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1.
Saikat Haldar Balaji S. Kale Dipesh D. Jadhav Hirekodathakallu V. Thulasiram 《Tetrahedron letters》2014
Pentacyclic triterpenoids α- and β-amyrin possess a wide range of biological and pharmacological activities. High structural similarity between these two structural isomers makes their chromatographic separation an ineffective and tedious choice. In this study, Candida rugosa lipase catalyzed separation protocol for the isolation of individual isomers has been developed. In the presence of vinyl acetate as the acyl donor, Candida rugosa lipase carried out acetylation of β-amyrin more efficiently as compared to α-amyrin leading to a kinetic separation. The conditions of transesterification reaction were optimized systematically, which was utilized to separate α- and β-amyrin from a mixture obtained from the latex of Plumeria obtusa. 相似文献
2.
Farnesyl diphosphate (FPP) synthase catalyzes the consecutive head-to-tail condensations of isopentenyl diphosphate (IPP, C5) with dimethylallyl diphosphate (DMAPP, C5) and geranyl diphosphate (GPP, C10) to give (E,E)-FPP (C15). The enzyme belongs to a genetically distinct family of chain elongation enzymes that install E-double bonds during each addition of a five-carbon isoprene unit. Analysis of the C10 and C15 products from incubations with avian FPP synthase reveals that small amounts of neryl diphosphate (Z-C10) and (Z,E)-FPP are formed along with the E-isomers during the C5 --> C10 and C10 --> C15 reactions. Similar results were obtained for FPP synthase from Escherichia coli, Artemisia tridentata (sage brush), Pyrococcus furiosus, and Methanobacter thermautotrophicus and for GPP and FPP synthesized in vivo by E. coli FPP synthase. When (R)-[2-2H]IPP was a substrate for chain elongation, no deuterium was found in the chain elongation products. In contrast, the deuterium in (S)-[2-2H]IPP was incorporated into all of the products. Thus, the pro-R hydrogen at C2 of IPP is lost when the E- and Z-double bond isomers are formed. The synthesis of Z-double bond isomers by FPP synthase during chain elongation is unexpected for a highly evolved enzyme and probably reflects a compromise between optimizing double bond stereoselectivity and the need to exclude DMAPP from the IPP binding site. 相似文献
3.
Polubarinova-Kochina's analytical differential equation methodis used to determine the pseudo-steady-state solution to problemsinvolving the freezing (solidification) of wedges of liquidwhich are initially at their fusion temperature. In particular,we consider four distinct problems for wedges which are: freezingwith the same constant boundary temperature, freezing with thesame constant boundary heat fluxes, freezing with distinct constantboundary temperatures and freezing with distinct constant fluxesat the boundaries. For the last two problems, a Heun's differentialequation with an unknown singularity is derived, which in bothcases admits a particularly elegant simple solution for thespecial case when the wedge angle is . The moving boundariesobtained are shown pictorially. 相似文献
4.
5.
C. Shobha Devi B. Thulasiram Rajeshwar Rao Aerva Penumaka Nagababu 《Journal of fluorescence》2018,28(5):1195-1205
Copper is a part of various enzymes and helps them to function properly. It can be effectively used to produce promising anticancer drugs and presently, many studies are being pursued worldwide on the development of copper-based complexes as potential anticancer drugs. Herein, we briefly discuss the importance of reactive oxygen species in biological applications and copper(II) complexes as anticancer drugs. The anti-angiogenic properties of mono-nuclear copper(II) complexes have been demonstrated by in vivo chick embryo angiogenesis analysis. The plausible mechanism behind anticancer activity of these complexes is by the formation of excessive intracellular Reactive Oxygen Species (ROS). ROS is a composite term used for oxygen derivative non-radicals and free radicals of highly reactive components, that enhances the killing response of immune cells to microbial invasion. Previous reports have shown that ROS plays an important role as a messenger in cell cycling and normal cell signal transduction. 相似文献
6.
Gas mixing technique has been used in order to increase the current of highly charged ions of Xe at the TIFR-ECRIA. The He, N2, O2, Ne, and Ar are used as support gases, and their effect on output currents of Xe ions is studied. The effective ion charge and the total loss rate of ions are calculated from the measured currents. It is found that molecular gases, such as N2 and O2, exhibit better mixing effect in the enhancement of output of highly charged Xe ions. Furthermore, we describe this 14.5-GHz ECR ion source mounted on a high voltage (400 kV) deck, with its four beamlines, as well as the control system for the remote operation. 相似文献
7.
