoprotein IX is a megakaryocyte-specific gene crucial for adequate and functional expression of the Glycoprotein Ib-IX complex. This study used phorbol 12-myristate 13-acetate (PMA) and thrombopoietin (TPO)-induced differentiation of Dami and UT-7 cells, respectively, to investigate the regulation of inducible Glycoprotein IX expression during megakaryocyte differentiation. PMA and TPO were able to modulate GPIX expression at mRNA and protein levels. Transient transfection studies using nested 5'-deletions and mutations of the GPIX promoter demonstrated the absolute requirement of an inverted Ets site 5'-ACTTCCT-3' for inducible reporter gene expression. The upstream signaling events associated with PMA and TPO-inducible expression of GPIX were also investigated. The mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase inhibitor PD98059 inhibited both PMA and TPO-inducible reporter activity in a dose-dependent manner, whereas inhibition of p38/MAPK had no significant effect. The protein kinase C inhibitor GF109203X failed to inhibit TPO-activation of the GPIX promoter in UT-7 cells. This study demonstrates that inducible expression in response to either PMA or TPO is mediated through the Ets site in the proximal promoter of GPIX and is dependent upon the upstream activation of MAPK/extracellular signal-regulated kinase. 相似文献
96.
The antifouling (AF) properties of zinc oxide (ZnO) nanorod coated glass substrata were investigated in an out-door mesocosm experiment under natural sunlight (14:10 light: dark photoperiod) over a period of five days. The total bacterial density (a six-fold reduction) and viability (a three-fold reduction) was significantly reduced by nanocoatings in the presence of sunlight. In the absence of sunlight, coated and control substrata were colonized equally by bacteria. MiSeq Illumina sequencing of 16S rRNA genes revealed distinct bacterial communities on the nanocoated and control substrata in the presence and absence of light. Diatom communities also varied on nanocoated substrata in the presence and the absence of light. The observed AF activity of the ZnO nanocoatings is attributed to the formation of reactive oxygen species (ROS) through photocatalysis in the presence of sunlight. These nanocoatings are a significant step towards the production of an environmentally friendly AF coating that utilizes a sustainable supply of sunlight. 相似文献
97.
Rod W. King Masateru Shinozaki Atsushi Takimoto Khin Lay Swe 《Journal of plant research》1994,107(3):215-219
Dwarfing and sensitivity to the duration of a single inductive dark period for flowering ofPharbitis nil in F2 progeny of a cross between the tall strain Tendan, and the dwarf, Kidachi appear to be controlled by the alleles at two independent
loci. Progeny of a similar cross between the tall strain Violet and the dwarf Kidachi at F2 and F3 also showed single locus segregation for tall: dwarf plants. In this cross, differences in photoperiodic response could be
identified in F3 families but they were not simply inherited. There was some evidence of difficulties with classification of the F2 plants, but also, the flowering of the F1 between the two less sensitive strains Tendan and Violet indicated complex inheritance of their photoperiodic response. Complementary
dominant alleles at three independent loci may be necessary for flowering in even shorter dark periods with the sensitive
strain Kidachi.
The dwarf strain Kidachi has a reduced gibberellin (GA) content (Barendse and Lang 1972), it flowers in a short dark period
without terminal flowering, and it responds positively to GA application both for flowering and growth. However, since control
of dwarfing and photoperiodic sensitivity can be separated genetically, there is no strick link between the gibberellin responsiveness
of Kidachi for its growth and flowering. Despite the complexity of flowering genetics in Violet×Kidachi, a short-dark-period-sensitive,
terminal flowering and tall F7 line was obtained in a pedigree previously held heterozygous for the dwarf: tall character but not selected for flowering
time. Thus, flowering in a short dark period can also be obtained in the presence of the non-dwarfing allele from strain Violet,
again demonstrating genetic independence. 相似文献
98.
利用地面观测和单绳上树法初次对布龙自然保护区勐宋片区开展的附生维管植物调查表明:1)在6个样地77株宿主上(共调查96株乔木,占地约0.2ha),共有1 756株、丛个体,隶属14科47属103种;相比世界其他区域,物种丰富度处于旧世界热带水平区间,高于温带,但明显低于新世界热带水平;2)兰科植物为最丰富的类群(60%),其次为蕨类植物(24%),其他类群占16%;3)垂直分布特征研究表明,距地面10~ 15 m的中等高度带为物种最丰富的区间,约有51%的物种;0~5m高度带为个体数量最多的区间,共有约24%个体,揭示了除中等高度带以外的另一个重要附生生境;4)常见的绞杀型榕属植物未见,而半附生植物密脉鹅掌柴(Schefflera elliptica)和多蕊木(Tupidanthus calyptratus)数量较多. 相似文献
99.
Yael Litvak Khin K.Z. Mon Henry Nguyen Ganrea Chanthavixay Megan Liou Eric M. Velazquez Laura Kutter Monique A. Alcantara Mariana X. Byndloss Connor R. Tiffany Gregory T. Walker Franziska Faber Yuhua Zhu Denise N. Bronner Austin J. Byndloss Renée M. Tsolis Huaijun Zhou Andreas J. Bäumler 《Cell host & microbe》2019,25(1):128-139.e5
100.
Khin Thanda Win Juan Vegas Chunying Zhang Kihwan Song Sanghyeob Lee 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2017,130(1):199-211