Journal of Physical and Theoretical Chemistry
Volume:4 Issue: 3, Autumn 2007

DPPC (dipalmitoylphosphatidylcholine) and DMPC (dimyristoylphosphatidylcholine) are taken asphospholipids with an equal polar heads and with the difference in the length of hydrocarbonchains. Results obtain from the structural optimization of the isolated DPPC and DMPC in the gasphase, at the Hartree-Fock level of theory by means of STO-3g,3-21G, 6-31G and 6-31G* basissets. the most important dihedral angle of these molecules (DPPC and DMPC) is chosen and theenergy of 14 important atoms were scanned within 180 degrees rotation and sites that have mostchanges are determined and any rotated molecule separately placed in the 19 solvents (The methodis HF/6-31G* model) and then dielectric effect of surrounding were analyzed. The solvent effecton the stability of DPPC & DMPC molecules were discussed using Onsager model.

Sol-gel and polymeric membrane electrodes, based on thiacalix[4]arene as a neutral carrier, weresuccessfully developed for the detection of VO2+ in aqueous solutions. The sol-gel and PVCmembrane electrodes exhibited linear response with Nernstian slopes of 29.3 and 28.4 mV perdecade, respectively, within the vanadyl ion concentration ranges from 1.0 × 10-6 to 1.0 × 10-1mol dm-3 and from 1.0 × 10-5 to 1.0 × 10-1 mol dm-3 for sol-gel and PVC membrane sensors.The PVC-based and sol-gel electrodes show detection limits of 3.1 × 10-6 and 4.9 × 10-7 mol dm-3, respectively, and also response time of about 15 s to achieve a 95% steady potential for VO2+concentration. By testing the stability lifetimes of the electrodes over a six-month period, nosignificant change was observed in the performance of the sol-gel electrode, however, the PVCbasedvanadyl-selective electrode exhibited a gradual decrease in the slope after two months.Investigating the influence of membrane composition, the pH of the test solution, and theinterfering ions on the electrodes performance revealed good selectivity of electrodes for a numberof alkali, alkaline earth, transition and heavy metal ions. The determined isothermal temperaturecoefficients of these electrodes showed a better thermal stability of sol-gel electrode rather thanthat of the PVC-based vanadyl-selective electrode, however, the electrodes performance isdeteriorated by temperatures higher than 50 °C.

Using UV-vis spectrophotometic method, the formation constants for interaction of Cd2+(aq) andCo2+(aq) ions with L-Alanine were experimentally studied at pH = 4.1 ± 0.01 (50mM of potassiumhydrogen phthalate buffer), ionic strength of 0.1M potassium nitrate and at 5 differenttemperatures 15,20, 25,30 and 35°C. The optical absorption spectra of mixtures containingconsidered cations and L-Alanine were analyzed by using SQUAD software, in order to obtainthe formation constants and the stoichiometry of respect complexes. The best fitting of our resultsshowed that the 2:1 complex respect to each studied system (Cd2+(aq) + L-Alanine) and (Co2+(aq) +L-Alanine) is formed. Regarding the values of formation constants at different temperatures andusing Van't Hoff equation, enable us to calculate the respect thermodynamic functions offormation such as ΔH , ΔS , ΔG , … of studied complexes.

12-molybdophosphoric acid (PMo12) was encaged into HMOR zeolite by “ship in a bottle”method in aqueous phase which is strongly retained and not easily leached from the host channels.The solid was characterized by XRD prior to using it for the electrode preparation. This compoundwas incorporated with a carbon paste electrode for cyclic voltammetric measurements. PMo12immobilized on the support underwent a quasi-reversible electrochemical redox reaction. Invarious electrolyte solutions and also changing the pH range from 0 to 5, the ΔEp remainspractically constant, i.e. 179mV. The comparison of these voltammograms with those in aqueousphase shows remarkable similarities, therefore it is may concluded that this hybrid material hasredox catalytic properties and high surface area, simultaneously.

