Open Access Published by De Gruyter Open Access

Volume 5 Issue 3

September 2007

Issue of Open Chemistry

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Contents
Journal Overview

Open Access May 20, 2007

Molecular dynamics simulations of potassium channels

Carmen Domene

Page range: 635-671

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Abstract

Despite the complexity of ion-channels, MD simulations based on realistic all-atom models have become a powerful technique for providing accurate descriptions of the structure and dynamics of these systems, complementing and reinforcing experimental work. Successful multidisciplinary collaborations, progress in the experimental determination of three-dimensional structures of membrane proteins together with new algorithms for molecular simulations and the increasing speed and availability of supercomputers, have made possible a considerable progress in this area of biophysics. This review aims at highlighting some of the work in the area of potassium channels and molecular dynamics simulations where numerous fundamental questions about the structure, function, folding and dynamics of these systems remain as yet unresolved challenges.

Open Access June 9, 2007

Mechanistic studies on the effect of veratryl alcohol on the lignin peroxidase catalyzed oxidation of pyrogallol red in reversed micelles

Jing Lan, Xirong Huang, Ming Hu, Weifeng Liu, Yuezhong Li, Yinbo Qu, Peiji Gao

Page range: 672-687

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Abstract

The lignin peroxidase (LiP) catalyzed oxidation of pyrogallol red (PR) in the absence and presence of veratryl alcohol (3,4-dimethoxybenzyl alcohol, VA) was carried out in bis (2-ethylhexyl) sulfosuccinate sodium (AOT)/ polyoxyethylene lauryl ether (Brij30) reversed micelles to elucidate the role of VA. Results indicated that VA could accelerate the LiP catalyzed oxidation of PR, especially at low H2O2 concentrations. Unlike in bulk aqueous medium, the protection of LiP by VA in the present medium was relatively unsubstantial, even at high H2O2 concentrations. Analysis of data from a series of experiments showed that the enhancement of the PR oxidation caused by VA was mainly due to the indirect oxidation of PR by VA+∙ from the LiP catalyzed oxidation of VA. It was also found that at the same protector concentration (40 μM), VA (the physiological substrate of LiP) was less effective than PR (a phenolic compound) in protecting LiP from the H2O2 derived inactivation. This novel phenomenon deserves further study.

Open Access April 26, 2007

Indolyl substituted 4-oxobut-2-enoic acids. Synthesis and aza-Michael additions

Dušan Berkeš, Anna Koren̆ová, Peter Šafár̆, Helena Horváthová, Nadežda Prónayová

Page range: 688-705

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Abstract

The synthesis of three new substituted 4-hetereoaryl-4-oxobut-2-enoic acids with indole ring substitutedin positions 3-, 5- and 7- is described. The addition of these Michael acceptors to 4-(1-phenylsulphonylpyrrol-3-yl)-4-oxobut-2-enoic acid in conjugate addition was explored using both racemic and chiral amines. In tandem with the crystallization-induced asymmetric transformation (CIAT) protocol the effective methodology for the synthesis of enantiomerically highly enriched substituted 2-amino-4-heteroaryl-4-oxobutanoic acids as multifunctional homotryptophan analogues was developed.

Open Access April 26, 2007

Thermal synthesis and characterization of AlχLa1-χ P3O9

Petr Bělina, Petra Šulcová, Miroslav Trojan, Pavel Mazurek

Page range: 706-714

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Abstract

New binary lanthanum-aluminum triphosphates were synthesized by thermal-condensation method from H3PO4, La2O3 and Al(OH)3. These pigments could be potentially used as special inorganic pigments; their corrosion-inhibition properties were widely studied. Synthesis conditions were determined on the basis of DTA and TG measurements. The products were also characterized by X-ray diffraction analysis. Physical properties — density by pycnometric method, particle size distribution, oil number and critical pigment volume concentration (CPVC), pH and specific conductivity of their aqueous extracts were also determined.

