Highly Efficient β-Functionalized Oxidomolybdenum(V) Corroles for Catalytic Oxidative Bromination of Phenols at Room Temperature

Two new β-functionalized oxidomolybdenum(V) corroles, oxido[3-formyl-5,10,15-triphenylcorrolato]molybdenum(V) ( Mo-1 ) and oxido[3-dicyanovinyl-5,10,15-triphenylcorrolato]molybdenum(V) ( Mo-2 ) were synthesized and characterized by various spectroscopic techniques and electrochemical studies. Mo-2 manifests splitted B bands due to x and y polarizations and highly red shifted longest B and Q bands due to the electron-deficient nature of the dicyanovinyl group. EPR data showed that these complexes exhibit an axial compression with d_xy¹ configuration. DFT studies revealed that HOMO and LUMO orbitals are stabilized in Mo-2 relative to Mo-1 . Mo-1 exhibits two successive reversible reductions and two oxidation potentials in cyclic voltammetry. Surprisingly, Mo-2 exhibits three successive reversible reductions and two oxidations; the one extra reduction could possibly be due to the reduction of the dicyanovinyl moiety. The catalytic activities of Mo-1 and Mo-2 for the oxidative bromination of various phenols using H₂O₂-KBr-HClO₄ mixture in water have been explored and exhibited excellent activity at a very low catalyst loading of 0.0030 and 0.0028 mol%, respectively. Both synthesized β-functionalized Mo(V) corroles manifest much higher conversion and TOF (59801–71174 h⁻¹) for oxidative bromination of phenols relative to earlier reported meso-functionalized Mo(V) corroles (20781–61646 h⁻¹). Hence, Mo-1 and Mo-2 mimic vanadium bromoperoxidase (VBPO) and act as functional models for these catalytic applications. These catalysts were reused upto 3 cycles and showed conversion rate upto 82 % indicating their excellent thermal and chemical stabilities.     

Genomically linked cellular protein databases derived from two-dimensional polyacrylamide gel electrophoresis

In its most useful form a cellular protein database should be genomically based, because it is the genome which determines both the total number of proteins a cell can make and the particular ones that will be made under any given condition. Such a database should trace each protein back to its structural gene, and should account for every structural gene of a cell. Recent advances in molecular biology greatly facilitate the construction of such gene-protein databases. The mapping of genes of unidentified proteins resolved from total cell extracts on two-dimensional gels can now be accomplished by largely biochemical methods, without the necessity of isolating mutants or performing genetic crosses. Other techniques permit one to search gels for the product of any newly discovered gene (or open reading frame) suspected of encoding a protein. Consequently, gene-protein indices can be built independently and simultaneously from either direction--deducing the genetic map from the protein pattern, or finding the protein pattern from information encoded in the genome. A database of this sort is being constructed for the bacterium, Escherichia coli. Given the current pace of DNA nucleotide sequencing, the development of total gene-protein indices for a variety of cells can be anticipated in the near future.     

Growth,spectral and thermal properties of KAP single crystals in the presence of DL‐Alanine and L‐Methionine amino acid dopants

Single crystals of potassium acid phthalate (KAP) and amino acid (DL‐Alanine, L‐Methionine) doped KAP were grown from aqueous solutions by slow cooling method. The grown crystals were characterized using powder X Ray diffraction (XRD) and Fourier Transform Infrared (FTIR) analysis. The thermal stability of KAP in the presence of dopants was analysed using Thermogravimetric and Differential Scanning caloriemetric (TGA/ DSC) studies and the maximum temperature for non linear optical application of this compound in the presence of dopants was found out. The transmittance of KAP was found to increase in the presence of dopants. Etch pits were observed for all the crystals using different etchants. Vickers microhardness tests were performed to study the mechanical stability of the crystals. The hardness of DL‐alanine doped KAP is more than that of L‐alanine doped KAP crystal. The dielectric constant and loss were determined as a function of temperature. Frequency response of the dielectric constant and dielectric loss factor have been studied over the frequency range of 50Hz – 5MHz. Second harmonic generation (SHG) was confirmed in all the crystals using the Kurtz and Perry powder technique. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Empirical model for electron impact ionization cross sections of neutral atoms

A simple empirical formula is proposed for the rapid calculation of electron impact total ionization cross sections both for the open- and closed-shell neutral atoms considered in the range 1≤ Z≤92 and the incident electron energies from threshold to about 10⁴ eV. The results of the present analysis are compared with the available experimental and theoretical data. The proposed model provides a fast method for calculating fairly accurate electron impact total ionization cross sections of atoms. This model may be a prudent choice, for the practitioners in the field of applied sciences e.g. in plasma modeling, due to its simple inherent structure.     

