Density, Diffusion, and Site-Dipole Field of Solvent around Four Types of Flavonoid Studid by Molecular Dynamics (original) (raw)
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Solute–Solvent Interactions of Flavonoids in Organic Solvents
Journal of Solution Chemistry, 2000
The diffusion coefficients of one flavone and five isoflavones in methanol, ethanol, 2propanol, and acetonitrile were measured at 25 • C by the Taylor-Aris dispersion method. The observed variations of the D values were interpreted in terms of solute-solvent hydrogen-bond interactions and the interpretation was supported by molecular dynamics simulations of two solutes in methanol.
Solute–Solvent Interactions from Diffusion of Flavonoids in Methanol
Journal of Solution Chemistry, 1999
The diffusion coefficients of five commercial flavonoids in methanol were determined at 25°C utilizing the Taylor–Aris dispersion technique. The results provide insight on solute–solvent interactions, in particular, on subtle differences in hydrogen bonding of the various hydroxyl groups of these compounds with the solvent.
The Journal of Physical Chemistry B, 2003
In this paper, we investigate the solvation dynamics of the weakly polar organic solvent tetrahydrofuran (THF) via classical molecular dynamics simulation. We find that the relaxation dynamics of all of the rotational and translational degrees of freedom of neat THF occur on similar time scales and have similar power spectra, making it impossible to use spectral density analysis to discern which specific molecular motions are involved in solvation. Instead, we probe the molecular origins of solvation dynamics using a nonequilibrium projection formalism that we originally outlined in M. J. Bedard-Hearn et al., J. Phys. Chem. A 2003, 107 (24), 4773. Here, we expand this formalism and use it to study the nonequilibrium solvation dynamics for a model reaction in THF in which a charge is removed from an anionic Lennard-Jones (LJ) solute, leaving behind a smaller neutral atom. The solute parameters are chosen to model the photodetachment of an electron from a sodium anion, Naf Na 0 , to compare to the results of ultrafast spectroscopic experiments of this reaction being performed in our lab. We are able to explain the hidden breakdown of linear response for this system that we uncovered in our previous work in terms of the dynamical properties of the neat liquid and the structural properties of the solutions. In particular, our nonequilibrium projection analysis shows that four distinct solvation mechanisms are operative: (1) a rapid relaxation (t e 700 fs) caused by longitudinal translational motions that dramatically change the local solvation structure; (2) a slower relaxation (t > 700 fs) caused by diffusive longitudinal translational motions that completes the transformation of the long-range solute-solvent packing;
Solubility of Flavonoids in Organic Solvents
Journal of Chemical & Engineering Data, 2007
The solubility of quercetin, isoquercitrin, rutin, chrysin, naringenin, and hesperetin was quantified in acetonitrile, acetone, and tert-amyl alcohol. The solubility was strongly affected by both the nature of the solvent and the flavonoid structure. The highest solubility was obtained in acetonitrile for hesperetin (85 mmol‚L-1) and naringenin (77 mmol‚L-1) and in acetone (80 mmol‚L-1) for quercetin. The lowest solubility value was obtained with rutin in acetonirile (0.50 mmol‚L-1). The thermodynamic properties of flavonoids were also measured (melting point, enthalpy of fusion, and solid heat capacity) and predicted (liquid heat capacity, solid phase activity, and activity coefficient). Glycosylated flavonoids are characterized by a low melting point and a high enthalpy of fusion compared to the aglycon ones. Contrary to the data reported for other compounds, there is no clear correlation between the solubility of flavonoids and their thermodynamic properties. However, the conformational study showed that the flavonoids having a torsion angle OC2C1′C6′ of 40°are characterized by a high solubility.
