Vector and axial-vector mesons at finite temperature

We consider the thermal correlation functions of vector and axial-vector currents and evaluate corrections to the vector and axial-vector meson pole terms to one loop in chiral perturbation theory. As expected, the pole positions do not shift to leading order in temperature. But the residues decrease with temperature. We review briefly other methods in the literature to determine these pole parameters. We find our evaluation to disprove a result on the mixing of the correlation functions at finite temperature. Received: 30 May 2002 / Published online: 30 August 2002     

Masses of light quarks in quantum chromodynamics

We try to determine light quark masses by considering sum rules for the vacuum expectation value of the time-ordered correlation function of two divergences of the axial vector current. The evaluation is carried out at momenta high enough for the non-perturbative contributions to be negligible. We find that the average mass of the up and down quark at a momentum of 1 GeV lies between 3.3 and 7.9 MeV while that for the strange quark lies between 84 and 212 MeV. The ranges of values reflect predominantly the uncertainty in the absorptive part in the low energy region (?1.7 GeV).     

Study of theS-matrix near bound states in the continuum

The behaviour ofS-matrix for potentials generating bound states in continuum in the neighbourhood of the positive bound state energies is studied. It is shown that unlike the case of usual negative energy bound states, theS-matrix does not have a pole at the positive bound state energy but becomes unity at the energy corresponding to bound states in continuum. Calculations ofS-waveS-matrix for a local potential constructed by Stillinger and Herrick and a separable nonlocal potential constructed by the present authors verify these results. Our results indicate that the bound states embedded in continuum constructedvia the von Neumann and Wigner procedure cannot be interpreted as resonances with zero width.     

Studies on nucleophilic ring opening of some epoxides in polar protic solvents—I

The epoxides of the type 4 undergo ring-opening with carbanions; without exception, the nucleophiles attack at C-1 in spite of the increased steric hindrance at the site (as in epoxides 4b and 4e having peri-substituents). Interaction of the epoxide 4b with the anion of diethyl methylmalonate in refluxing t-butanol afforded, besides other products, the novel cyclopropane carboxylic acid 12. What is more significant is that although the formation of the trans-lactone on the whole is favoured in the ring opening of epoxides 4, at least in two cases, 4b and 4c, there is considerable formation of cis-lactones, a result that remains unexplained. Attempted synthesis of the model cis-lactone 3c always resulted in the formation of a 1:1 mixture of the cis-3c and the trans-lactone 2a. The stereochemistries of the cis- and the trans-lactones described in this paper have been unambiguously established from the position of the 3a-proton signals of these γ-lactones in their NMR spectra.     

An investigation on the analytical potential of polymerized liposomes bound to lanthanide ions for protein analysis

We present a promising approach to protein sensing based on Eu3+ ions incorporated into polymerized liposomes. The sensitization of Eu3+ is accomplished with 5-aminosalicylic acid, which provides energy transfer for a stable reference signal and a wide wavelength excitation range free from protein interference. The lipophilic character of polymerized liposomes provides the appropriate platform for protein interaction with the lanthanide ion. Quantitative analysis is based on the linear relationship between the luminescence signal of Eu3+ and protein concentration. Because no spectral shift of the lanthanide luminescence is observed upon protein interaction, qualitative analysis is based on the luminescence lifetime of polymerized liposomes. This parameter, which changes significantly upon protein-liposome interaction, follows a well-behaved single-exponential decay that might be useful for protein identification.     

Thermodynamic studies on the recognition of flexible peptides by transition-metal complexes

Strong and selective binding to a trihistidine peptide has been achieved employing Cu(2+)-histidine interactions in aqueous medium (25 mM HEPES buffer, pH 7.0). When the pattern of cupric ions on a complex matched with the pattern of histidines on the peptide, a strong and selective binding was observed. UV-vis spectroscopic studies show that the cupric ions coordinate to the histidines of the peptides. Thermodynamic studies reveal that the binding process is enthalpy driven over the entire range of working temperature (25-40 degrees C). An enthalpy-entropy compensation effect was also observed.     

Parametrically Excited Non-Linear Traveling Beams with and without External Forcing

The effects of parametric excitation on a traveling beam, both with and without an external harmonic excitation, have been studied including the non-linear terms. Non-linear, complex normal modes have been used for the response analysis. Detailed numerical results are presented to show the effects of non-linearity on the stability of the parametrically excited system. In the presence of both parametric and external harmonic excitations, the response characteristics are found to be similar to that of a Duffing oscillator. The results are sensitive to the relative strengths of and the phase difference between the two forms of excitations.     

Evaluation of carbonic anhydrase and paraoxonase inhibition activities and molecular docking studies of highly water-soluble sulfonated phthalocyanines

The investigation of carbonic anhydrase and paraoxonase enzyme inhibition properties of water-soluble zinc and gallium phthalocyanine complexes ( 1 and 2 ) are reported for the first time. The binding of p-sulfonylphenoxy moieties to the phthalocyanine structure favors excellent solubilities in water, as well as providing an inhibition effect on carbonic anhydrase (CA) I and II isoenzymes and paraoxonase (PON1) enzyme. According to biological activity results, both complexes inhibited hCA I, hCA II, and PON1. Whereas 1 and 2 showed moderate hCA I and hCA II (off-target cytosolic isoforms) inhibitory activity (Ki values of 26.09 µM and 43.11 µM for hCA I and 30.95 µM and 33.19 µM for hCA II, respectively), they exhibited strong PON1 (associated with high-density lipoprotein [HDL]) inhibitory activity (Ki values of 0.37 µM and 0.27 µM, respectively). The inhibition kinetics were analyzed by Lineweaver–Burk double reciprocal plots. It revealed that 1 and 2 were noncompetitive inhibitors against PON1, hCA I, and hCA II. These complexes can be more advantageous than other synthetic CA and PON inhibitors due to their water solubility. Docking studies were carried out to examine the interactions between hCA I, hCA II, and PON1 inhibitors and metal complexes at a molecular level and to predict binding energies.     

Highly improved electrocatalytic oxidation of dimethylamine borane on silver nanoparticles modified polymer composite electrode

Dimethylamine borane (DMAB) is a promising fuel alternative for fuel cell applications. In this work cyclic voltammetric behavior of DMAB was investigated on the polymerized aminophenol film decorated with Ag nanoparticles in alkaline media. The polymer film was formed on the glassy carbon electrode by electrochemical technique and then, the surface was modified with Ag nanoparticles. The surface of the modified electrode was identified by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy techniques. The developed electrode has displayed high electrocatalytic activity for DMAB oxidation in alkaline media depending on the supporting electrolyte concentration. Experimental parameters such as cycle number used in electropolymerization of p-aminophenol, deposition of Ag nanoparticles and supporting electrolyte were optimized.