Open Access September 1, 2007

Esterification of palmitic acid with epichlorohydrin on anion exchange resin catalyst

Emil Muresan, Spiridon Oprea, Theodor Malutan, Mihai Vata

Page range: 715-726

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Abstract

The esterification reaction of palmitic acid with epichlorohydrin catalyzed by an anionic macroporous resin was studied. Purolite A-500 resin proved to be a very effective catalyst in the synthesis of 3-chloro-2-hydroxypropyl palmitate. The effects of certain parameters such as speed of agitation, catalyst particle size, catalyst loading, temperature, initial molar ratio between reactants on the rate of reaction were studied. It was found that the overall rate is intrinsically kinetically controlled. The structure of synthesized ester was confirmed by FTIR and 1H NMR analyses.

Open Access September 1, 2007

Polyaniline-polypyrrole coating for solid phase microextraction

Vida Vickackaite, Vilma Ciuvasovaite

Page range: 727-738

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Abstract

A procedure for direct electrochemical deposition of polyaniline-polypyrrole blend coating on the surface of stainless steel wire was suggested. Incorporation of polyaniline and polypyrrole into the blend coating was confirmed by infrared spectroscopy. Key parameters (pyrrole, aniline, dopant and sulphuric acid concentrations and deposition potential) influencing the coating’s mechanical stability and surface homogeneity were optimised and thermostability of the coating was investigated. A possibility to apply the coating as a new fibre for solid phase microextraction was demonstrated. The coating showed better selectivity toward aromatic, hydrophobic compounds.

Open Access June 9, 2007

On the determination of lead in wine by electrothermal atomic absorption spectrometry

Irina Karadjova, Julijana Cvetković, Trajče Stafilov, Sonja Arpadjan

Page range: 739-747

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Abstract

The parameters of analytical procedures developed for direct ETAAS determination of Pb in wine are discussed. Atomic absorption spectrometers based on transversal and longitudinal Zeeman effect, wall and integrated platform atomization with two main approaches: (i) measurements in the presence of modifier and (ii) measurements without using any modifier are compared. The optimal temperature programs are defined according to the pre-treatment and atomization curves constructed in the presence of different types of wines. For all investigated instrumental systems, 1:1 dilution of wine sample with 0.2 mol L−1 HNO3 is recommended. Matrix interferences observed, call for standard addition calibration method for Pb quantification in wines. The detection limit (3σ) achieved for wine diluted in the ratio of 1:1 varied from 0.8 to 1.9 μg L−1 depending on the instrument used. The relative standard deviation for the concentration range of 10 to 80 μg L−1 Pb in wine is typically between 4–8%. The accuracy of the analytical procedures recommended was confirmed by comparing the results obtained with those found for wine samples previously digested with HNO3-H2O2 mixture, by added/found method and by parallel analysis using different instruments. A total of 66 wine samples from different regions of Macedonia were analyzed.

Open Access September 1, 2007

Contact angles of protein black foam films under dynamic and equilibrium conditions

Michail Nedyalkov, Caroline Sultanem, Jean-Jacque Benattar

Page range: 748-765

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Abstract

The contact angles of protein Newton black foam films from ALG (alpha-lactalbumin), BLG (beta-lactoglobulin) and BSA (bovine serum albumin) are measured here within. The measurements are carried out under dynamic and equilibrium conditions. For all proteins, a strong hystheresis effect of the contact angle is observed under dynamic conditions. An attempt is made to explain these results by the slow adsorption and desorption kinetics of the protein bilayers and by the dynamic structure and the rheology of the protein network forming the bubble walls. In addition, we propose a modification of the experimental device reported previously for contact angle measurements of large flat films in equilibrium. The advantages of this method are discussed in detail. Some shortcomings (precision, reproducibility) of this preliminary variant of the device in this initial stage of its application, do not allow one to draw reliable conclusions about the interactions of these films. Some improvements of the measurement quality are proposed.

Open Access September 1, 2007

Method validation in quantitative electrochemical analysis of colchicine using glassy carbon electrode

