Thermochemical properties of some vinyl chloride-induced DNA lesions: detailed view from NBO & AIM analysis

Etheno-damaged DNA adducts such as 3,N ⁴-ethenocytosine, N ²,3-ethenoguanine, and 1,N ²-ethenoguanine are associated with carcinogenesis and cell death. These inevitable damages are counteracted by glycosylase enzymes, which cleave damaged nucleobases from DNA. Escherichia coli alkyl purine DNA glycosylase is the enzyme responsible for excising damaged etheno adducts from DNA in humans. In an effort to understand the intrinsic properties of these molecules, we examined gas-phase acidity values and proton affinities (PA) of multiple sites of these molecules as well as equilibrium tautomerization and base pairing properties by quantum mechanical calculations. We also used calculations to compare the acidic and basic properties of these etheno adduct with those of the normal bases—cytosine and guanine nucleobases. We hypothesize that alkyl DNA glycosylase may cleave certain damaged nucleobases as anions and that the active site may take advantage of a nonpolar environment to favor deprotonated cytosine or guanine as a leaving group versus damaged nucleobases.     

Polypyrrole/polyamide electrospun-based sorbent for microextraction in packed syringe of organophosphorous pesticides from aquatic samples

A novel method based on microextraction in packed syringe (MEPS) as sample preparation technique coupled off-line with gas chromatography-mass spectrometry was developed using electrospun nanofibers as sorbent. For electrospinning of polypyrrole/polyamide-based nanofiber, a homogeneous solution containing nylon 6, ferric chloride and pyrrole monomer was prepared and then was drawn into a 2.5-mL syringe. By applying a voltage of 13 kV between the needle of the syringe and an aluminum-foil collector, the nanofibers could be formed on the surface of the collector. The prepared sheet was used as the sorbent for MEPS to analyze some selected organophosphorous pesticides. Important parameters influencing the extraction and desorption processes were optimized. Limits of detection were in the range of 0.04-0.1 ng/mL using time scheduled selected ion monitoring mode, and the relative standard deviation (RSD %) values with four replicates were in the range of 3.7-11.8% at a concentration level of 5 ng/mL. The linearity of the method was in the range of 0.5-500 ng/mL for diazinon and fenithrothion and 0.5-200 ng/mL for the rest of the analytes. The developed method was successfully applied to Zayandeh-roud river water samples, whereas the matrix factors were in the range of 0.87-0.98.     

Vibrational circular dichroism spectroscopy of two chiral binaphthyl diphosphine ligands and their palladium complexes in solution

BINAP (2,2'-diphenylphosphino-1,1'-binaphthyl) is a unique binaphthyl diphosphine ligand with axial chirality. The palladium complexes of BINAP and of its derivative TOLBINAP have found extensive applications in the field of asymmetric syntheses. The conformational changes in the BINAP and TOLBINAP ligands before and after coordination with palladium have been investigated using density functional theory, vibrational absorbance (VA) and vibrational circular dichroism (VCD) spectroscopy. VA and VCD spectra of these two chiral ligands and their corresponding palladium complexes have been recorded in CDCl(3) solution. Extensive conformational searches have been carried out for both the ligands and the associated palladium complexes. Coordination with palladium has been found to introduce structural rigidity to the ligands. The calculated VA and VCD spectra of the ligands and complexes in the gas phase show substantial differences to the experimental data. Incorporation of the implicit polarisable continuum solvation model has provided much better agreement between theory and experiment, especially for the complexes, allowing clear identification of the species and conformations. This and the high specificity of VCD spectral signatures to chirality and to conformations suggest the potential applications of VCD spectroscopy for following these important catalytic species in solution reactions directly.     

Anti-cholinergic effect of Zataria multiflora Boiss on guinea pig tracheal chains

The effects of three concentrations of aqueous-ethanolic extract, 10?nM atropine and saline on muscarinic receptors were tested on two groups of non-incubated (group 1; n?=?7) and incubated tracheal chains with propranolol and chlorpheniramine (group 2; n?=?6). The EC?? of higher concentration of the extract (2?μg?mL?1) in group 2 was significantly greater than those of group 1 (p?相似文献   

Influence of Y2Cu2O5 nanoparticles doping on superconducting properties of YBa2Cu3O7-δ

