seven stilbenes and one catechin were bioactivity-guidedly isolated from the rhizomes of rheum palmatem. their structures were identified as piceatannol(1), resveratrol(2), piceid(3), rhapontigenin(4), piceatannol-3'-o-β-d-glucopyranoside(5), rhaponticin(6), catechin(7) and desoxyrhapontigenin(8). anti-monoamine oxidase (mao) activities of compounds 1–8 were tested. compounds 1 and 8 showe...

background and objectives: the usepa has suggested faecal enterococci as the primary bacterial indicators. of more importance is their direct correlation with swimmer-associated gastroenteritis in recreation water quality monitoring. in contrast to other seawater bodies with 3.5% salinity, the recreational waters in the southern coast of the caspian sea possess its own salinity (about 1% w/v) a...

an important property that has been extensively studied in quantitative structure activityrelationship (qsar) is the chromatographic retention index. qsar study is suggested for theprediction of retention index of alkanes and alkenes compounds. modeling of the retention indexof alkanes and alkenes compounds as a function of molecular structures was established bydifferent chemometrics methods. ...

nbo analysis and density functional theory (dft: b3lyp/6-311+g**) based method were used to study the impacts of the anomeric effects (ae) on the conformational properties of 2-methoxy-1,2,4,5-tetrahydro-benzo[d]oxepine (1), -thiepine (2) and -selenepine (3). the gibbs free energy difference (geq–gax) values (i.e. δgeq-ax) at 298.15 k and 1 atm between the axial and equatorial conformations inc...

the insertion of an olefinic c=c bond into a metal-carbon bond is of potential interest as a preparativeroute to new products and as results of c-c coupling reactions to organic compounds. the allyl compoundsof mg, react with an olefin by inversion of the allyl group via a six center transition state. these precyclicreactions may be one of the most important classes of organic reactions. the re...

An important property that has been extensively studied in quantitative structure activityrelationship (QSAR) is the chromatographic retention index. QSAR study is suggested for theprediction of retention index of alkanes and alkenes compounds. Modeling of the retention indexof alkanes and alkenes compounds as a function of molecular structures was established bydifferent chemometrics methods. ...

glycine, alanine and valine are taken as amino acids with an equal polar head and with thedifference in the length of hydrocarbon chains. the structural optimizations show the results of theisolated glycine, alanine and valine in the gases phase, at the hartree-fock level by means ofsto-3g,3-21g, 6-31g and 6-31+g basis sets. the calculations were performed for the ten (1-10)solvents using pcm m...

molecular understanding of three-dimensional (3d) peptide: mhc models require both basic knowledge of computational modeling and skilled visual perception, which are not possessed by all students. the present model aims to simulate mhc molecular structure with the hands and make a profound impression on the students.

in current work a comprehensive mechanism based on intermediate radical termination theory is assumed for raft polymerization of styrene over cumyl dithiobenzoate as raft agent. rate constants for addition (ka) and fragmentation reactions (kf) are set to 6×106 and 5×104 respectively, which lead to an equilibrium constant value of k = ka/kf = 1.2 x 102. moment equations method was used to model ...

an interactive application, modelface, was presented for modeller software based on windows platform. the application is able to run all steps of homology modeling including pdb to fasta generation, running clustal, model building and loop refinement. other modules of modeler including energy calculation, energy minimization and the ability to make single point mutations in the pdb structures a...