Unfolding mechanism of PHD2 as a vital protein: all-atom simulation approach

Prolyl hydroxylase domain 2 containing protein (PHD2) is a central protein in regulation of cellular response to hypoxia. This protein controls the responses of cell to oxygen level via the regulation of hypoxia inducible factor (HIF) stability. HIF induces the expression of many genes, especially ones orchestrate angiogenesis. There are some reports that mentioned in some tumor types the level of HIF is high in spite of the presence of wild-type PHD2 and normoxic environment. Therefore, the possibility of PHD2 misfolding in some cancer cells arises. Studying such important protein unfolding pathway is insightful for possible therapeutic approaches. In this study, the unfolding pathway of PHD2 illustrates utilizing molecular dynamics simulation of protein thermal denaturation. Based on current study results, we represent the possible mechanisms of PHD2 unfolding in detail. The possible intermediates of PHD2 thermal unfolding are characterized, and the most venomous state of its unfolding pathway is introduced.     

A selective electromembrane extraction of uranium (VI) prior to its fluorometric determination in water

A novel method for the selective electromembrane extraction (EME) of U⁶⁺ prior to fluorometric determination has been proposed. The effect of extraction conditions including supported liquid membrane (SLM) composition, extraction time and extraction voltage were investigated. An SLM composition of 1% di-2-ethyl hexyl phosphonic acid in nitrophenyl octyl ether (NPOE) showed good selectivity, recovery and enrichment factor. The best performance was achieved at an extraction potential of 80 volts and an extraction time of 14 minutes Under the optimized conditions, a linear range from 1 to 1000 ng mL⁻¹ and LOD of 0.1 ng mL⁻¹ were obtained for the determination of U⁶⁺. The EME method showed good performance in sample cleanup and the reduction of the interfering effects of Mn²⁺, Zn²⁺, Cd²⁺, Ni²⁺, Fe³⁺, Co²⁺, Cu²⁺, Cl⁻ and PO₄³⁻ ions during fluorometric determination of uranium in real water samples. The recoveries above 54% and enrichment factors above 64.7 were obtained by the proposed method for real sample analysis.     

Ultra‐Trace Silver Determination in Biological and Water Samples by Electrothermal Atomic Absorption Spectrometry after Electrodeposition on a Graphite Probe

A rapid and simple procedure was developed for selective and sensitive determination of ultra‐trace silver in biological and environmental samples using the electrodeposition on a graphite probe modified with palladium followed by electrothermal atomic absorption spectrometry. Several experimental parameters for the electrodeposition, such as deposition potential, electrolyte concentration, pH of solution and deposition time were optimized. The calibration graph after preconcentration was linear in the range of 10‐250 ngL^?1 with correlation coefficient of 0.9989 under the optimum conditions for procedure. The limits of detection (LOD) and quantification (LOQ) base on (3σ) and (10σ) were 2.8 ngL^?1 and 9.4 ngL^?1 respectively. Related standard deviation (RSD) for eight replicate measurements of 100 ngL^?1 silver was 4.3%. Samples were digested completely in a closed microwave digestion system using only perchloric acid, and interference owing to various cations was also investigated. The proposed procedure was successfully applied to determine silver in blood, urine and some environmental samples with satisfactory analytical results.     

High‐Efficiency Conversion of Trimethylsilyl Ethers to Their Corresponding Ethers using Carbon‐Based Solid Acid as a New Catalyst in Heterogeneous Mixtures

Carbon‐based solid acid was used as a new catalyst for conversion of trimethylsilyl ethers to their corresponding ethers in heterogeneous mixtures. The experiments were done moderately at room temperature, and high yields in suitable times were obtained under these conditions.     

Oxidation of 1,4-Dihydropyridines under Mild and Heterogeneous Conditions

A combination of NaHSO₄.H₂O and NaNO₂ in the presence of wet SiO₂ was used as an effective oxidizing agent for the oxidation of dihydropyridines to their corresponding pyridine derivatives at room temperature with excellent yields.     

Synthesis of New and Novel N-Protected 1-Aminoalkyl-2-naphthol Derivatives

A series of three-component reactions has been carried out using HClO₄-SiO₂ as a versatile heterogeneous catalyst. A series of new and novel N-protected 1-aminoalkyl-2-naphthol derivatives have been prepared under thermal solvent-free reaction conditions. In all cases, the reaction conditions were very simple and high-yielding.     

