QSPR predicting the vapor pressure of pesticides into high/low volatility classes.

In this work, the vapor pressure of pesticides is employed as an indicator of their volatility potential. Quantitative Structure-Property Relationship models are established to predict the classification of compounds according to their volatility, into the high and low binary classes separated by the 1-mPa limit. A large dataset of 1005 structurally diverse pesticides with known experimental vapor pressure data at 20 °C is compiled from the publicly available Pesticide Properties DataBase (PPDB) and used for model development.

Conformation-independent quantitative structure-property relationships study on water solubility of pesticides.

Water solubility is a key physicochemical parameter in pesticide control and regulation, although sometimes its experimental determination is not an easy task. In this study, we present Quantitative Structure-Property Relationships (QSPRs) for predicting the water solubility at 20 °C of 1211 approved heterogeneous pesticide compounds, collected from the online Pesticides Properties Data Base (PPDB). Validated and generally applicable Multivariable Linear Regression (MLR) models were established, including molecular descriptors carrying constitutional and topological aspects of the analyzed compounds.

The conformation-independent QSPR approach for predicting the oxidation rate constant of water micropollutants.

In advanced water treatment processes, the degradation efficiency of contaminants depends on the reactivity of the hydroxyl radical toward a target micropollutant. The present study predicts the hydroxyl radical rate constant in water (k ) for 118 emerging micropollutants, by means of quantitative structure-property relationships (QSPR). The conformation-independent QSPR approach is employed, together with a large number of 15,251 molecular descriptors derived with the PaDEL, Epi Suite, and Mold2 freewares.

QSAR on antiproliferative naphthoquinones based on a conformation-independent approach.

The antiproliferative activities of a series of 36 naphthoquinone derivatives were subjected to a Quantitative Structure-Activity Relationships (QSAR) study. For this purpose a panel of four human cancer cell lines was used, namely HBL-100 (breast), HeLa (cervix), SW-1573 (non-small cell lung) and WiDr (colon). A conformation-independent representation of the chemical structure was established in order to avoid leading with the scarce experimental information on X-ray crystal structure of the drug interaction.

Computational modeling of the dizinc-ferroxidase complex of human H ferritin: direct comparison of the density functional theory calculated and experimental structures.

Density functional theory optimizations of structures of dizinc(II) complexes with a six-residue model of the ferroxidase center of human H ferritin have been performed and the results compared with the crystallographically determined structure of the complex as presented in Protein Data Bank file 2CEI. The model employs the full structures of Glu27, Glu62, His65, Glu107, Gln141, and Ala144, and the structural effect of Tyr34 is also examined. The mean absolute deviation from experiment of atomic positions in the best calculated structures is less than 0.

DFT comparison of Fe2+ hydration in the binding sites of the ferroxidase center of bullfrog M ferritin.

Density functional theory optimizations have been conducted on structures of complexes of Fe(2+) with (H(2)O)(n) (n = 0-3) in three-residue models of binding sites A and B of the ferroxidase center of bullfrog M ferritin. Each site is modeled by the full structures of its three active amino acids. The potential surface at each site in the presence of water molecules is complex; coordination numbers of iron from three to six are seen.

Effects of cluster formation on spectra of benzo[a]pyrene and benzo[e]pyrene.

Absorption and fluorescence emission spectra of the polycyclic aromatic hydrocarbons benzo[a]pyrene (BaP) and benzo[e]pyrene (BeP) in solution and adsorbed on silica have been obtained and compared to examine the spectroscopic effects of clustering. Molecular mechanics calculations with the UFF potential were done to optimize monomer, dimer and trimer geometries, and energy differences were determined by MP2/6-31G* calculations. Fluorescence emission spectra of adsorbed BeP and BaP display a red shift that progresses with increased loading, and the two differ in their photodegradation kinetics.

High-spin versus broken symmetry-Effect of DFT spin density representation on the geometries of three diiron (III) model compounds.

Unrestricted density functional theory calculations have been conducted on three diiron(III) synthetic model compounds containing antiferromagnetically coupled high-spin (HS) irons for which crystallographic structures and Raman spectral data are available. Three density functionals have been employed: BPW91, PWC, and BOP. The study compares the effects on optimized geometries and harmonic vibrational frequencies of spin-paired (SP) low-spin, HS, and broken symmetry antiferromagnetically coupled singlet representations of the spin density distribution.

Computational study of iron(II) and -(III) complexes with a simple model human H ferritin ferroxidase center.

Interaction of iron ions with a six-amino acid model of the ferroxidase center of human H chain ferritin has been examined in density functional theory calculations. The model, based on experimental studies of oxidation of Fe2+ at the center, consists of Glu27, Glu62, His65, Glu107, Gln141, and Ala144. Reasonable structures are obtained in a survey of types of iron complexes inferred to occur in the ferroxidase reaction.

Structures and energetics of Be(n)Si(n) and Be(2n)Si(n) (n = 1-4) clusters.

The structures and energies of Be(n)Si(n) and Be(2n)Si(n) (n = 1-4) clusters have been examined in ab initio theoretical electronic structure calculations. Cluster geometries have been established in B3LYP/6-31G(2df) calculations and accurate relative energies determined by the G3XMP2 method. The two atoms readily bond to each other and to other atoms of their own kind.

Hydrogen-bonding conformations of tyrosine B10 tailor the hemeprotein reactivity of ferryl species.

Ferryl compounds [Fe(IV)=O] in living organisms play an essential role in the radical catalytic cycle and degradation processes of hemeproteins. We studied the reactions between H2O2 and hemoglobin II (HbII) (GlnE7, TyrB10, PheCD1, PheE11), recombinant hemoglobin I (HbI) (GlnE7, PheB10, PheCD1, PheE11), and the HbI PheB10Tyr mutant of L. pectinata.