Ede Bodoki, Robert Săndulescu, Liviu Roman

Page range: 766-778

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Abstract

A cathodic differential pulse voltammetric determination of colchicine was validated using a glassy carbon electrode in HClO4/H3PO4 0.01 M. Colchicine gives an irreversible, diffusion-controlled peak at −862 mV vs. Ag/AgCl reference electrode. The cathodic peak is strongly influenced by a more alkaline environment with a shift towards more negative potentials. Method optimization was carried out in parallel for three types of electrodes (glassy carbon, mercury film and bismuth film coated glassy carbon). The cathodic peak current is higher using film-coated electrodes, but shows poorer intra-day reproducibility and a longer analysis time due to film renewal. Thus, a bare glassy carbon electrode was used to determine colchicine in the concentration range of 2.4 − 50 μg mL−1 (R 2 = 0.9998, n = 5), with a calculated detection limit of 0.80 μg mL−1. The proposed method was characterized according to ICH Harmonized Tripartite Guidance Q2(R1) by validation parameters (selectivity, linearity, accuracy, fidelity, limit of detection, limit of quantification) and it was successfully applied for the determination of colchicine from tablets, without the interference of the excipients. The method’s performances were evaluated and compared with both a known polarographic method and the official quantitative spectrophotometric determination from the Romanian Pharmacopoeia, Xth edition, respectively.

Open Access April 26, 2007

Electrospinning of the hydrophilic poly (2-hydroxyethyl methacrylate) and its copolymers with 2-ethoxyethyl methacrylate

Martin Přádný, Lenka Martinová, Jiří Michálek, Tat’ána Fenclová, Eva Krumbholcová

Page range: 779-792

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Abstract

The goal was to electrospin 2-hydroxyethyl methacrylate — based biocompatible polymers and prepare submicron fibres (nanofibers) for biomedicinal applications. Syntheses of poly(2-hydroxyethyl methacrylate) (HEMA) and its copolymer with 2-ethoxyethyl methacrylate (EOEMA), and their characterization by viscometry and molecular weight are described. Their relation to electrospinning is discussed. Electrospinning of HEMA homopolymer from water-ethanol is successful for molecular weights 6.31 × 105 and 1.80 × 106 g/mol. Electrospinning of HEMA/EOEMA copolymers is feasible from ethanol.

Open Access April 26, 2007

Electron rectification through donor-acceptor-heterocyclics connected to cumulenic bridge: a computational study

J. Laxmikanth Rao

Page range: 793-812

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Abstract

Density Functional Theory (DFT) calculations and Frontier Molecular Orbital (FMO) analysis have been carried out at B3LYP/6-31G(d,p) level of theory on some Donor-Bridge-Acceptor (D-B-A) molecules for their electrical rectification behavior. The donor-acceptor-heterocyclics (D/A-heterocyclics) (namely thiophene, furan and pyrrole rings) are attached as donor and acceptors to the two ends of cumulenic bridge. FMO analysis indicates that the molecules having even number of double bonds in the bridge, possess a complete localization of the MOs i.e., the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) are localized on the donor and the acceptor side of the molecules respectively, and LUMO+1 is localized on the donor side, where as in case of odd number of double bonds in the bridge, both the HOMO and LUMOs are delocalized all over the molecule. The Potential Drop (PD) in the former case decreases as the number of double bonds increases in the bridge and due to the presence of the mutually orthogonal and noninteracting π-clouds, they can act as molecular rectifiers. For the molecules with the odd number of double bonds due to the low-lying LUMO delocalized all over the molecule, may find application as molecular wires in molecular electronics circuits.

Open Access May 2, 2007

Determination of diclofenac in pharmaceuticals and urine samples using a membrane sensor based on the ion associate of diclofenac with Rhodamine B

Zholt Kormosh, Iryna Hunka, Yaroslav Bazel, Andriy Laganovsky, Iryna Mazurenko, Nataliya Kormosh

Page range: 813-823

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Abstract

The potentiometric response characteristics of a diclofenac selective electrode, based on ion association in different plasticizers, were compared. The sensitivity, working range, detection limit and selectivity of membrane sensors demonstrated significant dependence on the type of plasticizers. The potentiometric unit presented a linear response toward diclofenac concentrations between 1 × 10−5 − 5 × 10−2 mol L−1, with slopes of approximately 60 mV dec−1, and exhibited a response time of 3 s. The potentiometric analysis of sodium diclofenac in pharmaceutical formulations was perfomed by the membrane electrode proposed and compared with the results of potentiometric titration given by the Pharmacopoeia of Ukraine.

