Binding energies to pyrrole were determined for a number of main-group and transition-metal cations (both monomer complexes with one pyrrole ligand and dimer complexes with two ligands). Experimental data were obtained by radiative association kinetics measurements in the Fourier transform ion cyclotron resonance ion trapping mass spectrometer, along with ligand exchange equilibrium determinations (for the Mg + and Al + cases) using benzene as the reference ligand. Density functional calculations using the B3LYP hybrid functional were carried out on all complexes. The calculations indicated binding only to the π site of pyrrole, with no significantly stable binding site being found for binding of any metal ion in the vicinity of the nitrogen. Experimental binding energies for the transition-metal monomer complexes were parallel to previously reported benzene values. Mg + and Al + were more strongly bound to pyrrole than benzene, presumably due to the dipole moment of pyrrole. The quantum chemical binding energy values for the monomers were reasonably parallel to the experimental values, but were generally lower by a few kcal/mol. For the dimer complexes, the experimental and quantum chemical values were in satisfactory agreement. The pyrrole transition-metal dimers contrasted strongly with the trend previously reported for the corresponding benzene dimers, showing relatively weaker binding for the early transition metals falling to a minimum at Mn + , rising sharply for the later transition metals, and dipping again for Cu + .
Binding energies are estimated for the complexes of benzene with the first-row transition-metal ions (M+ =
Ti+−Cu+) via both kinetic modeling and quantum chemical simulation. A variational transition-state theory
model implementing an ion−quadrupole plus ion-induced dipole potential is employed in the modeling of
the kinetic data for the collision-induced dissociation of these complexes. For Cr+, a global potential is generated
for its interaction with benzene and radiative association experiments are also modeled. Implementation of
this potential in the transition-state analyses indicates only minor anharmonicity effects for the complex state
density near the dissociation threshold and negligible deviation from the long-range potential-based predictions
for the transition-state partition functions. Theoretical optimized geometries, binding energies, and vibrational
frequencies are determined with the B3LYP (Becke-3 Lee−Yang−Parr) density functional. The V+, Ni+,
and Fe+ complexes are found to have modest Jahn−Teller-induced boat-shaped distortions of the benzene
ligand. The quantum chemical and kinetic modeling based estimates for the binding energies are in reasonable
agreement.
Direct current resistivity data acquired on rough terrain can be interpreted by using an appropriate inversion technique after a topographic correction. In order to avoid the influence of a possibly incomplete topographic correction, an improved two-dimensional resistivity inversion algorithm has been developed to estimate the subsurface resistivity distribution in the presence of topography.In this paper, fully discretized modeling is based on the finite-element method, and the iterative inversion scheme is derived from the second-order Marquardt damped least-squares method. The algorithm has been tested on both synthetic and field resistivity data with topography incorporated explicitly into the inversion model. Both theoretical and field studies indicate that the technique is computationally efficient and provides an improved geologic interpretation for complex subsurface structures. A four-electrode configuration is used in the algorithm so that the inversion can represent most field measurements.
Based on our finding that the antitumor effect of 5-(4-((1-methylcyclohexyl)methoxy)benzyl)thiazolidine-2,4-dione, a thiazolidinedione peroxisome proliferator-activated receptor (PPAR)γ agonist, was, in part, attributable to its ability to block glucose uptake independently of PPARγ, we used its PPARγ-inactive analogue to develop a novel class of glucose transporter (GLUT) inhibitors. This lead optimization led to compound 30 (5-(4-hydroxy-3-trifluoromethyl-benzylidene)-3-[4,4,4-trifluoro-2-methyl-2-(2,2,2-trifluoro-ethyl)-butyl]-thiazolidine-2,4-dione) as the optimal agent, which exhibited high antitumor potency through the suppression of glucose uptake (IC50, 2.5 μM), while not cytotoxic to prostate and mammary epithelial cells. This glucose uptake inhibition was associated with the inhibition of GLUT1 (IC50, 2 μM). Moreover, the mechanism of antitumor action of compound 30 was validated by its effect on a series of energy restriction-associated cellular responses. Homology modeling analysis suggests that the inhibitory effect of compound 30 on glucose entry was attributable to its ability to bind to the GLUT1 channel at a site distinct from that of glucose.
The first photoabsorption band of water around 8 eV is studied with the molecular dynamics computer simulation technique under ambient and supercritical conditions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.