Residues of chlorinated pesticides in mother\u27s milk and child\u27s serum

Uzorci mlijeka i seruma 27 hospitaliziranih dojilja iz Bjelovara i Zaboka s okolnim mjestima analizirani su na ostatke kloriranih insekticida aldrina, dieldrina, endrina, heptaklora, heptaklor epoksida, lindana i ostalih stereoizomera heksaklorcikloheksana, pp-\u27DDT-a i metabolita (pp-\u27DDE i pp-\u27DDD) i op-\u27DDT. Posebno je još analizirano 18 seruma majki i isto toliko seruma njihove djece koji su svi iz Zagreba. U uzorcima smo dokazali prisutnost samo Gama-HCH (Lindan). Alfa-HCH, pp-\u27DDE, op-\u27DDT, pp-\u27DDD i pp-\u27DDT. Koncentracije nađenih insekticida mnogo su veće u mlijeku dojilja nego u serumima. U serumima djece bilo je manje samo pp-\u27DDE i pp-\u27DDT nego u serumima njihovih majki. Uzorci seruma dojilja iz Zaboka i okolnih mjesta, hospitaliziranih u Zaboku i serumi dojilja iz Bjelovara hospitaliziranih u Zagrebu (N = 27) sadržavaju više navedenih insekticida nego uzorci seruma dojilja s područja Zagreba (N = 18).Milk samples obtained from 27 hospitalized lactating women and an equal number of sera from the same women were examined for residues of chlorinated hydrocarbon insecticides: aldrin, dieldrin, endrin, heptachlor, heptachlorepoxide, lindan and other steroisomers of hexachlorcyclohexane, pp\u27DDT and its metabolites (pp\u27-DDE, pp\u27-DDD) and op\u27-DDT. Additional 18 samples of mother\u27s sera and an equal number of their children\u27s sera were examined separately. The aim was to find out whether there is a correlation between the pesticide residues in mother\u27s serum and mother\u27s milk and in the serum of the mother and her child. The insecticides were determined according to the procedure used by the US Food and Drug Administration (4). Chlorinated hydrocarbon insecticides in the serum were examined with the method described by Wyllie and coworkers (5). In all samples only the presence of a-HCH, y-HCH, pp\u27-DDE, op\u27-DDT, pp\u27-DDD and pp\u27-DDT could be demonstrated. The concentration ratio between mother\u27s milk and serum was between 4 and 11. The concentration ratio between mother\u27s and child\u27s serum was below 1 except for pp\u27-DDE and pp\u27-DDT

Distinguishing “Through-Space” from “Through-Bonds” Contribution in Indirect Nuclear Spin–Spin Coupling: General Approaches Applied to Complex <i>J</i>_PP and <i>J</i>_PSe Scalar Couplings

We present herein two complementary theoretical approaches for analyzing the transmission pathways of indirect nuclear spin–spin couplings in high-resolution nuclear magnetic resonance. This phenomenon is notably conceptually poorly understood in complex experimental situations in which both nonbonded [“through-space” (TS)] and more “classical” bonding (“through-bond”) spin–spin coupling pathways are potentially involved. The computational approaches we propose allow the visualization and discussion of individual transmission pathways and estimation of their relative weight from numerical contributions to the spin–spin coupling constant J-value. The first approach is based on the analysis of contributions limited to occupied molecular orbitals [focused on occupied molecular orbitals (FOMO)]. The second approach encompasses the consideration of both occupied and vacant orbitals [global molecular orbital contributions (GMOC)], and, besides the contributions from individual pathways, also considers their cross contributions. Both approaches are applicable to large systems with complex interactions of nuclear magnetic moments. Herein, we have first applied the FOMO and GMOC computational approaches to simple diphosphine models and then extended the analysis to JPP and JPSe experimentally measured in a constrained selenated (diphosphino)­naphthalene compound. The new computational tools contributed evidence for the importance of the single lone pair not only from phosphorus but also from selenium in TS spin–spin transmission. It evidenced and modeled for the first time the existence of spin–spin transmission pathways mixing classical covalent bonding parts with a lone pair overlap of proximate heteroatoms (P and Se)