Open Access September 1, 2007

Pyrrole thin films deposited on paper by pulsed RF plasma

Halil Şahin

Page range: 824-834

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Abstract

Attempts were made to plasma deposit an oriented π-conjugated polymer of pyrrole (Py) on paper surfaces in order to produce electrically conductive layers. The N/C atomic ratio of 0.13–0.24 was observed for all treatment conditions. This implies the nature of the deposition formed on the paper surface via pulsed plasma is different from that of pyrrole monomer. An increase in conductivity of all pyrrole-plasma treated papers was observed. The 50 W RF-power with 5 min plasma exposed paper sample shows 8.15 × 10−9 S·cm−1 conductivity. The conductivity measurements indicated a plasma-enhanced ring-opening reaction mechanism of pyrrole.

Open Access May 13, 2007

Adsorptive stripping voltammetric determination of the anti-inflammatory drug tolmetin in bulk form, pharmaceutical formulation and human serum

Amr Beltagi, Mona El-Attar, Enass Ghoneim

Page range: 835-845

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Abstract

The electro-reduction of tolmetin at the hanging mercury drop electrode was studied in different supporting electrolytes using cyclic voltammetry and square-wave stripping voltammetry techniques. Voltammograms of tolmetin exhibited a single well-defined 2-electron irreversible cathodic peak in media of pH C=O double bond of the analyte molecule. Adsorption of tolmetin onto the surface of the hanging mercury electrode was identified and each adsorbed tolmetin molecule was found to occupy an area of 0.23 nm2. A square-wave adsorptive cathodic stripping voltammetric procedure was described for the direct determination of tolmetin in bulk form and pharmaceutical formulation (Rumatol® capsules) with a limit of quantitation of 2 × 10−9 M and a mean percentage recovery of 98.35 ± 1.21% to 99.57 ± 1.23. Moreover, the described procedure was successfully applied for the direct assay of tolmetin in spiked human serum without pretreatment or extraction prior to the analysis while a quantitation limit of 5 × 10−9 M tolmetin was achieved.

Open Access May 20, 2007

Immobilization of soil mercury by colloidal sulphur in the laboratory experiment

Fyodor Kot, Vladimir Rapoport, Galina Kharitonova

Page range: 846-857

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Abstract

The results of the laboratory pot experiments on soil mercury (Hg) immobilisation with a non-toxic and price-reasonable agent — colloidal sulphur (S) water suspension, are presented. It was shown that fertilisation with small agrochemical doses of colloidal S reduces excess Hg effectively as follows: in interstitial waters by a factor 2 – 12 times for total Hg, and 22– 680 times for “reactive” Hg; in stems and leaves of oats – 7 – 22 times; and in moss bags, reflecting soil Hg degassing, 7 – 15 times, for the most heavily Hg-spiked soils. The results obtained allowed to conclude that the immobilization of Hg occurs through Hg binding to the newly formed S-bearing functional groups in humic acids and/or sulphides.

Open Access May 26, 2007

Heterobimetallic complexes containing iron (II) and hexa-coordinated organosilicon

Rajesh Malhotra, Jyoti Mehta, J. Puri

Page range: 858-867

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Abstract

Heterobimetallic complexes of the type R2Si(HL)Cl2 and R2SiL2 (where R = Me, Et, Ph; L = ferrocenyl aroylhydrazone) have been synthesized at 40 °C to 50 °C and at room temperature (25 °C), respectively, and characterized by elemental analysis, molar conductance, infrared and NMR (1H, 13C and 29Si) spectral data. The ligands behave as bidentate, coordinating through the azomethine nitrogen and the oxygen in the amidic and the imidic acid forms of the ligand at low temperature and at room temperature, respectively. The ligands and their organosilicon complexes have been evaluated for the antifungal activity against Alternaria alternata, Fusarium oxysporum and Rhizoctonia solani, as well as antibacterial activity against gram negative, Escherichia coli and gram positive, Bacillus subtilis, at 28 °C. Organosilicon complexes of ferrocenyl aroylhydrazone were found to be more potent than the parent ligands.

Open Access September 1, 2007

Simple method for calculating time dependence of individual radionuclide activities in decay series

Jiří Landa, Štefan Palágyi

Page range: 868-879

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Abstract

A rapid method for calculating the time dependence of activities of individual radionuclides in genetically coupled decay series has been proposed. The method is based on the mathematical procedure, in which the matrix method is used for calculating a set of decay equations given in the vector form. The developed method is computerized and uses the modern Scilab software. This simple method eliminates certain drawbacks of older methods used previously for this purpose and is applicable to even solve calculations which are not easily treatable with the older methods. Some practical examples of such calculations are presented. Moreover, the new method is universal and it also enables a more general approach to the problem of the calculation of decay series in nuclear chemistry.

