Observation of inter-grain Josephson effects in Y-Ba-Cu-O samples

Josephson effects have been observed in bulk samples of Y-Ba-Cu-O. The magnitude of the zero-voltage current is found to change systematically with externally applied small magnetic fields of a few mG. It is also found to vary when samples are irradiated with microwaves. These observations suggest the presence of inter-grain Josephson junctions.     

Oxidimetric estimation of chloramphenicol with aromatic sulphonyl monohaloamines

The reaction between chloramphenicol and chloramine-T, chloramine-B, bromamine-B or bromamine-T has been found to proceed quantitatively over a wide range of experimental conditions. Simple titrimetric procedures for the estimation of chloramphenicol with N-haloamines have been developed. Oxidation of the antibiotic involves a four-electron change and the products of oxidation have been identified. The methods are useful for the estimation of this antibiotic in medicinal formulations.     

Polyaniline film formation in hexadecyl trimethyl ammonium bromide admicelles on hydrous zirconia surface

Formation of a thin polyaniline film on hydrous zirconia (ZrO2) surface was carried out using adsorbed surfactant bilayers on ZrO2 as reaction sites. Aniline was adsolubilized in hexadecyltrimethylammonium bromide (HDTAB) admicelles formed on the surface of ZrO2 by adsorption. Subsequent polymerization of the adsolubilized aniline monomer showed effective conversion of aniline to polyaniline. The formation of the polyaniline coated ZrO2 has been confirmed by UV-visible spectroscopy, FT-IR spectroscopy, and conductivity measurements. Various parameters involved during the adsorption process were studied. Selection of pH 9.0 as the pH of all experimental feed solutions was governed by the knowledge of point of zero charge (PZC) of ZrO2. Effect of aniline concentration on HDTAB adsorption was studied and it was observed that increase in aniline concentration decreased the amount of HDTAB adsorbed on ZrO2. Addition of salt (0.05 M NaCl) in the feed solution increased HDTAB adsorption and drastically reduced the effect of aniline concentration on HDTAB adsorption.     

Free-energy component analysis of 40 protein-DNA complexes: a consensus view on the thermodynamics of binding at the molecular level

Noncovalent association of proteins to specific target sites on DNA--a process central to gene expression and regulation--has thus far proven to be idiosyncratic and elusive to generalizations on the nature of the driving forces. The spate of structural information on protein--DNA complexes sets the stage for theoretical investigations on the molecular thermodynamics of binding aimed at identifying forces responsible for specific macromolecular recognition. Computation of absolute binding free energies for systems of this complexity transiting from structural information is a stupendous task. Adopting some recent progresses in treating atomic level interactions in proteins and nucleic acids including solvent and salt effects, we have put together an energy component methodology cast in a phenomenological mode and amenable to systematic improvements and developed a computational first atlas of the free energy contributors to binding in approximately 40 protein-DNA complexes representing a variety of structural motifs and functions. Illustrating vividly the compensatory nature of the free energy components contributing to the energetics of recognition for attaining optimal binding, our results highlight unambiguously the roles played by packing, electrostatics including hydrogen bonds, ion and water release (cavitation) in protein-DNA binding. Cavitation and van der Waals contributions without exception favor complexation. The electrostatics is marginally unfavorable in a consensus view. Basic residues on the protein contribute favorably to binding despite the desolvation expense. The electrostatics arising from the acidic and neutral residues proves unfavorable to binding. An enveloping mode of binding to short stretches of DNA makes for a strong unfavorable net electrostatics but a highly favorable van der Waals and cavitation contribution. Thus, noncovalent protein-DNA association is a system-specific fine balancing act of these diverse competing forces. With the advances in computational methods as applied to macromolecular recognition, the challenge now seems to be to correlate the differential (initial vs. final) energetics to substituent effects in drug design and to move from affinity to specificity.     