Synthesis of New 2-Aryl Substituted 2,3-Dihydroquinazoline-4(1H)-ones Under Solvent-Free Conditions,Using Molecular Iodine as a Mild and Efficient Catalyst

A simple, inexpensive, and efficient one-pot synthesis of 2,3-dihydroquinazoline-4(1H)-one derivatives under solvent-free conditions using a catalytic amount of iodine with excellent product yields is reported. This methodology provides easy, quantitative access to various 2,3-dihydroquinazoline-4(1H)-one derivatives, using commercially available iodine as a catalyst.     

Electronic,spectra, and spin orbit interaction for FrAr van der Waals system

The potential energy curves and spectroscopic constants of the ground and many excited states of the FrAr van der Waals system have been determined using a one‐electron pseudopotential approach. The Fr⁺ core and the electron–Ar interactions are replaced by effective potentials. The Fr⁺Ar core–core interaction is incorporated using the accurate CCSD(T) potential of Hickling et al. (Phys. Chem. Chem. Phys. 2004, 6, 4233). This approach reduces the number of active electrons of the FrAr van der Waals system to only one valence electron, which permits the use of very large basis sets for the Fr and Ar atoms. Using this technique, the potential energy curves of the ground and many excited states are calculated at the self consistent field (SCF) level. In addition, the spin–orbit interaction is also considered using the semiempirical scheme for the states dissociating into Fr (7p) and Fr (8p). The FrAr system is not studied previously and its potential interactions, spectroscopic constants and dipole functions are presented here for the first time. Furthermore, we have predicted the X²Σ⁺–A²Π_1/2, X²Σ⁺–AΠ_3/2, X²Σ⁺–B²Σ_1/2⁺, X²Σ⁺–3²Π_1/2, X²Σ⁺–3²Π_3/2, and X²Σ⁺–5²Σ_1/2⁺ absorption spectra. © 2012 Wiley Periodicals, Inc.     

Bulk polymer nanoparticles containing a tetrakis(3-hydroxyphenyl)porphyrin for fast and highly selective separation of mercury ions

We report on the synthesis of polymeric nanoparticles (PNPs) containing a tetrakis(3-hydroxyphenyl)porphyrin, and their use for the separation of mercury(II) ion. The PNPs were prepared by bulk polymerization from methacrylic acid (the monomer), ethyleneglycol dimethacrylate (the cross-linker), 2,2′-azobisisobutyronitrile (the radical initiator) and the mercury(II) complex of 5,10,15,20-tetrakis(3-hydroxyphenyl)-porphyrin. The Hg(II) ion was then removed by treatment with dilute hydrochloric acid. The PNPs were characterized by colorimetry, FT-IR spectroscopy, and scanning electron microscopy. The material is capable of binding Hg(II) from analyte samples. Bound Hg(II) ions can be eluted with dilute nitric acid and then quantified by cold vapor AAS. The extraction efficiency, the effects of pH, preconcentration and leaching times, sample volume, and of the nature, concentration and volume of eluent were investigated. The maximum adsorption capacity of the PNPs is 249 mg g^?1, the relative standard deviation of the AAS assay is 2.2 %, and the limit of detection (3σ) is 8 ng.L^?1. The nanoparticles exhibit excellent selectivity for Hg(II) ion over other metal ions and were successfully applied to the selective extraction and determination of Hg(II) ion in spiked water samples.

Anodic stripping voltammetry of silver(I) using a carbon paste electrode modified with multi-walled carbon nanotubes

We describe a silver(I)-selective carbon paste electrode modified with multi-walled carbon nanotubes and a silver-chelating Schiff base, and its electrochemical response to Ag(I). Effects of reduction potential and time, accumulation time, pH of the solution and the stripping medium were studied by differential pulse anodic stripping voltammetry and optimized. The findings resulted in a method for the determination of silver over a linear response range (from 0.5 to 235 ng?mL^?1) and with a detection limit as low as 0.08 ng?mL^?1. The sensor displays good repeatability (with the RSD of ±?2.75 % for 7 replicates) and was applied to the determination of Ag(I) in water samples and X-ray photographic films.