Journal of Computational Chemistry, 1995
The point-chart approximation of the Miertus-Scrocco-Tomasi solvation model (MST-PC) based on a continuum representation of the solvent has been incorporated in force field calculations. Application in molecular mechanics (MM) involves conformational equilibria in solution: rotational isomers of ethylene glycol (I), 1,2-difluoroethane (10, fluoroacetic acid (110, and representative conformers of macrocyclic receptors such as 18-crown-6 (IV), cryptand 2.2.2 (V), and t-butyl-calix[4]arenetetraamide (VI). Assessment of the MST-PC results is based on the comparison with ab initio reactive field calculations (for I-111), with the continuum model of Still (W. C. Still et al., J.
Solvent Structure, Dynamics, and Ion Mobility in Aqueous Solutions at 25 °C
The Journal of Physical Chemistry B, 1998
Brand nd Iat infinite dilution by molecular dynamics simulation using the SPC/E model for water at 25°C and a reaction field for the long-range interactions. The ion mobilities show the same trends as the experimental results with distinct maxima for cations and anions. The mobilities (defined by u i) D i /kT) of the corresponding uncharged species are also determined by simulation and are in qualitative agreement with Stokes' law. The mobilities of Li + , Na + , K + , Rb + and Fincrease on discharge, whereas Cl, Br, and I have smaller mobilities than the corresponding anions. The mobility of the fictitious I + ion, which differs from Ionly in its charge, lies between that of Iand I in the order u I < u I + < u I-. The residence time of water in the first solvation shell of small cations (Li + and Na +) and Ca 2+ decreases when the ions are discharged, while the opposite is observed on neutralizing I-, suggesting the formation of a solvent cage around the large uncharged I which partially breaks up on charging, increasing the mobility of the corresponding ion. The cage breakup is greater for Ithan for I + which correlates with the asymmetry in the entropies of solvation of Iand I + , in SPC/E water on charge reversal, providing an explanation for the trends in the mobilities of I, I-, and I +. The residence times of water in the primary hydration shell around cations pass through a minimum as a function of size that correlates with the maximum in the corresponding solvation entropy, suggesting different types of hydration, i.e., electrostatic ion solvation (hydrophilic) and cage formation (hydrophobic) respectively for small and large cations. The results are in accord with recent calculations of the solvation entropy and free energy as continuous functions of the charge and size (
Journal of Physical Chemistry B, 2001
The expanded ensemble method, developed to calculate solvation free energies, is applied to calculate octanol/ water partition coefficients P for some organic drug-related molecules and compared with experimental results. The experimental log P results were obtained by a miniaturized vial procedure using liquid chromatography with UV for quantification. The expanded ensemble technique, implemented within molecular dynamics scheme, is adapted to treat molecules of arbitrary size and type. For octanol, both all-atom and united atom models are evaluated. The solvation free energy of the organic solute molecules is found to be sensitive to the used sets of partial charges on the atoms in polar groups, particularly in water but also in the saturated octanol phase. Although this effect partially cancels out in the calculated partition coefficients, the charges obtained from ab initio Mulliken population analysis give consistently larger log P values than those obtained in simulations with the larger empirical atomic charges included in the CHARMM force field. In general, calculated log P turned out to be systematically higher than those measured experimentally. The possibility of improving potential models for the solutes in water and oil phase, respectively, is discussed.
Physical Chemistry Chemical Physics, 2006
We investigate the performance of two discrete solvent models in connection with density functional theory (DFT) for the calculation of molecular properties. In our comparison we include the discrete reaction field (DRF) model, a combined quantum mechanics and molecular mechanics (QM/MM) model using a polarizable force field, and the frozen-density embedding (FDE) scheme. We employ these solvent models for ground state properties (dipole and quadrupole moments) and response properties (electronic excitation energies and frequencydependent polarizabilities) of a water molecule in the liquid phase. It is found that both solvent models agree for ground state properties, while there are significant differences in the description of response properties. The origin of these differences is analyzed in detail and it is found that they are mainly caused by a different description of the ground state molecular orbitals of the solute. In addition, for the calculation of the polarizabilities, the inclusion of the response of the solvent to the polarization of the solute becomes important. This effect is included in the DRF model, but is missing in the FDE scheme. A way of including it in FDE calculations of the polarizabilities using finite field calculations is demonstrated.