Monte Carlo study of the aqueous hydration of dimethylphosphate conformations

Monte Carlo computer simulations were performed on dilute aqueous solutions of the dimethylphosphate anion and the sodium dimethylphosphate ion pair, with the two phosphodiester torsional angles in the gauche–gauche, gauche–trans, and trans–trans conformations. The structural and energetic aspects of the aqueous hydration of each molecule were analyzed in terms of quasi component distribution functions based on the proximity criterion and partitioned into ionic, hydrophilic, and hydrophobic contributions to facilitate an understanding of the hydration pattern and conformational trends in these multifunctional solutes. Special attention was also paid to methodological issues affecting hydration, such as statistical uncertainty in the determined hydration indices, choice of partial atomic charges for the solute atoms, and solute–water interaction potentials adopted in the simulations. The results showed that gauche–trans and gauche–gauche forms are equally favorable for the dimethylphosphate anion with the trans extended form destabilized by hydration. The sodium dimethylphosphate ion pair hydration energetically favors the trans–trans conformation.     

Development of Biosensor for Catechol Using Electrosynthesized Poly(3‐methylthiophene) and Incorporation of LAC Simultaneously

Simultaneous electropolymerization of 3‐methylthiophene and incorporation of Laccase (LAC) was carried out in the presence of propylene carbonate as a medium by amperometric method. This enzyme modified electrode was used for the sensing of polyphenol. Catechol is taken as a model compound for the study. UV‐Vis spectral studies suggest no denaturation of LAC in presence of propylene carbonate. The SEM studies reveal the surface morphology and incorporation of LAC in P3MT with agglomerated flaky masses are observed in with and without enzyme micrographs. The cyclic voltammograms were recorded for 0.01 mM catechol on plain glassy carbon, polymer and enzyme incorporated electrodes at pH 6.0 and scan rate 50 mV s^?1. The fabricated electrochemical biosensor was used for the determination of catechol in aqueous solution by Differential Pulse Voltammetry (DPV) technique. The concentration linear range of 8×10^?8 to 1.4×10^?5 M a value of Michealis? Menten constant K_m=7.67 µmol dm^?3 and activation energy is 32.75 kJ mol^?1. It retains 83 % of the original activity after 60 days which is much higher than that of other biosensors. The developed biosensor was used to quantify catechol in the determination in real samples.     

Shock Processing of Amino Acids Leading to Complex Structures—Implications to the Origin of Life

The building blocks of life, amino acids, are believed to have been synthesized in the extreme conditions that prevail in space, starting from simple molecules containing hydrogen, carbon, oxygen and nitrogen. However, the fate and role of amino acids when they are subjected to similar processes largely remain unexplored. Here we report, for the first time, that shock processed amino acids tend to form complex agglomerate structures. Such structures are formed on timescales of about 2 ms due to impact induced shock heating and subsequent cooling. This discovery suggests that the building blocks of life could have self-assembled not just on Earth but on other planetary bodies as a result of impact events. Our study also provides further experimental evidence for the ‘threads’ observed in meteorites being due to assemblages of (bio)molecules arising from impact-induced shocks.     

Ruthenium(III) complexes of amine-bis(phenolate) ligands as catalysts for transfer hydrogenation of ketones

Twelve ruthenium(III) complexes bearing amine-bis(phenolate) tripodal ligands of general formula [Ru(L¹–L³)(X)(EPh₃)₂] (where L¹–L³ are dianionic tridentate chelator) have been synthesized by the reaction of ruthenium(III) precursors [RuX₃(EPh₃)₃] (where E = P, X = Cl; E = As, X = Cl or Br) and [RuBr₃(PPh₃)₂(CH₃OH)] with the tripodal tridentate ligands H₂L¹, H₂L² and H₂L³ in benzene in 1:1 molar ratio. The newly synthesized complexes have been characterized by analytical (elemental and magnetic susceptibility) and spectral methods. The complexes are one electron paramagnetic (low-spin, d⁵) in nature. The EPR spectra of the powdered samples at RT and the liquid samples at LNT shows the presence of three different ‘g’ values (g_x ≠ g_y ≠ g_z) indicate a rhombic distortion around the ruthenium ion. The redox potentials indicate that all the complexes undergo one electron transfer process. The catalytic activity of one of the complexes [Ru(pcr-chx)Br(AsPh₃)₂] was examined in the transfer hydrogenation of ketones and was found to be efficient with conversion up to 99% in the presence of isopropanol/KOH.