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141.
The microbial metabolism of primaquine, a 6-methoxy-8-aminoquinoline antimalarial agent, was investigated. The yeast Candida tropicalis was found to convert primaquine to the previously reported N-acetylated derivative. On continued incubation of C. tropicalis in the presence of the N-acetylated derivative, a minor dimeric metabolite was formed. The proposed structure of the metabolite was based primarily on the analysis of its spectroscopic properties (1H and 13C nuclear magnetic resonance spectra and field-desorption mass spectrum). The structure of the metabolite was proven by direct comparison with an authentic sample of the minor dimeric metabolite prepared by treatment of the N-acetylated derivative with formaldehyde in the presence of formic acid in methanol. 相似文献
142.
R. K. Gupta 《Plant Ecology》1978,37(2):111-118
Summary Effects of human influences on the vegetation of the Western Himalaya have been reviewed. Impacts of forest management practices, over-grazing, surface mining, defence and development operations, and road building activities, are severe in the region. This has created an alarming situation for soil and water conservation. Increased soil loss and runoff pose a threat to various reservoirs built for various uses and have increased hazards of erosion and floods in the Indus and Ganga basin regions.Nomenclature follows Hooker (1872–1897) and Gupta (1968). 相似文献
143.
Tween-80 supplementation in submerged culture ofAspergillus fumigatus resulted in an increase of phosphate uptake. The uptake system was characterized as saturable, energy-dependent and operating
against the concentration gradient. Control and Tween 80 cultures showed similarK
m
values for phosphate uptake (50 μm). Cold osmotic shock treatment of the cultures was found to cause considerable reduction
in the ability to take up phosphorus with concomitant release of the binding protein into the shock fluid. Binding protein
preparation from Tween-80 supplemented cells showed more activity than that from control cells. 相似文献
144.
R K Gupta 《The Journal of biological chemistry》1977,252(15):5183-5185
This communication introduces a nuclear relaxation approach for an estimation of the distance between two paramagnetic metal ion sites on a metal-activated enzyme. The method is based on the existence of an exchange of unpaired electron spin magnetizations between the two metals via energy-conserving concerted mutual spin flips which arise from time-dependent dipolar interactions of the electronic magnetizations. This cross-relaxation of electronic magnetizations depends on the inverse sixth power of the intermetal distance and may, under suitable conditions, affect the longitudinal relaxation rate of inner sphere water protons by altering the electron-proton dipolar correlation time when the latter is dominated by electron spin relaxation. The technique is applied to estimate the distance of 5.2 +/- 0.9 A between Mn2+ and Cr3+ in the pyruvate kinase-Mn2+-ATPCr3+ complex and indicates the existence of a van der Waals contact between the hydration spheres of the enzyme- and nucleotide-bound metal ions. 相似文献
145.
Biosynthesis of aflatoxins. 总被引:23,自引:0,他引:23
146.
Stable mutants resistant to the protein synthesis inhibitors cryptopleurine and tylocrebine can be isolated in Chinese hamster ovary (CHO) cells, in a single step. The frequency of occurrence of cryptopleurine (CryR) and tylocrebrine (TylR) resistant mutants in normal and mutagenized cell populations is similar to that observed for emetine resistant (EmtR) mutants. The CryR, TylR, and EmtR mutants exhibit strikingly similar cross-resistance to the three drugs used for selection, to tubulosine and also to two emetine derivatives cephaeline and dehydroemetine, based on assays of in vivo cytotoxicity and on assays of protein synthesis in cell-free extracts. The identity of cross-resistance patterns of the CryR, TylR, and EmtR mutants indicates that the resistance to all these compounds results from the same primary lesion, which in the case of EmtR cells has been shown to affect the 40S ribosomal subunit. This conclusion is strongly supported by the failure of EmtR, TylR, and CryR mutants to complement each other in somatic cell hybrids. Based on these results it is suggested that the above group of compounds possesses common structural determinants which are responsible for their activity. The above mutants, however, do not show any cross-resistance to other inhibitors of protein synthesis such as cycloheximide, trichodermin, anisomycin, pactamycin, and sparsomycin, either in vivo or in vitro, indicating that the site of action of these inhibitors is different from that of the emetine-like compounds. 相似文献
147.
Mycelium of Fusarium oxysporum grown on a glucose-containing medium lacked fructosyl transferase and invertase activities. Synthesis of fructosyl t 相似文献
148.
Two new compounds G and H isolated from the roots of Costus speciosus have been characterized as 8-hydroxytriacontan-25-one and Me tritriacontanoat 相似文献
149.
Ferdinand Bohlmann Rajinder K. Gupta Robert M.^King Harold Robinson 《Phytochemistry》1982,21(10):2593-2595
Calea villosa afforded three new sesquiterpene lactones, two furanoheliangolides and an epoxy- germacranolide, as well as several known compounds. The structures were elucidated by spectroscopic methods. 相似文献
150.
Eight healthy male animals were inducted and kept for 2 1/2 years at 3 650 m altitude and subjected to normal work schedules. Physiological measurements viz. heart rate, blood pressure, minute ventilation, oxygen consumption, respiration rate, hemoglobin, packed cell haematocrit volume and eosinophil count were made on these animals at periodic intervals. On acute induction to an altitude of 3 650 m these animals demonstrated a sudden increase in tidal volume, a decrease in Rf and no change in VE, suggesting a decreased dead space/tidal volume ratio at altitude.However, all these changes stabilised within 3 weeks but on prolongation of stay, the physical state of these animals was adversely affected. The respiratory adjustments occurring on return to sea level appear to be a response to thermal stress. The initial increase in heart rate and blood pressure stabilised by the 2nd week. 相似文献