Spectroscopic and docking studies of the binding of two stereoisomeric antioxidant catechins to serum albumins

The interactions of two stereoisomeric antioxidant flavonoids, catechin (C) and epicatechin (EC) with bovine serum albumin (BSA) and human serum albumin (HSA), have been investigated by steady state and time resolved fluorescence, phosphorescence, circular dichroism (CD), FTIR and protein–ligand docking studies. The steady-state fluorescence studies indicate a single binding site for both the ligands. FTIR spectra suggest that in both the albumins, C and EC stabilize the α-helix at the cost of a corresponding loss in the β-sheet structure. CD studies have been carried out using (±)C, and both the epimers (+)C and (?)C. The low temperature phosphorescence and protein–ligand [(+), (?) and (±) forms of C and EC] docking studies indicate that the ligands bind in the proximity of Trp 134 of BSA and Trp 214 of HSA, thereby changing their solvent accessible surface areas (ASA). Asn 158 and Glu 130 side chains are found to be within the hydrogen bonding distance from the phenolic –OH groups of C and EC in the case of BSA complex. C and EC are located within the binding pocket of sub-domain IIa of HSA.     

The real-time gamma radiation dosimetry with TeO2 thin films

A detailed study of the effect of gamma radiation on the current–voltage characteristics of the TeO₂ thin films of different thicknesses, prepared by thermal evaporation in a vacuum, has been carried out for a much wider range of the gamma radiation doses than made here-to-fore. Subsequently, for the thin films of different thicknesses at different applied voltages, the variations of the current density with dose have been obtained. The current density increases near linearly with the gamma radiation dose up to a critical radiation dose, a dose value higher for the thicker films and decreases thereafter. The sensitivities of these TeO₂ thin films at different applied voltages have been found to be in the range 1.2–37.0 nA/cm²/μGy. Correspondingly, the detection limits have also been estimated and have been found to be in the range 0.22–2.16 mGy. Clearly, the TeO₂ thin films have high potential for their use as real-time gamma radiation dosimeters in monitoring the gamma radiation doses under a variety of practical situations involving low level to high level of the doses.     

Structural, magnetic and electric properties of HoMnO3 films on SrTiO3(001)

HoMnO₃ films were grown on pure and Nb-doped SrTiO₃ (001) substrates by pulsed laser deposition. The films grew epitaxially with the c-axis along the substrate normal. Varying the deposition temperature between 650 and 850 °C did not significantly affect the structural and magnetic properties of the films, whereas growth in oxygen partial pressures below 0.01 mbar lead to a degradation of the structural properties. Some of the films had a ferromagnetic-like magnetic phase transition at about 45 K, probably related to Mn₃O₄ precipitates; this magnetic response was isotropic. The Ho sublattice was found to be paramagnetic down to 5 K, but showing a pronounced anisotropy with the c-axis being the hard axis. The films showed a distinct dielectric anomaly at 16 K that depended on voltage and slightly on frequency in the range between 1 kHz and 1 MHz. The magnetoelectric effect was large with an in-plane field of 8 T suppressing the dielectric anomaly completely.     

Two-potential theory of electric and magnetic charges via duality transformation

Dirac, Schwinger and Zwanziger theories of electric and magnetic charges are obtained via duality transformation. Analogous construction for three Euclidean dimensions, with magnetic charges interacting with electric currents, is also done. The role of Dirac strings as dislocations in the configurations of gauge potential is emphasized.     

Optimal production inventory policy for defective items with fuzzy time period

In this paper, an optimal production inventory model with fuzzy time period and fuzzy inventory costs for defective items is formulated and solved under fuzzy space constraint. Here, the rate of production is assumed to be a function of time and considered as a control variable. Also the demand is linearly stock dependent. The defective rate is taken as random, the inventory holding cost and production cost are imprecise. The fuzzy parameters are converted to crisp ones using credibility measure theory. The different items have the different imprecise time periods and the minimization of cost for each item leads to a multi-objective optimization problem. The model is under the single management house and desired inventory level and product cost for each item are prescribed. The multi-objective problem is reduced to a single objective problem using Global Criteria Method (GCM) and solved with the help of Fuzzy Riemann Integral (FRI) method, Kuhn–Tucker condition and Generalised Reduced Gradient (GRG) technique. In optimum results including production functions and corresponding optimum costs for the different models are obtained and then are presented in tabular forms.     

Stereocontrolled synthesis of dihydropseudoclovene-B

Aryl participated intramolecular cyclisation of the bromophenol 16 yielded the dienone 17 which was converted into dihydropseudoclovene-B (7) via a stereocontrolled route.     

