Investigations into the electrooxidation of guanosine-5′-triphosphate at the pyrolytic graphite electrode

The electrochemical oxidation of guanosine-5-triphosphate has been investigated in phosphate-containing electrolytes in the pH range 1.5–10.9 at a pyrolytic graphite electrode by cyclic sweep voltammetry, spectral studies, bulk electrolysis and related techniques. In this pH range, the oxidation occurred in a single well-defined peak (I_a). The peak potential of oxidation peaks (E_p) was found to be dependent on pH, concentration and sweep rate. The kinetics of the UV-absorbing intermediates was followed spectrophotometrically and the decay of the intermediate occurred in a pseudo-first-order reaction. The first-order rate constants for the disappearance of the UV-absorbing intermediate have also been calculated. The products of the electrode reaction were characterized by HPLC and GC/MS. A tentative mechanism for the formation of the products has also been suggested.     

Coherent dynamics of photoexcited green fluorescent proteins

The coherent dynamics of vibronic wave packets in the green fluorescent protein is reported. At room temperature the nonstationary dynamics following impulsive photoexcitation displays an oscillating optical transmissivity pattern with components at 67 fs (497 cm(-1)) and 59 fs (593 cm(-1)). Our results are complemented by ab initio calculations of the vibrational spectrum of the chromophore. This analysis shows the interplay between the dynamics of the aminoacidic structure and the electronic excitation in the primary optical events of green fluorescent proteins.     

FTICR/MS studies of gas-phase actinide ion reactions: fundamental chemical and physical properties of atomic and molecular actinide ions and neutrals

Fundamental aspects of the chemical and physical properties of atomic and molecular actinide ions and neutrals are being examined by Fourier transform ion cyclotron resonance mass spectrometry (FTICR/MS). To date, gas-phase reactivity studies of bare and ligated An⁺ and An²⁺ ions, where An = Th, Pa, U, Np, Pu, Am, and Cm, with oxidants and with hydrocarbons have been performed. Among the information that has been deduced from these studies are thermodynamic properties of neutral and ionic actinide oxide molecules and the role of the 5f electrons in actinide chemistry. Parallel theoretical studies of selected actinide molecular ions have also been carried out to substantiate the interpretation of the experimental observations.     

Stiff magnetofluid cosmological model

We intestigate the behavior of the magnetic field in a cosmological model filled with a stiff perfect fluid in general relativity. The magnetic field is due to an electric current along thex axis. The behavior of the model when a magnetic field is absent is also discussed.     

Enzymatic synthesis of multi-component copolymers and their structural characterization

The use of enzymes in synthetic applications has increased dramatically in the recent years and the field of polymer science is part of this trend. Synthesis of a variety of polymers using lipase catalyzed (Candida antarctica) polymerization reactions has led to a variety of new materials with interesting properties in our laboratories. This paper describes the synthesis of multi-component polyesters and mixed polymers having polyester and polyamide linkages under solvent-less conditions using Candida antarctica lipase B. The effect of a third component, i.e. a series of 1,omega-alkanediols (1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol and 1,16-hexadecanediol) on the copolymerization reaction of dimethyl 5-hydroxyisophthalate with poly(ethylene glycol 600) has been studied and the mechanism for the incorporation of the third component is proposed. We have also studied the effect of different functional groups during terpolymerization reaction of dimethyl 5-hydroxyisophthalate with poly(ethylene glycol) by adding a third component having different functionalities (1,6-hexanediol, 1,6-hexanediamine or 1,6-hexanedithiol) and compared the effect of hydroxyl, amine and thiol groups on the polymerization reactions.     

TG/DTA evidence of fluorine incorporation into YBa2Cu3O6⋅+δ

TG/DAT evidence to support incorporation of fluorine into superconducting orthorhombic lattice in YBa₂Cu₃O_6⋅+δ is presented. It is inferred that the F atom goes substitutionally in place of O atom in the lattice. Replacement of two oxygen atoms by four fluorine atoms did not alter theT _cof the product. By a similar replacement of two of its oxygens by fluorine atoms, the tetragonal modification of the oxide yields a product that remains non-superconducting down to 30 K.     

Polarography of some 3-arylazo-3-bromopentane-2,4-diones

The polarographic reduction of 3-arylazo-3-bromopentane-2,4-diones has been studied at different concentrations and pH. These compounds give a single 2-electron transfer and well-defined diffusion-controlled irreversible waves. The effect of fourteen substituents (electron-donating and electron-withdrawing) has been determined. A correlation between half-wave potential and Hammett substituent-constant has been established.     

Magnetic behavior of small amorphous particles produced by spark erosion

A model which admits a distribution in the Curie temperature values is proposed to explain an apparently conflicting low- and high-field magnetization behavior, in the critical transition region, in small amorphous particles produced by spark erosion.