Abstract This paper reports the application of recently proposed formalism known as generalized population analysis (GPA) a new means for quantitative characterization aromaticity various benzenoid rings in polycyclic aromatic hydrocarbons (PAHs). The quantity which we propose measure is so‐called six‐center bond index. values this index characterize extent delocalized cyclic bonding individual PAHs and it shown that scale represented by closely reflects intuitive idea according to can be...

It is shown that molecular electrostatic potentials obtained from iterative or self-consistent Hirshfeld atomic point charges agree remarkably well with the ab initio computed potentials. The scheme performs nearly as potential derived charges, having advantage of allowing definition atom in molecule, rather than just yielding charges. quality for computing examined a large set molecules and compared to other commonly used techniques population analysis.

Aromatic compounds are characterised by the presence of a ring current when in magnetic field. As consequence, density maps used to assess (the degree of) aromaticity compound. However, often more discrete set so-called Nucleus Independent Chemical Shift (NICS) values is that derived from density. It shown here there no simple one-to-one relationship allows reconstructing only NICS-values. NICS should therefore not be as indices without analysis ab initio computed map.

Abstract The aromaticity and local‐aromaticity of a large set polycyclic aromatic hydrocarbons (PAHs) is studied using multicenter delocalization indices from generalized population analysis the popular nucleus independent chemical shift (NICS) index. A method for fast computation NICS values introduced, so‐called pseudo‐π‐method. detailed examination made multidimensional nature aromaticity. lack good correlation between reported grounds discussed. It shown through thorough statistical that...

The extent of racemization under various circumstances is reported for the coupling N ‐protected model dipeptide Z‐Gly‐Phe to Val‐OMe, mediated by N,N' ‐bis(2‐oxo‐3‐oxazolidinyl)phosphinic chloride (BOC‐Cl). BOP‐Cl can be used peptide syntheses either in a one‐pot reaction or with preactivation. Maximum yields are obtained 1.2 equiv. and 1.2–1.5 amino‐nucleophile 2.2 mediatorial base tetrahydrofuran, but amount stereomutation only tolerable use suppressors (4–6%). BOP‐Cl/ HOBt (88% yield, 0%...

Abstract In a recent contribution, we examined the effect of 10‐ and 14‐center circuits on nucleus‐independent chemical shifts NICSs using multicenter bond indices (MCBIs) (Fias et al., J Comput Chem 2008, 29, 358). this study, nonlocal contributions to NICS are further investigated for larger set polycyclic aromatic hydrocarbons (PAHs). To achieve this, predicted MCBI compared with ab initio results. The central ring perylene‐ benzo‐[ghi]perylene‐like fragments coronene appear have other...

In this study, the dissociation mechanism of self-assembled cyclic peptides (CPs) has been investigated using classical/steered molecular dynamics simulations combined with umbrella sampling techniques in a polar and nonpolar solvent. The stability peptide nanotubes (CPNTs) different surface polarity, {cyclo-[(d-Trp-l-Leu)4]}8 {cyclo-[(l-Gln-d-Ala-l-Glu-d-Ala)2]}8, are explored detail. It is observed from results that CPNTs less dynamic solvent than CPs lower oligomeric form achieved by...

The zz component of the nucleus independent chemical shift or NICSzz is commonly used as a quantifier (anti)aromatic character (sub)system. One underlying assumptions that position can be found where "aromatic" ring currents are adequately reflected in corresponding value. However, result an integration over entire space, it no longer explicitly contains information needed to quantify separate contributions arising from current density patterns. In this study, we will show these revealed by...

Abstract A new computer program has been designed to build and analyze quantitative–structure activity relationship (QSAR) models through regression analysis. The user is provided with a range of validation techniques. emphasis the lies mainly in QSAR chemical applications. ARTE‐QSAR produces an easy interpretable output from which can conclude if obtained model suitable for prediction © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007.

Cyclic peptide nanotubes (CPNTs) formed by the self-assembly of cyclic peptides (CPs) with an even number alternate L/D amino acids are typically used in field transport ions and drug molecules across lipid bilayer. This study investigates mechanism antitumor molecule, 5-fluorouracil (5FU), through CPNT using classical steered molecular dynamics simulations combined umbrella sampling. During 5FU CPNT, is partially desolvated because lumen too small to allow for water solvating it. forms...

Despite correlations with other aromaticity descriptors, the NICS is based on fields that have no features chemists associate aromaticity.

The stability of self-assembling cyclic peptides (CPs) is attained by the intermolecular backbone-backbone hydrogen bonding (H-bonding) interactions. In addition to these H-bonding interactions, self-assembled CPs are further stabilized various side chain-side chain This study investigates role amino acids on structure and using classical molecular dynamics (MD) simulations mechanics/Poisson-Boltzmann surface area (MM/PBSA) method. considered for construction model structures peptide...

Abstract The theoretical basis of quantum Quantitative Structure‐Properties Relationship (QSPR) is analyzed. After setting up a QQSPR operator structure, the first order fundamental equation, which turns to be linear system, deduced. Some algorithms are described afterwards: they based on approximate resolution equation. To show practical computational use theory, definition simple predictive model also developed. Finally an application example given, Cramer steroid set. new procedures can...

Bond Fukui functions and matrices are introduced for ab initio levels of theory using a Mulliken atoms in molecules model. It is shown how these indices may be obtained from first‐order density matrix derivatives without need going to second‐order as previous work. The importance taking into account the nonorthogonality basis calculations shown, contrasting present results with work based on Hückel theory. extension allows getting more insight nature bond functions. All presently respect...

Abstract Structure‐activity relationships of 46 P450 2A6 inhibitors were analyzed using the 3D‐QSAR methodology. The analysis was carried out to confront use traditional steric and electrostatic fields with that a number reflecting conceptual DFT properties: electron density, HOMO, LUMO, Fukui f − function as 3D fields. most predictive models obtained by combining information density ( r 2 = 0.82, q 0.72), yielding statistically significant model. generated model able predict inhibition...

Abstract A simple descriptor, viz the number of carbon ( N C )/non‐hydrogenic NH ) atoms present in a molecule, is proposed for development useful Quantitative Structure–Property–Relationship (QSPR) models. This work prompted by that Randic and Basak J. Chem. Inf. Comput. Sci. 2001 , 41 614–618) who have shown this descriptor superior to connectivity index marginally worse than variable analyzing toxicity aliphatic ethers. It tested models pertaining estimation boiling point alcohols,...

New evidence questioning the multidimensionality of aromaticity phenomenon exemplified in what is called orthogonality between classical (structural and energetic) magnetic indices measures reported. For this purpose, recently proposed methodologies for quantitative characterization energy benefits associated with cyclic arrangement mobile π-electrons polycyclic aromatic hydrocarbons are compared characterizing extent delocalization corresponding conjugated circuits. The reported close...