A simple scanning semiconductor diode laser source and its application in wavelength modulation spectroscopy around 825 nm

A very simple and inexpensive tunable semiconductor diode laser controller is designed for stable operation of the diode laser. The diode laser controller is stable within +/−8 μA and +/−10 mK, respectively. The noise spectrum of the current controller is studied by FFT analysis. We have used our home-made diode laser system in a tunable diode laser absorption spectrometer (TDLAS) to probe weak overtone transitions of water vapour molecule. The diode laser wavelength is coarsely tuned by changing the operating temperature to probe (2, 1, 1)←(0, 0, 0) band overtone transitions of water vapour within 818–835 nm. To demonstrate line shape study, seven transitions are scanned by ramping the drive current of the diode laser (at constant operating temperature) under different perturber (laboratory air) pressures within the sample cell. A balanced detector and a lock-in amplifier are used for phase sensitive detection purpose. Small current modulation amplitude, balanced detection and proper adjustment of the lock-in amplifier help to obtain a S/N ratio ranging from 100 to 7 using a small sample path length of 1.5 m. Experimentally obtained derivative spectrum is numerically integrated to reveal the original line shape and fitted with a nonlinear least squares fitting program to extract air broadening coefficients and line strength parameters. The spectroscopic line parameters are compared with the results from HITRAN database.     

Concise synthesis of chiral pyrazolo[4,3-f] [1,4]oxazepines and pyrazolo[4,3-f] [1,4]thiazepines bearing pyrazole unit

An efficient synthesis of pyrazolo [1,4]-oxazepines and [1,4]-thiazepines bearing a variety of alkyl and aryl groups with a chiral center has been developed. The synthesis started with readily available 5-chloro-pyrazole-4-carbaldehyde and chiral amino alcohols. The key step involves intramolecular imine formation. These classes of compounds are potentially useful as templates for drug discovery.     

SAMPL7 blind challenge: quantum–mechanical prediction of partition coefficients and acid dissociation constants for small drug-like molecules

The physicochemical properties of a drug molecule determine the therapeutic effectiveness of the drug. Thus, the development of fast and accurate theoretical approaches for the prediction of such properties is inevitable. The participation to the SAMPL7 challenge is based on the estimation of logP coefficients and pK_a values of small drug-like sulfonamide derivatives. Thereby, quantum mechanical calculations were carried out in order to calculate the free energy of solvation and the transfer energy of 22 drug-like compounds in different environments (water and n-octanol) by employing the SMD solvation model. For logP calculations, we studied eleven different methodologies to calculate the transfer free energies, the lowest RMSE value was obtained for the M06L/def2-TZVP//M06L/def2-SVP level of theory. On the other hand, we employed an isodesmic reaction scheme within the macro pK_a framework; this was based on selecting reference molecules similar to the SAMPL7 challenge molecules. Consequently, highly well correlated pK_a values were obtained with the M062X/6–311+G(2df,2p)//M052X/6–31+G(d,p) level of theory.

     

pH-induced structural transitions of caseins

Caseins are relatively small (molecular mass approximately 20 kDa), unstructured milk proteins of which the main components are referred to as alpha(s)-, beta- and kappa-casein. All three components lack a compact folded conformation, which can be ascribed to a combination of their low overall hydrophobicity and high net charge. Structural transitions of the three caseins in response to variation of pH were investigated using fluorescence and circular dichroism (CD) spectroscopy. Tryptophan emission parameters (intensity and wavelength of emission maximum) and CD spectra showed that at neutral and alkaline pH the caseins exist predominantly in random coil conformation. As the solvent is made acidic the added protons compensate the negative charges on the caseins and reduce the repulsion between like charged residues, allowing the casein chains to fold. At the pI (pH 4-5), the net charge on the protein tends to zero and the protein should approach its maximally structured state. Below pI, the uncompensated charges and their interactions reappear, resulting in slackening of the compact structure and formation of a partially unfolded intermediate. These conclusions were borne out by the biphasic pH-dependence of the fluorescence emission parameters of Trp as well as of ANS incubated with the caseins. Measurement of the efficiency of energy transfer between Trp (donor) and ANS (acceptor) and of the CD spectra of caseins as functions of pH were also consistent with this scenario.     

Comparative effects of different triazole compounds on growth, photosynthetic pigments and carbohydrate metabolism of Solenostemon rotundifolius

The effects of two triazole compounds, triadimefon and hexaconazole, on the growth and carbohydrate metabolism were studied in Solenostemon rotundifolius Poir., Morton plants under pot culture. Plants were treated with triadimefon at 15mg l(-1) and hexaconazole at 10mg l(-1) separately by soil drenching on 80, 110 and 140 days after planting (DAP). The plants were harvested randomly and growth parameters were studied on 90, 120 and 150 DAP for determining the effect of both the triazole on growth and chlorophyll pigments. These triazole compounds increased the chlorophyll pigments. However, both the treatments decreased the fresh and dry weights of shoot and leaf area. Both these triazole resulted in a marginal increase in starch content and decreased the sugar contents. The carbohydrate metabolizing enzymes alpha- and beta-amylase activities were reduced and invertase activity increased in S. rotundifolius under triadimefon and hexaconazole treatments.     

Enantioselective total synthesis of 1-epi-pathylactone A

[structure: see text]. The first enantioselective total synthesis of 1-epi-pathylactone A, 3, has been accomplished using a PhI(OAc)2-mediated domino reaction as a key step. No diastereomeric separation was required throughout the whole synthetic scheme presented in this paper. Comparison of 1H and 13C NMR spectral data of the synthetic product with the reported spectral data of natural pathylactone A, coupled with an X-ray crystallographic analysis, led to the conclusion that the C1 configuration in the original paper was erroneously ascribed to (R).