Open Access September 1, 2007

Synthesis, anti-fungal activity evaluation and QSAR studies on podophyllotoxin derivatives

K. Anil Kumar, Sanjay Kumar Singh, B. Siva Kumar, Mukesh Doble

Page range: 880-897

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Abstract

The anti-fungal and cytotoxic activites of podophyllotoxin and seven C-4 substituted podophyllotoxin ester derivatives, viz: trans-cinnamyl, cis-cinnamyl, o-methoxy cinnamyl, dimethyl acrylyl, p-methoxy phenyl acetyl, 3,4-dimethoxy phenyl acetyl and 2,5-dimethoxy phenyl acetyl esters were evaluated on four fungi, viz: Macrophomina phaseolina, Fusarium oxysporum, Myrrothecium verrucarria and Asperigillus candidus, The podophyllotoxin derivatives were synthesised and their structures were elucidated. Quantitative structure activity relationships were developed between the activity of these compounds against the four fungi and molecular descriptors. The linear regression models developed had one to two descriptors. For all the cases the r 2 was in the range of 0.73 to 0.96, indicating good data fit and q 2 was in the range of 0.60 to 0.68, indicating that the predictive capabilities of the models were acceptable. Solvent accessible surface area (namely the partial positive solvent-accessible surface area), A log P, highest occupied molecular orbital and conformational energy were identified as important descriptors.

Open Access September 1, 2007

Voltammetric and potentiometric studies of some sulpha drug-Schiff base compounds and their metal complexes

M. Ghoneim, E. Mabrouk, A. Hassanein, M. El-Attar, E. Hesham

Page range: 898-911

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Abstract

The electrochemical behavior of some sulpha drug-Schiff bases at a mercury electrode was examined in the Britton-Robinson universal buffer of various pH values (2.5–11.7) containing 20% v/v) of ethanol using DC-polarography, cyclic voltammetry and controlled-potential electrolysis. The DC-polarograms and cyclic voltammograms of the examined compounds exhibited a single, 2-electron, irreversible, diffusion-controlled cathodic step within the entire pH range which is attributed to the reduction of the azomethine group-CH=N- to -CH2-NH-. The symmetry transfer coefficient (α) of the electrode reaction and the diffusion coefficient (D 0) of the reactant species were determined. The electrode reaction pathway of the compounds at the mercury electrode was suggested to follow the sequence: H+, e−, e−, H+. The dissociation constant of the sulpha drug-Schiff bases, the stability constant and stoichiometry of their complexes with various divalent transition metal ions (Mn2+, Co2+, Ni2+, Cu2+ and Zn2+) were determined potentiometrically at room temperature.

Open Access April 12, 2007

Molten solvent extraction behavior of palladium with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone at 60 °C

Bo Peng, Xiaojun Guo, Xuefen Mao, Jinzhang Gao

Page range: 912-921

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Abstract

The solvent extraction behavior of precious metal palladium with 1-phenyl-3-methyl-4-benzoyl-5-pyrazone (PMBP) into molten paraffin wax has been studied in the temperature range from 55 to 75 °C. The complex consisting of PMBP and palladium was extracted into molten wax phase in the pH range from 1.0 to 3.5 at 60 °C. The extraction efficiency was up to 97% at the experimental pH. The stoichiometry of the extracted species of palladium was determined on the basis of slope analysis method. The effects of time to achieve equilibrium, temperature, and extractant concentration on the extraction were discussed. The thermodynamic data indicate that the extraction is an endothermic reaction and the increase of temperature promotes the extraction of palladium into molten paraffin wax and the extraction of palladium with PMBP is entropy controlled at high temperatures.

About this journal

Open Chemistry is a peer-reviewed, open access journal that publishes original research, reviews, and communications in the fields of chemistry in an ongoing way. Our central goal is to provide a hub for researchers working across all subjects to present their discoveries, and to be a forum for the discussion of the important issues in the field.

There are no submission charges. In order to sustain the production of our fully-refereed open access journal, each article accepted for publication in Open Chemistry is subject to Article Processing Charges (APC).

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