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81.
82.
Tathagata Basak 《Journal of Pure and Applied Algebra》2018,222(10):3036-3042
83.
The present study was designed to determine the composition of the essential oil of Eucalyptus camaldulensis Dehnh. leaves and to examine its in vitro antioxidant and antidiabetic activities. The chemical composition of the essential oil from Eucalyptus camaldulensis Dehnh. leaves was analyzed by GC/GC-MS, twenty-nine compounds representing 99.10% of the total oil were identified. The major components of the oil were p-cymene (68.43%), 1,8-cineole (13.92%), 1-(S)-α-pinene (3.45%) and R-(+)- limonene (2.84%). The antioxidant features of the essential oil were evaluated using inhibition of 2,2-diphenyl-1-picrylhydrazyl, hydroxyl, and superoxide radicals, inhibition of hydrogen peroxide and lipid peroxidation assays. We also studied α-amylase and α-glucosidase inhibition in vitro to assess the antidiabetic properties of the essential oil. Both α-amylase and α-glucosidase were inhibited by a non-competitive mechanism. 相似文献
84.
The equation of transfer for interlocked multiplets in anisotropically scattering atmosphere with planetary phase function has been considered. The Planck function is considered as exponential function of optical depth. The diffusely reflected intensity and emergent intensity in nth approximation has been obtained. Attempt has been made to get exact diffusely reflected intensity and emergent intensity. 相似文献
85.
The Pummerer reaction of an o-benzoyl-substituted pyridylmethyl sulfoxide generates an alpha-thiocarbocation, the interception of which by a neighboring keto functionality produces an alpha-thio-substituted furo[3,4-c]pyridine as transient intermediate; the latter undergoes a Diels-Alder cycloaddition with an added dienophile. Base-induced ring opening of the cycloadduct followed by aromatization gives an isoquinoline derivative that may be looked upon as a heterocyclic analogue of 1-arylnaphthalene lignans. This procedure occurs readily with electron-poor dienophiles and the entire sequence can be run in one pot. The facility of the sequential Pummerer-Diels-Alder reaction hinges on the experimental conditions, the best results being obtained with heptafluorobutyric anhydride as the triggering agent in toluene containing a catalytic amount of p-toluenesulfonic acid. In the absence of a dienophile it is possible to isolate and characterize a rather unstable furo[3,4-c]pyridine derivative. An intramolecular variant of this protocol is also feasible with use of unactivated alkenyl tethers of variable length; however, the bridged cycloadducts are unisolable in these cases as they undergo spontaneous ring opening and aromatization to yield cycloalka[h]isoquinolines. The usefulness of the sequential Pummerer-Diels-Alder reaction is further demonstrated through the synthesis of a heterolignan with a built-in lactone ring via oxidation of the initial [4+2]-cycloadduct followed by extrusion of phenyl sulfinate and elaboration of the resulting hydoxylated isoquinoline derivative. 相似文献
86.
Subir K. Basak Ajoy Velayudhan Michael R. Ladisch 《Applied biochemistry and biotechnology》1994,44(3):243-261
Buffers used in electrophoresis and electrochromatography must have a relatively low ionic strength in order to minimize ohmic
heating in the presence of an applied potential. Calculation of pH, ionic strength, and the van Slyke buffer capacity, β,
is therefore important. This paper describes thea priori calculation of these parameters for tris buffer made up with either glycine (a zwitterion) or HCl. A quadratic expression
for pH, valid over wide ranges, is obtained for both buffer systems. The calculated values of pH, ionic strength, and buffer
capacity are shown to agree with experimental results as a function of tris, HCl, and glycine concentrations ranging from
1 to 50 mM. A new parameter, the electrokinetic buffer effectiveness factor, is introduced to characterize buffers being considered
for use in electrokinetic systems such as electrochromatography, and is used to determine the appropriate composition ranges
for the buffer components. 相似文献
87.
B. Basak U. K. Bhattacharyya A. Sinhababu S. Laskar 《Applied biochemistry and biotechnology》1994,49(3):281-290
Studies have been carried out on the protein solubility profile of Kulthi (Macrotylona uniflorus, Lam.) seed in aqueous solution over various pHs and at different concentrations of NaCl, Na2SO3, CaCl2, and MgCl2 at pH 8.0. Amino acid analysis of isolated protein identified 17 amino acids, 9 of which are essential. Gel-permeation chromatography on Sephadex G-200 revealed the presence of seven components in the protein fraction. Their molecular weights were determined by two comparable standard methods. Extractable Kulthi seed proteins in salt solutions were separated electrophoretically into eight fractions whose molecular weights were found to be 186,200, 131,800, 108,400, 91,200, 53,700, 44,700, 38,000, and 27,500. 相似文献
88.
J.S. Yadav B.V. Subba Reddy Ashutosh Pratap Singh A.K. Basak 《Tetrahedron letters》2007,48(42):7546-7548
Baylis-Hillman adducts undergo smooth one-pot oxidative Michael addition with allyltrimethylsilane in the presence of 2-iodoxybenzoic acid (IBX)/Sc(OTf)3 under mild conditions to afford homoallyl β-ketoesters in good yields with high 1,4-selectivity. 相似文献
89.
Activated aryl halides undergo smooth nucleophilic substitution reactions with secondary amines in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) or 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) ionic liquids (ILs) at room temperature to afford the corresponding arylamines in excellent yields under mild and neutral conditions. 相似文献
90.
Assessing model fit by cross-validation 总被引:8,自引:0,他引:8
Hawkins DM Basak SC Mills D 《Journal of chemical information and computer sciences》2003,43(2):579-586
When QSAR models are fitted, it is important to validate any fitted model-to check that it is plausible that its predictions will carry over to fresh data not used in the model fitting exercise. There are two standard ways of doing this-using a separate hold-out test sample and the computationally much more burdensome leave-one-out cross-validation in which the entire pool of available compounds is used both to fit the model and to assess its validity. We show by theoretical argument and empiric study of a large QSAR data set that when the available sample size is small-in the dozens or scores rather than the hundreds, holding a portion of it back for testing is wasteful, and that it is much better to use cross-validation, but ensure that this is done properly. 相似文献