Regioselective Mono-<Emphasis Type="Italic">O</Emphasis>-Carboxymethylation of Polyhydroxyisoflavones

Optimized conditions are described for the regioselective mono-O-alkylation of daidzein 1a, genistein 1b, and biochanin A 1c with ethyl bromoacetate.     

Thermodynamic analysis of MHD Couette–Poiseuille flow of water-based nanofluids in a rotating channel with radiation and Hall effects

Journal of Thermal Analysis and Calorimetry - This study will focus on the first- and second-law analyses of MHD Couette–Poiseuille flow of water-based nanofluids in a rotating permeable...     

Methane hydrate formation and decomposition: structural studies via neutron diffraction and empirical potential structure refinement

Neutron diffraction studies with hydrogen/deuterium isotope substitution measurements are performed to investigate the water structure at the early, medium, and late periods of methane clathrate hydrate formation and decomposition. These measurements are coupled with simultaneous gas consumption measurements to track the formation of methane hydrate from a gas/water mixture, and then the complete decomposition of hydrate. Empirical potential structure refinement computer simulations are used to analyze the neutron diffraction data and extract from the data the water structure in the bulk methane hydrate solution. The results highlight the significant changes in the water structure of the remaining liquid at various stages of hydrate formation and decomposition, and give further insight into the way in which hydrates form. The results also have important implications on the memory effect, suggesting that the water structure in the presence of hydrate crystallites is significantly different at equivalent stages of forming compared to decomposing. These results are in sharp contrast to the previously reported cases when all remaining hydrate crystallites are absent from the solution. For these systems there is no detectable change in the water structure or the methane hydration shell before hydrate formation and after decomposition. Based on the new results presented in this paper, it is clear that the local water structure is affected by the presence of hydrate crystallites, which may in turn be responsible for the "history" or "memory" effect where the production of hydrate from a solution of formed and then subsequently melted hydrate is reportedly much quicker than producing hydrate from a fresh water/gas mixture.     

Quantification of isoflavones and lignans in serum using isotope dilution liquid chromatography/tandem mass spectrometry

Phytoestrogens (isoflavones and lignans) are receiving increasing attention due to a potential protective effect against a number of complex diseases. However, in order to investigate these associations, it is necessary to accurately quantify the levels of phytoestrogens in foods and biological fluids. We report an assay for three isoflavones (daidzein, genistein, and glycitein), two metabolites of daidzein (O-desmethylangolensin and equol), and two lignans (enterodiol and enterolactone) in human serum using electrospray ionisation liquid chromatography/mass spectrometry (LC/MS) with selective reaction monitoring. A simple, highly automated sample preparation procedure requires only 200 microL of sample and utilises one solid-phase extraction stage. Limits of detection are in the region of 10 pg/mL for all analytes except equol, which had a limit of detection of approximately 100 pg/mL. The method developed is suitable for measuring the concentrations of phytoestrogens in blood samples collected from large epidemiological studies. The results of the analysis of serum samples from 300 men and women living in the UK are reported.     

Synthesis of lupiwighteone via a para-Claisen-Cope rearrangement

The lanthanide catalysed para-Claisen-Cope rearrangement has been used as the key step in a short synthesis of the prenylated isoflavone, lupiwighteone. The Mitsunobu reaction was employed for the 5-O-prenylation of the acid/base sensitive acetylated isoflavone to afford the allyl aryl ether precursor, which was then rearranged under mild conditions in good yield. Rearrangement of the isoflavone gave the 8-prenylisoflavone as a single product, in good yield.     

Design,synthesis and molecular docking of new [1,2,4] triazolo[4,3-a]quinoxaline derivatives as anticancer agents targeting VEGFR-2 kinase

Molecular Diversity - Vascular endothelial growth factor receptor-2 (VEGFR-2) is critically involved in cancer angiogenesis. Blocking of VEGFR-2 signaling pathway proved effective suppression of...     

A comparison of generalized hybrid Monte Carlo methods with and without momentum flip

The generalized hybrid Monte Carlo (GHMC) method combines Metropolis corrected constant energy simulations with a partial random refreshment step in the particle momenta. The standard detailed balance condition requires that momenta are negated upon rejection of a molecular dynamics proposal step. The implication is a trajectory reversal upon rejection, which is undesirable when interpreting GHMC as thermostated molecular dynamics. We show that a modified detailed balance condition can be used to implement GHMC without momentum flips. The same modification can be applied to the generalized shadow hybrid Monte Carlo (GSHMC) method. Numerical results indicate that GHMC/GSHMC implementations with momentum flip display a favorable behavior in terms of sampling efficiency, i.e., the traditional GHMC/GSHMC implementations with momentum flip got the advantage of a higher acceptance rate and faster decorrelation of Monte Carlo samples. The difference is more pronounced for GHMC. We also numerically investigate the behavior of the GHMC method as a Langevin-type thermostat. We find that the GHMC method without momentum flip interferes less with the underlying stochastic molecular dynamics in terms of autocorrelation functions and it to be preferred over the GHMC method with momentum flip. The same finding applies to GSHMC.     

The Solubility and Solvation of Salts in Mixed Nonaqueous Solvents. 2. Potassium Halides in Mixed Protic Solvents

The solubilities of potassium fluoride, chloride, and bromide in ethanol, formamide, and N-methylformamide and in binary mixtures of these solvents were determined at 25°C. The standard molar Gibbs energies of solution, Δ_soln G ^o, in the neat solvents were related to their hydrogen bonding abilities. The values of Δ_soln G ^o in the mixtures were fitted with expressions of the quasilattice quasichemical theory, and the preferential solvation of the ions was thereby established.