Mathematical Model of Ice Melting on Transmission Lines 总被引:1,自引:0,他引:1
S. Yu. Sadov P. N. Shivakumar D. Firsov S. H. Lui R. Thulasiram 《Journal of Mathematical Modelling and Algorithms》2007,6(2):273-286
During ice storms, ice forms on high voltage electrical lines. This ice formation often results in downed lines and has been
responsible for considerable damage to life and property as was evidenced in the catastrophic ice storm of Quebec recently.
There are two main aspects, viz., the formation of ice and its timely mitigation. In this paper, we mathematically model the
melting of ice due to a higher current applied to the transmission wire. The two dimensional cross-section contains four layers
consisting of the transmission wire, water due to melting of ice, ice, and the atmosphere. The model includes heat equations
for the various regions with suitable boundary conditions. Heat propagation and ice melting are expressed as a Stefan-like
problem for the moving boundary between the layers of ice and water. The model takes into account gravity which leads to downward
motion of ice and to forced convection of heat in the water layer. In this paper, the results are applied to the case when
the cross-sections are concentric circles to yield melting times for ice dependent on the increase in intensity of the electrical
flow in the line.
This research has been supported in part by Manitoba Hydro and NSERC. 相似文献
8.
C. Shobha Devi B. Thulasiram S. Satyanarayana Penumaka Nagababu 《Journal of fluorescence》2017,27(6):2119-2130
This review describes the analytical techniques used to detect DNA-probes such as Ru(II) complexes with hetero cyclic imidazo phenanthroline (IP) ligands. Studies on drug-DNA interactions are useful biochemical techniques for visualization of DNA both in vitro and in vivo. The interactions of small molecules that binds to DNA are mainly classified into two major classes, one involving covalent binding and another non-covalent binding. Covalent binding in DNA can be irreversible and may leads to inhibition of all DNA processes which subsequently leads to cell death. Usually, covalent interactions leads to permanent changes in the structure of nucleic acids. The non-covalent interaction of molecules with DNA can be due to electrostatic interaction, intercalation and groove binding. These interactions of DNA probes can be explored by various spectroscopic techniques viz. UV–visible, emission, emission quenching spectroscopy, viscosity and thermal denaturation measurements. 相似文献
9.
Swati P. Kolet Dipesh D. Jadhav Balaraman Priyadarshini Bhagyashree N. Swarge Hirekodathakallu V. Thulasiram 《Tetrahedron letters》2014
A fungal system belonging to Mucoraceae family (Mucor piriformis) was explored for the asymmetric reduction of a prochiral ketone, 3-quinuclidinone (I) in an efficient manner to produce an important pharmaceutical precursor (R)-(−)-3-quinuclidinol (II) with ∼96% enantiomeric excess. The efficiency of the process was improved by developing a cation exchange resin (Amberlite IR-120) which assisted the purification of water soluble metabolite II from fermentation media. 相似文献
10.
Ajay Kumar D. Misra A. H. Kelkar U. R. Kadhane K. V. Thulasiram Lokesh C. Tribedi 《Pramana》2007,68(6):983-994
We have studied fast ion-atom and electron-atom collision processes using a reconditioned high resolution X-ray spectrometer.
The X-rays, generated by the collisions, are dispersed by a curved ADP crystal (Johansson geometry) and detected by a gas
proportional counter. A self-written LabVIEW based program has been used to give precise and controlled movement to the crystal
and for data acquisition. The performance was tested by detecting the Kα diagram and satellite lines of several elements.
The Kα satellite lines of Al have been studied in collision with 3–12 keV electrons and 40 MeV C4+ ions. In ion collisions as large as four L-vacancies are created simultaneously with the K-vacancy, compared to two satellites
in case of the e-impact. In addition, we have measured the X-rays from H-, He- and Li-like Si ions which arise due to the
electron loss/capture process in highly charged 80 MeV Si7+ ions in collision with thin carbon foil. Approximate charge state distribution has been obtained using this new technique.
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