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851.
The main functions of glycosylation are stabilization, detoxification and solubilization of substrates and products. To produce glycosylated products, Escherichia coli was engineered by overexpression of TDP‐L ‐rhamnose and TDP‐6‐deoxy‐D ‐allose biosynthetic gene clusters, and flavonoids were glycosylated by the overexpression of the glycosyltransferase gene from Arabidopsis thaliana. For the glycosylation, these flavonoids (quercetin and kaempferol) were exogenously fed to the host in a biotransformation system. The products were isolated, analyzed and confirmed by HPLC, LC/MS, and ESI‐MS/MS analyses. Several conditions (arabinose, IPTG concentration, OD600, substrate concentration, incubation time) were optimized to increase the production level. We successfully isolated approximately 24 mg/L 3‐O‐rhamnosyl quercetin and 12.9 mg/L 3‐O‐rhamnosyl kaempferol upon feeding of 0.2 mM of the respective flavonoids and were also able to isolate 3‐O‐allosyl quercetin. Thus, this study reveals a method that might be useful for the biosynthesis of rhamnosyl and allosyl flavonoids and for the glycosylation of related compounds. Biotechnol. Bioeng. 2010;107: 154–162. © 2010 Wiley Periodicals, Inc. 相似文献
852.
Lead (Pb) toxicity has been a serious concern in industrialized societies because of its association with functional deficits in nervous, haematopoietic and renal systems. Several studies have shown beneficial effects of thiamine on Pb toxicity. It is speculated that Pb chelation by thiamine may be a possible mechanism. However, the exact nature of these interactions remained elusive. In the present study we have characterized the interaction of Pb with thiamine using UV–Vis as well as fluorescence spectroscopic methods and studied the effect of thiamine treatment on blood and tissue Pb levels during simultaneous or post-exposure to Pb in rat model. The spectroscopic studies revealed that Pb interacts with the pyrimidine ring of thiamine, leading to its solubilization at physiological pH. Further, thiamine reduced the Pb levels in blood, kidney and bone during both simultaneous and post-exposure Pb treatment. Interestingly, thiamine appears to prevent the accumulation of Pb in bone during simultaneous treatment. Together these results suggest that pyrimidine ring of thiamine mediates its interaction with Pb, leading to the prevention of its accumulation and/or increased clearance from tissues. 相似文献
853.
854.
On micropolar fluid model for blood flow through narrow tubes 总被引:1,自引:0,他引:1
855.
Shibnath Ghosal Potharaju H. Rao Dinesh K. Jaiswal Yatendra Kumar August W. Frahm 《Phytochemistry》1981,20(8):2003-2007
From the bulbs of Crinum pratense, collected at flowering, lycorine, 1,2-diacetyllycorine, ambelline, narcissidine, and three phenanthridone alkaloids, viz. hippadine, pratorinine and anhydrolycorin-7-one, were isolated and characterized on the basis of comprehensive spectral analyses (UV, IR, 1H NMR, 13C NMR, MS, [α]D) and chemical evidence. Among the phenanthridone alkaloids (1–3, only the natural occurrence of hippadine was previously known. Pratorinine is a new phenanthridone alkaloid and anhydrolycorin-7-one was known before only as a synthetic compound. The physiological significance of hippadine is appraised. 相似文献
856.
Bella Devassy Tony Dinesh Goyal Sunil Khanna 《Journal of industrial microbiology & biotechnology》2009,36(7):955-960
Aerobic mixed bacterial culture comprised of five isolates (Bacillus vallismortis, B. pumilus, B. cereus, B. subtilis and B. megaterium) identified by 16srDNA analysis was developed from wastewater samples from the aeration tank of an effluent treatment plant
of a textile and dyeing industry and evaluated for its ability to decolorize azo dye Direct Red 28 in an up-flow immobilized
packed bed bioreactor using marble chips as support matrix. The bioreactor was operated under two parameters: an aeration
rate of 0.4 and 0.6 mmol/min at a flow rate of 60, 90 and 120 ml/h, respectively. At a constant aeration rate of 0.4 mmol/min
and with flow rates of 60, 90 and 120 ml/h, optimum decolorization of 91, 75 and 72% was observed, while at an aeration rate
of 0.6 mmol/min and flow rates of 60, 90 and 120 ml/h, optimum decolorization of 93, 78 and 72% was observed over 10 days.
The study concluded that across the two aeration rates and the respective flow rates, the higher aeration rate of 0.6 mmol/min
along with a flow rate of 60 ml/h was best suited to decolorize Direct Red 28 in the packed bed bioreactor. Spectral changes
of the input and output of the bioreactor by UV–visible spectroscopy indicated decolorization of the dye solution by degradation
in addition to the visual observation of the biosorption process. 相似文献
857.
858.
Dinesh S. Bhoj Mohammad Ahsanullah 《Biometrical journal. Biometrische Zeitschrift》1994,36(2):153-163
Consider the two linear regression models of Yij on Xij, namely Yij = βio + βij, Xij + Eij = 1, 2,…, ni, i = 1, 2, where Eij are assumed to be normally distributed with zero mean and common unknown variance σ2. The problem of estimating the conditional mean of Y1 for a given value of X1 is considered when it is a priori suspected that β10 = β20 and β11 = β21. The preliminary test estimator is proposed. The exact expressions for the bias and the mean square error of the estimator are derived. The relative efficiency of the new estimator to the usual least square estimator based on the first regression alone is computed and is used to determine the appropriate value of the significance level of the preliminary test β10 = β20 and β11 = β21. 相似文献
859.
Irina Orlova Dinesh A. Nagegowda Christine M. Kish Michael Gutensohn Hiroshi Maeda Marina Varbanova Eyal Fridman Shinjiro Yamaguchi Atsushi Hanada Yuji Kamiya Alexander Krichevsky Vitaly Citovsky Eran Pichersky Natalia Dudareva 《The Plant cell》2009,21(12):4002-4017
Geranyl diphosphate (GPP), the precursor of many monoterpene end products, is synthesized in plastids by a condensation of dimethylallyl diphosphate and isopentenyl diphosphate (IPP) in a reaction catalyzed by homodimeric or heterodimeric GPP synthase (GPPS). In the heterodimeric enzymes, a noncatalytic small subunit (GPPS.SSU) determines the product specificity of the catalytic large subunit, which may be either an active geranylgeranyl diphosphate synthase (GGPPS) or an inactive GGPPS-like protein. Here, we show that expression of snapdragon (Antirrhinum majus) GPPS.SSU in tobacco (Nicotiana tabacum) plants increased the total GPPS activity and monoterpene emission from leaves and flowers, indicating that the introduced catalytically inactive GPPS.SSU found endogenous large subunit partner(s) and formed an active snapdragon/tobacco GPPS in planta. Bimolecular fluorescence complementation and in vitro enzyme analysis of individual and hybrid proteins revealed that two of four GGPPS-like candidates from tobacco EST databases encode bona fide GGPPS that can interact with snapdragon GPPS.SSU and form a functional GPPS enzyme in plastids. The formation of chimeric GPPS in transgenic plants also resulted in leaf chlorosis, increased light sensitivity, and dwarfism due to decreased levels of chlorophylls, carotenoids, and gibberellins. In addition, these transgenic plants had reduced levels of sesquiterpene emission, suggesting that the export of isoprenoid intermediates from the plastids into the cytosol was decreased. These results provide genetic evidence that GPPS.SSU modifies the chain length specificity of phylogenetically distant GGPPS and can modulate IPP flux distribution between GPP and GGPP synthesis in planta. 相似文献
860.