Ceramic-based nanoparticles entrapping water-insoluble photosensitizing anticancer drugs: a novel drug-carrier system for photodynamic therapy

A novel nanoparticle-based drug carrier for photodynamic therapy is reported which can provide stable aqueous dispersion of hydrophobic photosensitizers, yet preserve the key step of photogeneration of singlet oxygen, necessary for photodynamic action. A multidisciplinary approach is utilized which involves (i) nanochemistry in micellar cavity to produce these carriers, (ii) spectroscopy to confirm singlet oxygen production, and (iii) in vitro studies using tumor cells to investigate drug-carrier uptake and destruction of cancer cells by photodynamic action. Ultrafine organically modified silica-based nanoparticles (diameter approximately 30 nm), entrapping water-insoluble photosensitizing anticancer drug 2-devinyl-2-(1-hexyloxyethyl) pyropheophorbide, have been synthesized in the nonpolar core of micelles by hydrolysis of triethoxyvinylsilane. The resulting drug-doped nanoparticles are spherical, highly monodispersed, and stable in aqueous system. The entrapped drug is more fluorescent in aqueous medium than the free drug, permitting use of fluorescence bioimaging studies. Irradiation of the photosensitizing drug entrapped in nanoparticles with light of suitable wavelength results in efficient generation of singlet oxygen, which is made possible by the inherent porosity of the nanoparticles. In vitro studies have demonstrated the active uptake of drug-doped nanoparticles into the cytosol of tumor cells. Significant damage to such impregnated tumor cells was observed upon irradiation with light of wavelength 650 nm. Thus, the potential of using ceramic-based nanoparticles as drug carriers for photodynamic therapy has been demonstrated.     

Dimeric cyclopalladated azobenzenes: structural differences between 2-hydroxypyridine and 2-mercaptopyridine bridged complexes

Binuclear chloro-bridged cyclopalladated azobenzenes [Pd(A)Cl]₂ (A=ortho-metallated azobenzene or its derivatives) have been reacted with aqueous (aq.) AgNO₃ followed by the addition of 2-hydroxypyridine (2-PyOH; donor centres of deprotonated form abbreviated N,O)/2-mercaptopyridine (2-PySH; donor centres of deprotonated form abbreviated N,S) in presence of Et₃N to synthesise bridged dinuclear compound [Pd(A)(μ-N,O)]₂–[Pd(A)(μ-N,S)]₂. The compositions of the complexes have been established by elemental analyses, IR, UV–vis, ¹H and ¹³C-NMR spectral data. The structural confirmation has been carried out by X-ray crystallography. The structures show anti-symmetric metallacycle in the dimer and N,O/N,S bridging arrangement. The dimer [Pd(A₁)(μ-N,X)]₂ shows strong PdPd interaction (A₁=2-(phenylazo)benzene). The coordination mode in [Pd(A₁)(μ-N,O)]₂ shows trans pyridine-N to Pd---N(azo) bond while in [Pd(A₁)(μ-N,S)]₂ pyridine-N is trans to the Pd---C bond. The square planes are convergent towards heterocyclic bridging side.     

Investigations of the solvent polarity effect on the photophysical properties of coumarin-7 dye

Photophysical investigations of coumarin-7 (C7) dye in different solvents using absorption, steady-state fluorescence and time-resolved fluorescence measurements reveal the behavioral changes of the dye in nonpolar and other solvents. In moderate to higher polarity solvents, the experimental parameters such as fluorescence quantum yield (Phif), fluorescence lifetime (tauf), radiative rate constant (k(f)), nonradiative rate constant (k(nr)) and Stokes' shift (Deltav) follow almost linear correlations with the Lippert-Mataga solvent polarity parameter Deltaf but show unusual deviations in nonpolar solvents. From the observed results, it is inferred that the dye exists in a planar intramolecular charge transfer structure in moderate to higher polarity solvents, but in nonpolar solvents, the dye exists in a nonplanar structure with its 7-NEt2 group adopting a pyramidal type of configuration. Unlike some of the other coumarin dyes, namely coumarin-120 (C120) (4-CH3-7-NH2-1,2-benzopyrone) and coumarin-151 (C151) 4-CF3-7-NH2-1,2-benzopyrone), which also show similar structural changes in nonpolar and other solvents, the C7 dye does not show any activation-controlled deexcitation process in nonpolar solvents. This is attributed to the very slow flip-flop motion of the 7-NEt2 group of the C7 dye in comparison with the very fast flip-flop motion of the 7-NH2 group in the C120 and C151 dyes. Qualitative potential energy diagrams are presented to rationalize the observed results of C7 dye and to compare these with those of the other dyes such as C120 and C151. A support for the observed results and interpretation has also been obtained from quantum chemical calculations on the structures of the C7 dye.