ABSTRACT

The blue phase of YBa₂Cu₃O_{7- δ} (YBCO) family, Y₂Cu₂O₅ (Y202) nanoparticles were prepared and doped into (YBCO) superconductor and the effect of doping on critical current density and critical temperature was investigated. Y202 nanoparticles with particle sizes of 47, 107 and 206?nm were prepared by a sol–gel combustion method and added into the YBCO superconductor by 0.5–2?wt.%. XRD and scanning electron microscope measurements were used to characterize the samples. The measurement of critical current density at 77?K revealed that the doped superconductors had larger critical current density compared to the undoped superconductors. For a fixed dopant concentration, by increasing the size of nanoparticles, the J_c was increased. For the samples including 0.5?wt.% of nanoadditives, J_c was higher. The highest critical current density of 137?A/cm² was measured for the superconductors containing 0.5?wt.% of 206?nm Y202 nanoparticles. Also, by increasing the nanoparticles concentration, the T_c was reduced.     

Inelastic effect of electron–phonon interactions in tunnelling magnetoresistance of a single metallofullerene

The effects of elastic and inelastic electron–phonon interactions on current–voltage characteristic and tunnelling magnetoresistance (TMR) of Li@C₅₉X (X = N, B) molecule that is coupled to two ferromagnetic electrodes was investigated using the non-equilibrium Green's function (NEGF) method. Our results by taking also into consideration spin degrees of freedom (excluding spin-mixing effects) indicate that the presence of inelastic electron–phonon interaction polaron formation increases current and shifts the TMR behaviour to higher values. Also, an increase of two orders of magnitude observed in current for Li@C₅₉B compared to C₆₀.     

Density and birefringence of a highly stable α,α,β-trisnaphthylbenzene glass

Spectroscopic ellipsometry has been used to understand the properties of α,α,β-trisnaphthylbenzene (ααβ-TNB) glasses vapor-deposited at a substrate temperature of 295 K (0.85 T(g)). In a single temperature ramping experiment, a range of properties of the as-deposited glass can be measured, including density, fictive temperature, onset temperature, thermal expansion coefficient, and birefringence. The vapor-deposited ααβ-TNB glass is 1.3% more dense than the ordinary glass prepared by cooling at 1 K/min, is found to be birefringent, has a fictive temperature 35 K below that of the ordinary glass, and an onset temperature 20 K above that of the ordinary glass. The thermal expansion coefficient of the vapor-deposited ααβ-TNB glass is 14% lower than that of the ordinary glass, indicating that lower portions of the potential energy landscape have more harmonic potential minima than the parts accessible to the ordinary glass.     

Highly efficient and convenient Strecker reaction of carbonyl compounds and amines with TMSCN catalyzed by MCM-41 anchored sulfonic acid as a recoverable catalyst

MCM-41 anchored sulfonic acid (MCM-41–SO₃H) was found to be a highly efficient and recoverable heterogeneous catalyst for the three-component Strecker reaction of aldehydes or ketones and diverse amines using trimethylsilyl cyanide (TMSCN) to afford the corresponding α-amino nitriles under mild conditions in high to quantitative yields. The simple experimental procedure along with easy recovery and reusability of the catalyst has led to development of a clean and environmentally friendly approach for the synthesis of α-amino nitriles.     

Serial factorizations of right ideals

In a Dedekind domain D, every non-zero proper ideal A factors as a product $A=P_1^{t_1}?P_k^{t_k}$ of powers of distinct prime ideals $P_i$. For a Dedekind domain D, the D-modules $D/P_i^{t_i}$ are uniserial. We extend this property studying suitable factorizations $A=A_1\dots A_n$ of a right ideal A of an arbitrary ring R as a product of proper right ideals $A_1,\dots ,A_n$ with all the modules $R/A_i$ uniserial modules. When such factorizations exist, they are unique up to the order of the factors. Serial factorizations turn out to have connections with the theory of h-local Prüfer domains and that of semirigid commutative GCD domains.     

Polarized neutron scattering investigation of excitations at low momentum transfer in liquid Ga: The mystery continues

New polarized neutron scattering experiments are presented on liquid gallium just above the melting transition of 303 K in order to shed light on the origin of the observed increased Ga cross-section at small scattering angles that has previously been reported in the literature. Our polarized neutron scattering experiments show that this increased cross-section cannot be linked to any magnetic or incoherent process, a linkage that was needed to justify the interpretation of this broad mode as being part of the cage-diffusion process. Instead, the increased cross-section has to be attributed to a coherent process, in violation of the measured sum-rules.