A new method for the estimation of partition coefficient

Receptor binding studies of soft anticholinergic agents

“…All structures were optimized using the AM1 advanced semi-empirical quantum chemical method (39) Twenty-five descriptors were studied in our search for possible relevant parameters: molecular weight (MW); van der Waals molecular volume (V) and surface area ( S) together with the corresponding ovality (O) as a shape descriptor (40); effective van der Waals molecular volume ( V e ) and surface area ( S e ) together with the corresponding ovality (O e ) calculated with a new procedure and a slightly different van der Waals radii set (41); AM1 calculated dipole moment (D), average polarizability (α), ionization energy ( I), and heat of formation; HOMO-LUMO energies (E HOMO , E LUMO ); absolute electronegativity (χ), calculated as the negative of the average HOMO and LUMO energies, and absolute hardness (η), calculated as half the HOMO-LUMO difference; calculated log octanol-water partition coefficient (log P o/w ) using BLOGP (40), QLogP (41,42), and MLOGP (43); calculated log water solubility (log W) using BLOGW (44); AM1-calculated partial atomic charges on the quaternary nitrogen ( q N ) atom and the sp 2 carbon and oxygen atoms of the ester moiety (q C= , q O= ); the distance between the quaternary nitrogen atom and the sp 2 carbon of the ester moiety (d C-N ); and the inaccessible solid angle around these atoms (Ω C , Ω N ) as a measure of steric hindrance (45).…”

“…For all 3 pK i s, O e was a major factor. Ovality, O e , is a parameter that describes the overall size and shape of the molecules (40,41). It is defined as the ratio between the area of the surface of the molecule and that of the minimum surface corresponding to the volume of the molecule (that is, the surface of a sphere with a volume that equals the volume of the molecule).…”

Application of multivariate mathematical-statistical methods to compare reversed-phase thin-layer and liquid chromatographic behaviour of tetrazolium salts in Quantitative Structure-Retention Relationships (QSRR) studies

“…The observations (independent variables) were the tetrazolium salts and the parameters of equation (2), equation (3) with the calculated physico-chemical values for each sample were the variables of following calculation. The physico-chemical parameters included in the calculation were: polarizability (P') [41], refractivity (ρ) [42,43], 10 base logarithm of the lipophilhydrophil character (log π) [43,44], Van der Waals surface (VdW surface ) [45][46][47][48], Van der Waals volume (VdW volume ) [47], water accessible surface (WA surface ) [45][46][47][48], water accessible volume (WA volume ) [47], total energy (E total ), binding energy (E binding ), heat formation (Q f ), energy of the higher occupied molecular orbit (eV HOMO ), energy of the lower unoccupied molecular orbit (eV LUMO ), minimum charge of the atoms (δ min ), maximum charge of the atoms (δ max ) and dipole moment (ξ). These parameters were computed by HyperChem 5.01 with ChemPlus Extension (Hypercube, Waterloo, Canada).…”

Chemical Structure Indices in In Silico Molecular Design

“…In view of its importance, various computational approaches namely, fragmental constants [19,20,24,25], additive atomic contributions [26,27], charge densities [28] and conformationally dependent hydrophobic indices [29,30] are developed to theoretically calculate the logP of a non-ionizable organic compound between two mutually immiscible solvents, 1-octanol and water. Among these computational approaches, fragmental constant methods [19,20,24,25] are the most popular ones.…”