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排序方式: 共有111条查询结果,搜索用时 15 毫秒
1.
Metabolism of steroid acetates by Streptomyces albus 总被引:1,自引:0,他引:1
Fermentation of 16-dehydropregnenolone acetate (1a) with Streptomyces albus yielded 16-dehydropregnenolone (1b) and 16-dehydroprogesterone (IIa). Similar incubation of pregnenolone acetate (Ic) with the strain afforded pregnenolone (Id), progesterone (IIb) and 20 alpha-hydroxy progesterone (IIc) while dehydroepiandrosterone acetate (IIIa) under the conditions was converted to dehydroepiandrosterone (IIIb), androstenedione (IVa) and testosterone (IVc). The strain was also capable of converting testosterone acetate (IVb) having the 17-acetoxy function in the 5-membered D-ring to testosterone (IVc) and androstenedione (IVa). All the products were identified by the application of various chemical and spectrometric techniques. 相似文献
2.
Two steroidal saponins, floribundasaponins A and B isolated from the yams of Dioscorea floribunda, have been characterized as pennogenin-3-O-β-d-glucopyranoside and pennogenin-3-O-α-l-rhamnopyranosyl(1→4)-β-d-glucopyranoside. 相似文献
3.
The effect of lincocin (a plastid protein synthesis inhibitor) treatment on the greening process of bean (Phaseolus vulgaris L.) leaves have been studied. In comparison with control leaves treated ones had a decreased rate of chloroplast development. They had a marked chlorophyll deficiency and a decreased chlorophyll a/b ratio. Some long and short wavelength forms of chlorophyll a were lacking as evidenced from the absorption spectra at 25°C and the fluorescence spectra at 77°K. The –14CO2 fixation was inhibited by 80–90% in treated leaves. The fluorescence induced by the measuring light was greater in the treated leaves than in the control ones, and the kinetics of the decline of the relative fluorescence intensity were also different. Electron microscopic studies showed macrogranum-like structures and incomplete membrane vesicles in the treated plastids. After longer treatment a destruction of membranes was observed. The results indicate some structural and functional membrane deficiencies and instability of the membranes. 相似文献
4.
Somnath Mahato Arup Ghorai Sanjeev Kumar Srivastava Mantu Modak Sudarshan Singh Samit K. Ray 《Liver Transplantation》2020,10(30)
The synthesis of single‐crystalline β‐CsPbI3 perovskite nanorods (NRs) using a colloidal process is reported, exhibiting their improved photostability under 45–55% humidity. The crystal structure of CsPbI3 NRs films is investigated using Rietveld refined X‐ray diffraction (XRD) patterns to determine crystallographic parameters and the phase transformation from orthorhombic (γ‐CsPbI3) to tetragonal (β‐CsPbI3) on annealing at 150 °C. Atomic resolution transmission electron microscopy images are utilized to determine the probable atomic distribution of Cs, Pb, and I atoms in a single β‐phase CsPbI3 NR, in agreement with the XRD structure and selected area electron diffraction pattern, indicating the growth of single crystalline β‐CsPbI3 NR. The calculation of the electronic band structure of tetragonal β‐CsPbI3 using density functional theory (DFT) reveals a direct transition with a lower band gap and a higher absorption coefficient in the solar spectrum, as compared to its γ‐phase. An air‐stable (45–55% humidity) inverted perovskite solar cell, employing β‐CsPbI3 NRs without any encapsulation, yields an efficiency of 7.3% with 78% enhancement over the γ‐phase, showing its potential for future low cost photovoltaic devices. 相似文献
5.
Taposhi Hazra Manoshi Hazra Sanchita Kumar Sumana Mahato Meghma Bera Subir Bera Mahasin Ali Khan 《植物分类学报:英文版》2021,59(6):1307-1320
Even though presently indigenous to eastern Himalaya in India, no Engelhardioideae have been reported from the Cenozoic sediments of India till date. Here, we report the first Indian occurrence of a characteristic engelhardioid winged samaroid fruit having a tri-lobed wing (oblong-ovate median lobe and two lateral lobes) and a globose nut from the latest Neogene (Pliocene: Rajdanda Formation) sediments of Chotanagpur Plateau, eastern India. This is the first fossil evidence of relict family Juglandaceae from the Indian Cenozoic. We determine its taxonomic position on the basis of detailed macromorphological comparison with similar extant and fossil specimens and discuss its palaeoclimatic significance in terms of the present-day distribution of modern analogous species. We assign this Pliocene winged fruit specimen to the morphogenus Palaeocarya sect. Monocosta Manchester and describe it as a new species, namely Palaeocarya indica Hazra, Hazra M & Khan sp. nov. Palaeocarya sect. Monocosta has rich fossil records from the Cenozoic sediments of Europe, North America, and eastern Asia (China, Korea), but the modern analog, Engelhardia, is presently native only to India and neighboring Southeast Asia. We discuss the possible causes of disappearance of Engelhardia from the present-day vegetation of Chotanagpur Plateau. Its disappearance may be related to the gradual intensification of monsoonal rainfall seasonality since the Pliocene. Here, we also review in detail the biogeographic history of Palaeocarya sect. Monocosta and suggest its possible migration routes. 相似文献
6.
