Quantum mechanical polar surface area

A correlation has been established between the absorbed fraction of training-set molecules after oral administration in humans and the Quantum Mechanical Polar Surface Area (QMPSA). This correlation holds for the QMPSA calculated with structures where carboxyl groups are deprotonated. The correlation of the absorbed fraction and the QMPSA calculated on the neutral gas phase optimized structures is much less pronounced. This suggests that the absorption process is mainly determined by polar interactions of the drug molecules in water solution. Rules are given to derive the optimal polar/apolar ranges of the electrostatic potential

PG545, a dual heparanase and angiogenesis inhibitor, induces potent anti-tumour and anti-metastatic efficacy in preclinical models

BACKGROUND: PG545 is a heparan sulfate (HS) mimetic that inhibits tumour angiogenesis by sequestering angiogenic growth factors in the extracellular matrix (ECM), thus limiting subsequent binding to receptors. Importantly, PG545 also inhibits heparanase, the only endoglycosidase which cleaves HS chains in the ECM. The aim of the study was to assess PG545 in various solid tumour and metastasis models

Controlled Radical Polymerization of Vinyl Acetate Mediated by a Bis(imino)pyridine Vanadium Complex

Source type: Prin

STRUCTURE AND BONDING STUDIES OF CLX-C2H4 (X=H OR BR) VAN-DER-WAALS COMPLEXES

High-quality ab initio calculations at the MPn (n = 2, 3 or 4) levels for the pi-donor complex formed by HCl and ethene, and the recently characterized ClBr-ethene complex are presented. Interaction energies were calculated with the inclusion of both basis-set superposition error and zero-point energy corrections, resulting in values of about 1 kcal mol(-1) for both complexes. The total charge densities for both complexes yielded molecular graphs indicative of the weak binding in these molecules, and correspondingly, calculated charges showed that the XCl moiety has an overall slightly negative charge, while the ethene moiety is slightly positive. Analysis of the Laplacian of the charge density showed that the geometry of the ClBr-C2H4 complex may be understood in terms of the VSEPR model as an example of an AXYE(3) molecule

The prediction of vibrational frequencies of inorganic molecules using density functional theory

Chemical Physics Letters2823-4219-226CHPL

Ab initio calculations on excited states of VCH

Copyright © 2000 Elsevier Science B.V. All rights reserved.The ground state and various excited states of triplet and singlet VCH have been calculated using ab initio multiple reference configuration interaction (MRCI) methods. The ground state is calculated to be a 3Δ state arising predominantly from the single electron configuration ··8σ2 3π4 9σ1 1δ1 with a calculated V–C bond length of 1.7061 Å and a V–C stretching frequency of 837 cm−1, which are in excellent agreement with experiment. The first excited state is the corresponding isoconfigurational low spin state, 1Δ, which lies 4670 cm−1 above the ground state. Higher excited triplet states are found to correlate well with experimentally known states.Ian Bytheway and Gregory F. Methahttp://www.elsevier.com/wps/find/journaldescription.cws_home/505707/description#descriptio

Stereochemistry of seven-coordinate main group and d(0) transition metal molecules

Ab initio quantum chemical calculations have been used to study the observed preference for the pentagonal bipyramid (PB) geometry in main group heptafluorides (e.g., TeF7-, IF7, and XeF7+) and main group and transition metal oxofluorides MOF(6)(-) (M = I, Re) while the capped octahedron (CO) or capped trigonal prism (CTP) geometry is preferred by the analogous transition metal counterparts (e.g., MoF7- and WF7-). An explanation of these trends is provided by a molecular orbital (MO) model which describes the main group heptafluorides in terms of three non- or antibonding MO's localized largely upon the ligand atoms. These MO's are nonbonding for the PB geometry but slightly antibonding for the CO and CTP geometries because of the lower symmetry of these stereochemistries; thus the PB geometry is predicted for these main group molecules. For transition metal heptafluorides, this MO model predicts that two MO's will not be involved in M-L bond formation as they are localized on the metal atom. Thus for the PB geometry they are nonbonding and slightly antibonding for the CO and CTP geometries. A consequence of the antibonding nature of these orbitals is the slight stabilization of the bonding orbitals and a preference for the CO and CTP geometries. Ab initio calculations of MF(7)(-) (M = Mo, W) molecules predict that the CO and CTP have approximately the same energy and are lower than the PB by approximately 1-4 kcal mol(-1). Similar MO arguments may be applied to ReOF6- for which the PB geometry was calculated to be lower in energy than the CO and CTP geometries by about 28 kcal mol(-1). Total electron densities (rho) of main group and transition metal fluorides and oxofluorides were compared, and strong ionic character was found in both M-F and M-O bonds. Charge concentration maxima in the core regions of the central atoms were found through analysis of the Laplacian of the charge density (del(2) rho) showing that the central atom is distorted by the ligand atoms