The Effect of Lewis Bases on the ¹³C NMR of Iodoalkynes

In Lewis-basic solvents, alkynyl carbons bonded to iodine have chemical shifts approximately 12−15 ppm higher in frequency than the corresponding shifts in CDCl3. We offer computational evidence that this solvent effect comes directly from polarization of the iodoalkyne triple bond. Hartree−Fock and Density Functional Theory calculations reproduce the change in chemical shift for a gas-phase complex between the iodoalkyne and dimethyl sulfoxide as Lewis base. The amount of spin−orbit coupling from the adjacent iodine does not change appreciably in the complex, according to the calculations

Quantum Chemical Investigation of Hyperfine Coupling Constants on First Coordination Sphere Water Molecule of Gadolinium(III) Aqua Complexes

Hyperfine interactions (HFI) on the nuclei of the first coordination sphere water molecules in a model [Gd(H2O)8]3+ aqua complex and in the magnetic resonance imaging contrast agent [Gd(DOTA)(H2O)]- were studied theoretically. Density functional theory (DFT) calculations combined with classical molecular dynamics (MD) simulations have been used in order to take into account dynamic effects in aqueous solution. DFT relativistic calculations show a strong spin-polarization of the first coordination sphere water molecules. This spin-polarization leads to a positive 17O isotropic hyperfine coupling constant (Aiso(17O) = 0.58 ± 0.11 MHz) and to a significant increase of the effective distance (〈reff(Gd−O)〉 = 2.72 ± 0.06 Å) of dipolar interaction compared to the mean internuclear distance (〈r(Gd−O)〉 = 2.56 ± 0.06 Å) obtained from the MD trajectory of [Gd(DOTA)(H2O)]- in aqueous solution. The point-dipole model for anisotropic hyperfine interaction overestimates therefore the longitudinal relaxation rate of the 17O nucleus by ∼45%. The 1H isotropic hyperfine coupling constant of the bound water molecule is predicted to be very small (Aiso(1H) = 0.03 ± 0.02 MHz), and the point-dipole approximation for first coordination sphere water protons holds. The calculated hyperfine parameters are in good agreement with available experimental data

Calculations of the EPR <b>g</b>-tensor using unrestricted two- and four-component relativistic approaches within the HF and DFT frameworks

Approaches and programs for calculations of the EPR g-tensor in the framework of the two- and four-component methods are still very rare. There are three main reasons for this: the wider community's unawareness of the importance of second- and higher order spin–orbit effects on the g-tensor, the methodological problems associated with performing such calculations and the lack of understanding of these problems. This paper reports on the implementation of a method for calculation of the g-tensor in the framework of the relativistic unrestricted two- and four-component Hartree–Fock and density functional theory approaches based on the Kramers pair formalism. This implementation allows us to analyse problems which arise when the g-tensor is calculated via Kramers pairs in the unrestricted framework.</p

Density Functional Calculations of Electronic g-Tensors for Semiquinone Radical Anions. The Role of Hydrogen Bonding and Substituent Effects

A recently developed density functional approach has been used to carry out a systematic computational study of electronic g-tensors for a series of 1,4-semiquinone radical anions. Good agreement with high-field EPR data in frozen 2-propanol is achieved only after taking into account the significant reduction of g-tensor anisotropy caused by hydrogen bonding to solvent molecules. The comparison of various model systems for the first solvation shell suggests two hydrogen bonds from 2-propanol molecules to each of the carbonyl groups of the radical anions, and one additional hydrogen bond to each of the methoxy groups in ubiquinone systems. 2-Propanol makes stronger hydrogen bonds than water and thus influences g-tensor anisotropy more strongly. Substituent effects at the semiquinone are reproduced quantitatively by the calculations. The g-tensor anisotropy is influenced significantly by the conformations of methyl and methoxy substituents, with opposite contributions. Analyses and interpretations of the interrelations between structure, bonding, and spectroscopic data are provided. The relevance of the computational results for the EPR spectroscopy of semiquinone radical anions in photosynthetic reaction centers is discussed

<b>g</b> Tensor and Spin Density of the Modified Tyrosyl Radical in Galactose Oxidase: A Density Functional Study