Paper recycling in an increasingly environmentally conscious world is gaining importance. Withrapid developments in deinking processes for the reuse of secondary fibers being made, therecycling process is become more and more efficient. This work investigated the effect ofchemical different treatments including H2O2 and NaOH on repulping and flotation operationsduring the deinking of laser printed copy paper, and freeness and physical properties of handsheetswere evaluated. In order to access to more desirable quality specification and strength properties inpaper production recovered from primary materials, NaOH and H2O2 , as an effective factor inrecovery, were added to the pulp of printer waste paper in a different ratio. Results of this researchshow that, the optimum rate of handsheet paper was in freeness 300-400 ml, which this rate, havebetter effect. In optical and mechanical properties of handsheet papers, maximum and minimumrate were 2 to 3 (C) and 1 to 2 (A) percent ratio of NaOH to H2O2 respectively.

Jute modified has been used for adsorption of Cr (VI), Cd (II) and Pb (II) ions over a range ofinitial metal ion concentration. Adsorption process is done in batch mode. Adsorption isotherms ofthe heavy metals on adsorbents prepared were determined and correlated with common isothermequations. It was found that the Freundlich isotherm is better than Langmuir for explaining thebehavior of adsorption. The effect of some parameters such as adsorbent quantity, pH value andtemperature were investigated. The enlargement of pH value until 5 and adsorbent quantityincrease the adsorption quantity. Whereas exceed of the temperature has the reverse effect.

Surface oxidized carbon vulcane XC-72 is prepared as catalyst support and platinumnanoparticles are chemically anchored onto the modified surface. The nanoparticles of Pt weresynthesized by reduction of H2PtCl6 with sodium borohydride in a 5.5 M buffer solution ofsodium citrate; the complexation of citrate with metal ions is beneficial to the formation ofnanoparticles. The electro-oxidation of liquid methanol of this catalyst as a thin layer on glassycarbon electrode is investigated at room temperature by cyclic voltammetery. The results showthat surface oxidized carbon vulcane support allows to obtain higher power density (about threetimes higher) in comparison to carbon vulcane XC-72 based electro catalyst.

A new metal-organic compound, [Fe(Pydc)(DMSO)(H2O)Cl], (where Pydc is pyridine-2, 6-dicarboxylate and DMSO is dimethyl sulfoxide), has been synthesized and characterized by singlecrystal X-ray diffraction, TGA/DTA, IR and Raman spectroscopy. Green-yellow crystals,crystallized in the monoclinic system, space group P21/n, a = 7.2461(4) Å, b = 10.3018(4) Å, c =17.7667(10) Å, α = 90°, β = 90.014°(5), 1329.54(12) Å3, Z = 4 and R = 0.0317. In the molecule ofthe crystallized compound Fe ion is sixfold coordinated with distorted octahedral geometry andthe structure is stabilized by O-H…O hydrogen bonds.

HF level of ab initio calculations with basis-set 6-31G including full counterpoise correction hasbeen applied to compute the AspHis potential with the Ser and HisSer potential with the Asp inAspHisSer trimer. The potential energy surface has a minimum of -16.765 kcal/mol in R1=1.912nm and R2=2.719 nm. The optimum computed curves for two interactions were fitted withintermolecular pair potential models, including of Lennard-Jones, Kihara, Buckingham Exp-6 andBuckingham Exp-6-8 potentials. The Buckingham exponential potentials gave the best fit. Thesepotentials have been used to calculate the second virial coefficient for AspHis-Ser and Asp-HisSerinteractions. As we expected B2 for Asp-HisSer interaction was more negative from AspHis-Serinteraction.

The interaction of bovine serum albumin ( BSA) and egg albumin with water solublephthalocyanine, cobalt (ΙΙ) 4, 4′ , 4′′, 4′′′- tetrasulfophthalocyanine ( CoTSPc) , has been studiedby the UV- Vis method at pH 7.0 and five different temperatures 20, 25, 30, 35 and 40°C. Theformation constants have been elucidated by using spectrophotometric titration and computerSQUAD program data refinement. The thermodynamic parameters ΔH°, ΔG°and ΔS° at 5 differenttemperatures were calculated. The results showed that the best fitting corresponds to a 1: 1complex model between BSA and egg albumin with CoTSPc. Formation constants decrease withincreasing temperature.The formation constants showed that bonding effect between egg albuminand CoTSPc is stronger than BSA.