Maher M. Hamed

Computational investigation and synthesis of a sol–gel imprinted material for sensing application of some biologically active molecules

A hybrid sol-gel material was molecularly imprinted with a group of neurotransmitters. Imprinted material is a sol-gel thin film that is spin coated on the surface of a glassy carbon electrode. Imprinted films were characterized electrochemically using cyclic voltammetry (CV) and the encapsulated molecules were extracted from the films and complementary molecular cavities are formed that enable their rebind. The films were tested in their corresponding template solutions for rebinding using square wave voltammetry (SWV). Computational approach for exploring the primary intermolecular forces between templates and hydrolyzed form of the precursor monomer, tetraethylorthosilicate (TEOS), were carried out using Hartree-Fock method (HF). Interaction energy values were computed for each adduct formed between a monomer and a template. Analysis of the optimized conformations of various adducts could explain the mode of interaction between the templates and the monomer units. We found that interaction via the amino group is the common mode among the studied compounds and the results are in good agreement with the electrochemical measurements.

Ruthenium nanoparticles-modified reduced graphene prepared by a green method for high-performance supercapacitor application in neutral electrolyte

Here, we report a one-pot preparation method of a ruthenium-based reduced graphene oxide hybrid (Runano-based RGO). The synthesis is based on a single step for the reduction of Ru3+ (RuCl3) into Ru nanoparticles, and graphene oxide (GO) into reduced graphene oxide (RGO) without the use of any reducing agent. The structure of the hybrid material was ascertained using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and high resolution transmission spectroscopy (HRTEM). The change in pH of the synthesis media resulted in different structures and morphologies. A mixture of Ru and RuO2 (3:2) was obtained at pH 8.0, while only Ru-nanoparticles were obtained at pH 4.0. The supercapacitor performance of the hybrid was investigated in a neutral electrolyte, 1.0 M NaNO3, in a three-electrode setup. Runano-based RGO prepared at pH 8 exhibited a maximum specific capacitance of 270 F g−1 (238.5 mF cm−2), and maximum energy and power densities of 15 W h kg−1 and 76.4 kW kg−1, respectively. The proposed supercapacitor has a stable potential window up to 1.1 V with very good cycling stability over 5000 cycles at 24 A g−1.

Spectroscopic studies on styryl-, thienylethenyl- and furylethenyl-pyridines: molecular orbital treatment and effect of positional isomerism

The electronic absorption spectra of 2-, 3- and 4-styrylpyridines and 2- and 4-thienylethenyl and furylethenylpyridines in polar and non-polar solvents have been investigated. Different spectra were obtained for the different positional isomers. Solvent–solute interactions caused a shift in band maxima with solvent polarity that was dependent on the specific isomer under investigation. Spectral investigation indicated an extensive electronic interaction between the two heterocyclic rings joined through an ethylenic linkage.Molecular orbital calculations, using the INDO/S-CI procedure, were performed. The nature of the MO, whether localized or delocalized was a function of the specific isomer. The contribution of CT configuration to the electronic transition was different for different isomers. The solvent–solute interaction was calculated at the MO level. Satisfactory correspondence was found between calculated and experimental results.

Melatonin charge transfer complex with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone: Molecular structure, DFT studies, thermal analyses, evaluation of biological activity and utility for determination of melatonin in pure and dosage forms

A simple, accurate and fast spectrophotometric method for the quantitative determination of melatonin (ML) drug in its pure and pharmaceutical forms was developed based on the formation of its charge transfer complex with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an electron acceptor. The different conditions for this method were optimized accurately. The Lambert-Beers law was found to be valid over the concentration range of 4-100μgmL-1 ML. The solid form of the CT complex was structurally characterized by means of different spectral methods. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were carried out. The different quantum chemical parameters of the CT complex were calculated. Thermal properties of the CT complex and its kinetic thermodynamic parameters were studied, as well as its antimicrobial and antifungal activities were investigated. Molecular docking studies were performed to predict the binding modes of the CT complex components towards E. coli bacterial RNA and the receptor of breast cancer mutant oxidoreductase.

Investigation of the electronic spectra of furfuryl- and 2-thienyl-imino derivatives of some heterocycles: molecular orbital treatment

The electronic absorption spectra of furylmethylene and thienylmethylene derivatives of 2-aminopyridine, 2-aminopyrimidine and aminopyrazine have been investigated and INDO/S-CI molecular orbital calculations have been performed. The results predicted the position of n–π* transitions which were not observed experimentally. The coefficients of the CI wavefunction were used to predict the type of electronic transitions under consideration. It was confirmed that the anti conformer is the predominant one for the compounds studied.

Comparative MO investigation of hindered rotation and thermal decomposition of carbamates and thiocarbamates

Investigation of hindered rotation in carbamates reveals the high flexibility and ionic character of the CN bond as compared to common amides. This flexibility decreases in the case of thiocarbamates. The mechanism of activation of carbamates has been explored. Computations have proven the possibility of formation of an intramolecular H-bond in carbamates and thiocarbamates. This intramolecular H-bond is formed immediately after protonation of the carbamate. The possibility of formation of zwitterions as intermediates in the decomposition of carbamic and dithiocarbamic acids is discussed.

Indo-mo investigation of gas-phase acidities of carbamates and thiocarbamates

Gas-phase anion proton affinities of carbamic (I), thiol- (II), thio- (III) and dithiocarbamic (IV) acids are calculated by the INDO-MO method employing energy gradients for full geometry optimizations. The effect of d-type functions on sulphur on the calculated proton affinities has been examined. Detailed energy partitioning analysis enabled a much better understanding of the protonation process. Energetics of the isomerization II --> III have been computed and discussed.

Spectroscopic studies on some complexes of nickel(II) and palladium(II) with thiosemicarbazides

SummaryThe electronic absorption spectra of the complexes M(L)Cl2 and M(L)2Cl2 [M=NiII or PdII; L=thiosemicarbazide (tsc), 1-phenylthiosemicarbazide (1-phtsc), or 4-phenylthiosemicarbazide (4-phtsc)] were investigated in a number of solvents. The complexes Ni(tsc)Cl2, Ni(tsc)2Cl2, Ni(4-phtsc)Cl2 and Ni(4-phtsc)2Cl2 exist in a distorted Oh geometry when dissolved in any of the solvents used. On the other hand, the complex Ni(1-phtsc)2Cl2, although weakly paramagnetic, proved to be planar. Theoretical and experimental results proved that the complex has neither Oh nor Td geometry. Molecular orbital calculations were performed on some selected complex ions assuming a local point group symmetry of D2h.

Helical hydrophobic moment profiles in α and β tropomyosin

Abstract Averaged helical hydrophobic moment ratios have been evaluated in order to asses the potential of amphiphilic regions contributing to the helix-helix interaction responsible for stabilization of tropomyosin dimers. These ratios yield profiles that are higher in the amino-terminal half than in the carboxyl-terminal half of α and β tropomyosin chains. The higher profiles found in the amino-terminal half of α tropomyosin may contribute to the greater stability of the dimer in this region. Especially small helical hydrophobic moment ratios are found for fragments at each chain end and in the interior near Cys 190. These locations have previously been shown to be regions of instability in tropomyosin dimers