The influence of ortho sulfur substitution in the modified tyrosyl radical in apo-galactose oxidase on the g tensor and the spin-density distribution has been studied by calculations on various model systems using an accurate DFT approach. Computed g tensors agree well with experimental observation, and they are intermediate between the extremely large substituent effect found in a previous DFT study and the very small changes found in MCSCF calculations. The origin of the substituent effects has been studied by fragment analyses of the spin−orbit/orbital-Zeeman g-tensor contributions, and it is discussed in relation to the spin-density distributions. The influence of hydrogen bonding on g tensors is studied by appropriate model complexes with water. Further calculations on radicals including heavier chalcogen substituents XH (X = O, S, Se, Te) predict very large gx and gy components with selenium- and tellurium-substituted systems due to large, direct substituent spin−orbit contributions. In view of an unexpectedly large gauge dependence of the g-tensor orientation in several cases, a recently developed implementation of gauge-including atomic orbitals (GIAO) has been applied

Indirect Nuclear ¹⁵N–¹⁵N Scalar Coupling through a Hydrogen Bond: Dependence on Structural Parameters Studied by Quantum Chemistry Tools

NMR spin–spin couplings through a hydrogen bond in the free-base and protonated forms of the complete series of [¹⁵N₂]-N-methylated 1,8-diaminonaphthalenes have been analyzed using quantum chemistry tools. The dominating role of the overlap of the coupling pathway orbitals has been demonstrated. The correlation of the sum of the ¹³C NMR shifts of the naphthalene ring C­(1,8) carbons directly attached to the interacting nitrogens with the <i>J</i>(N–N) values and the degree of methylation found earlier by G. C. Lloyd-Jones et al. [Chem.Eur. J. 2003, 9, 4523] have been reexamined. It has been found that the correlations of <i>J</i>(N–N) and [Δ∑C_1,8] with the degree of methylation have different reasons. While the former is mostly connected with the structural changes due to the solvent effect, the latter is attributed to the changes in the paramagnetic contributions from the C–N and C–C bonds caused by the replacement of a hydrogen by a methyl group

Density Functional Calculations of Electronic g-Tensors for Semiquinone Radical Anions. The Role of Hydrogen Bonding and Substituent Effects

A recently developed density functional approach has been used to carry out a systematic computational study of electronic g-tensors for a series of 1,4-semiquinone radical anions. Good agreement with high-field EPR data in frozen 2-propanol is achieved only after taking into account the significant reduction of g-tensor anisotropy caused by hydrogen bonding to solvent molecules. The comparison of various model systems for the first solvation shell suggests two hydrogen bonds from 2-propanol molecules to each of the carbonyl groups of the radical anions, and one additional hydrogen bond to each of the methoxy groups in ubiquinone systems. 2-Propanol makes stronger hydrogen bonds than water and thus influences g-tensor anisotropy more strongly. Substituent effects at the semiquinone are reproduced quantitatively by the calculations. The g-tensor anisotropy is influenced significantly by the conformations of methyl and methoxy substituents, with opposite contributions. Analyses and interpretations of the interrelations between structure, bonding, and spectroscopic data are provided. The relevance of the computational results for the EPR spectroscopy of semiquinone radical anions in photosynthetic reaction centers is discussed

Density Functional Calculations of Electronic <i>g</i>-Tensors Using Spin−Orbit Pseudopotentials and Mean-Field All-Electron Spin−Orbit Operators

Modern density-functional methods for the calculation of electronic g-tensors have been implemented within the framework of the deMon code. All relevant perturbation operators are included. Particular emphasis has been placed on accurate yet efficient treatment of the two-electron spin−orbit terms. At an all-electron level, the computationally inexpensive atomic mean-field approximation is shown to provide spin−orbit contributions in excellent agreement with the results obtained using explicit one- and two-electron spin−orbit integrals. Spin−other−orbit contributions account for up to 25−30% of the two-electron terms and may thus be non-negligible. For systems containing heavy atoms we use a pseudopotential treatment, where quasirelativistic pseudopotentials are included in the Kohn−Sham calculation whereas appropriate spin−orbit pseudopotentials are used in the perturbational treatment of the g-tensors. This approach is shown to provide results in good agreement with the all-electron treatment, at moderate computational cost. Due to the atomic nature of both mean-field all-electron and pseudopotential spin−orbit operators used, the two approaches may even be combined in one calculation. The atomic character of the spin−orbit operators may also be used to analyze the contributions of certain atoms to the paramagnetic terms of the g-tensors. The new methods have been applied to a wide variety of species, including small main group systems, aromatic radicals, as well as transition metal complexes