Kaur Parampreet Jindal Suruchi Yadav Bharat Yadav Inderjit Mahato Ajay Sharma Priti Kaur Satinder Gupta O. P. Vrána Jan Šimková Hana Doležel Jaroslav Gill Bikram Singh Meyer Klaus F. X. Khurana J. P. Singh N. K. Chhuneja Parveen Singh Kuldeep 《Molecular biology reports》2020,47(3):1991-2003
Molecular Biology Reports - Diploid A genome wheat species harbor immense genetic variability which has been targeted and proven useful in wheat improvement. Development and deployment of... 相似文献
7.
The recent advances in microbial biotechnology of production of bile acid metabolites helped to identify a number of neutral and acidic steroidal compounds useful as drugs and drug intermediates on a scale which would not have been possible by classical chemical transformations. Microbial transformations viz., hydroxylation, dehydroxylation, reduction of the carbonyl moieties, epimerization, side-chain metabolism, introduction of carbon-carbon double bonds into the steroid nucleus, deconjugation of bile acid conjugates carried out by various microorganisms for production of useful metabolites with special reference to newer techniques including cell immobilization and transposon mutagenesis for selective transformations are reviewed. The different pathways of microbial degradation of bile acids leading to the formation of various products are discussed. A compilation of the metabolites formed by various microorganisms from the bile acids or their conjugates and reported during the period 1979-1992 is also provided. 相似文献
8.
A bacterial strain capable of biotransformation oflantadene A(22-angeloyloxy-3-oxo-olean-12-en-28-oic acid),the pentacyclic hepatotoxin of lantana (Lantanacamara var. aculeata) has been isolated fromsoil using lantadene A as the sole carbon source. Theorganism is Gram negative, rod shaped, motile,catalase positive and has been identified as Alcaligenes faecalis. The isolate has been found tobe specific for lantadene A and did not utilizelantadene B. In studies using sucrose as an additionalcarbon source, A. faecalis elicitedbiotransformation of lantadene A to its trans isomer22-tigloyloxy-3-oxoolean-12-en-28-oic acid,designated as lantadene X and two other minormetabolites which could not be isolated in pure state. 相似文献
9.
A novel water-soluble lipopolymer was synthesized by linking cholesteryl chloroformate to the secondary amino groups of branched poly(ethylenimine) (PEI) of 1,800 and 10,000 Da. Conjugation through PEI secondary amines gives this newly synthesized lipopolymer (abbreviated as PEI-Chol) special advantage over our previously synthesized lipopolymers, which utilized the primary amino groups for conjugation, as the primary amino groups have a significant role in DNA condensation. Also, significantly, only one cholesterol molecule was grafted onto each PEI molecule (confirmed by (1)H NMR and MALDI-TOF mass spectrometry), leaving enough space for the steric interactions of the PEI's primary amines with the DNA. The PEI-Chol lipopolymer was characterized for the critical micellar concentration (cmc), buffer capacity, DNA condensation (by band retardation and circular dichroism), in vitro transfection efficiency, and cell viability. The cmcs of PEI-Chol 1,800 and PEI-Chol 10,000 were 496.6 and 1,330.5 microg/mL, respectively. The acid-base titration indicated high buffering capacity of the polymers around the pH range of 5-7, which indicated their potential for buffering in the acidic pH environment of the endosomes. The band retardation studies indicated that efficient condensation of the plasmid DNA could be achieved using these lipopolymers. The circular dichroism spectra indicated a change in DNA conformation and adoption of lower energy state upon condensation with these lipopolymers when an N/P ratio of 2.5/1 or above was formulated. The mean particle size of these complexes was in the range 110-205 nm, except for the complexes prepared using PEI of 1,800 Da, which had a mean particle size of 384 +/- 300 nm. The zeta potential of DNA complexes prepared using PEI-Chol 1,800, PEI-Chol 10,000 and PEI of 1,800, 10,000, and 25,000 Da at an N/P ratio of 15/1 was in the range 23-30 mV and was dependent on the N/P ratios. The in vitro transfection of PEI-Chol/pCMS-EGFP complexes in Jurkat cells showed high levels of expressed Green Fluorescent Protein (GFP) with little toxicity as determined by flow cytometry. These novel water-soluble lipopolymers provided good transfection efficiency with other desirable characteristics such as water solubility, free primary amino groups for efficient DNA condensation and high buffer capacity that indicated the possibility of efficient endosomal release. 相似文献
10.
David J. Chandler Kristian S. Hansen Bhabananda Mahato Joydeepa Darlong Annamma John Diana N. J. Lockwood 《PLoS neglected tropical diseases》2015,9(1)