Derepressed 2-deoxyglucose-resistant mutants of Aspergillus niger with altered hexokinase and acid phosphatase activity in hyperproduction of β-fructofuranosidase

Aspergillus niger NRRL330 produces extracellular β-fructofuranosidase (Ffase), and its production is subject to repression by hexoses in the medium. After ultraviolet mutagenization and selection, seven derepressed mutants resistant to 2-deoxyglucose (2-DG) were isolated on Czapek’s minimal medium containing glycerol. One of the mutants, designated DGRA-1, produced higher levels of Ffase. A considerable difference occurred in the mutants with reference to hexokinase and intracellular acid phosphatase activities. The hexokinase activity of the mutant DGRA-1 (0.69 U/mg) was 1.8-fold higher than the wild type (0.38U/mg). Intracellular acid phosphatase activity of the mutant DGRA-1 (0.83 U/g of mycelia) was twofold higher than that of the wild type (0.42U/g of mycelia), suggesting that phosphorylation and dephosphorylation steps could attribute to the 2-DG resistance of A. niger. However, additional mutations could account for the increased production of Ffase in the mutant DGRA-1.     

Hydrogenation of nitroaromatics to anilines catalyzed by air‐stable arene ruthenium (II)–NNN pincer complexes

A series of air‐stable, phosphine‐free arene ruthenium (II)–NNN pincer complexes (RuL, RuL¹, RuL² and RuL³) have been synthesized and characterized by spectroscopic and single‐crystal X‐ray analysis. Further, arene ruthenium (II)–NNN pincer complexes have been used as catalyst for hydrogenation of nitroaromatics into aniline in the presence of NaBH₄ at room temperature. The catalytic process suggested highly chemo‐selective nitroreduction with wide functional group tolerance.     

Synthesis,characterization, DNA binding,DNA cleavage,antioxidant and in vitro cytotoxicity studies of ruthenium(II) complexes containing hydrazone ligands

The synthesis, spectral characterization, and biological studies of ruthenium(II) hydrazone complexes [RuCl(CO)(PPh₃)₂L] (where L = hydrazone ligands) have been carried out. The hydrazones are monobasic bidentate ligands with O and N as the donors and are preferably found in the enol form in all the complexes. The molecular structure of the ligands HL¹, HL²_, and HL³ were determined by single-crystal X-ray diffraction. The DNA binding studies of the ligands and complexes were carried out by absorption spectroscopic and viscosity measurements. The results revealed that the ligands and complexes bind to DNA via intercalation. The DNA cleavage activity of the complexes, evaluated by gel electrophoresis assay, revealed that the complexes are good DNA cleaving agents. The antioxidant properties of the complexes were evaluated against DPPH, OH, and NO radicals, which showed that the complexes have strong radical-scavenging. Further, the in vitro cytotoxic effect of the complexes examined on HeLa and MCF-7 cancer cell lines showed that the complexes exhibited significant anticancer activity.     

Studies on growth,induction period,interfacial energy and metastable zonewidth of m‐nitroaniline

Single crystals of m‐Nitroaniline (mNA) were grown by slow cooling solution growth technique. Induction period, interfacial energy and metastable zonewidth have been evaluated. The solubility of mNA has been estimated at different temperatures in acetone and ethanol. Interfacial energy has been estimated using the experimentally determined induction period values. It is observed that the nucleation rate increases with the increase of supersaturation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Acoustic and Thermodynamic Properties of Binary Liquid Mixtures of Benzaldehyde in Hexane and Cyclohexane

Densities and ultrasonic speeds of binary mixtures of benzaldehyde with n-hexane and cyclohexane at 30 °C were measured over the entire composition range. From these experimental data, the adiabatic compressibility (K _S ), intermolecular free length (L _f), acoustic impedance (Z), relative association (R _a) and relaxation strength (r) were calculated. Also, the excess adiabatic compressibility (K _S ^E), intermolecular free length (L _f^E), acoustic impedance (Z ^E), and ultrasonic velocity (U ^E) were calculated. The observed variation of these parameters helps in understanding the nature of interactions in these mixtures. Further, theoretical values of the ultrasonic speed were evaluated using theories and empirical relations. The relative merits of these theories and relations were discussed.     

Optical absorption and EPR studies on some natural carbonate minerals

Limestone and dolomite minerals have been investigated by EPR and optical absorption studies. The optical absorption results indicate the presence of ferrous and ferric ion in both the minerals. The bands observed at 24,750, 22,780, 19,415 and 14,450cm(-1) are assigned to 6A1-->4T2 (4D), 6A1-->4E, 4A1 (4G), 6A1-->4T2 (4G) and 6A1-->4T1 (4G) d-d transitions of Fe3+ ions, respectively. A low energy band at 10,638cm(-1) is identified as being due to Fe2+ ion and can be attributed to 5T2g-->5E(g) transition. The weak band in the region 30,000-40,000cm(-1) corresponds to Fe-O charge transfer. Crystal field and Racah parameters evaluated for the Fe2+ ion are Dq=990cm(-1), B=885cm(-1) and C=3860cm(-1) and that for Fe3+ ions are Dq=1040cm(-1), B=703cm(-1) and C=3150cm(-1). The room temperature 9 and 35GHz EPR spectra of the minerals exhibit a sextet hyperfine pattern characteristic of Mn2+. The EPR parameters obtained for Mn2+ in limestone are g=2.00399, A= -9.411mT, D= -8.19mT and these values confirm that the Mn2+ ion are located in the calcite impurity. For Mn2+ in dolomite are g=2.0004, A= -9.45mT for Mn2+ substituted in the Ca lattice site and g=2.00984, A= -9.37mT, D= -9.94mT for substitution at the Mg site. The EPR spectra of heat-treated limestone and dolomite samples at 950 degrees C show a signal corresponding to CO2(-) ion.     

Biological Real-Time Reaction Calorimeter Studies for the Production of Penicillin G Acylase from Bacillus badius

Penicillin G acylase (PGA) is a commercially important enzyme that cleaves penicillin G to 6-amino penicillanic acid (6-APA) and phenyl acetic acid (PAA). The strain Bacillus badius has been identified as potential producer of PGA. A detailed calorimetric investigation on PGA production was carried out to enable generation of thermokinetic data possible for commercial application. Reaction calorimetric studies coupled with respirometric studies suggested that enzyme activity of the species B. badius was calorimetrically traceable. Three phases of growth were distinctly noticeable in the metabolic heat-time curve. Increase in enzymatic activity with restricted growth confirmed intracellular nature of the production process. The estimated heat yields due to biomass growth, 10.026 kJ/g, substrate consumption 22.761 kJ/g, and oxygen uptake 383?±?10 kJ/mol helped to understand the energetic of the organism under study. Low oxycalorific coefficient confirmed the existence of fermentation-coupled metabolism of B. badius.     

Vibrational spectroscopy investigation using ab initio and density functional theory on p-anisaldehyde

The FTIR and FT Raman spectra of p-anisaldehyde has been recorded in the regions 4,000-400 and 3,500-100 cm(-1), respectively. The optimized geometry, frequency and intensity of the vibrational bands of p-anisaldehyde were obtained by ab initio and DFT levels of theory with complete relaxation in the potential energy surface using 6-31G(d,p) basis set. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. The harmonic vibrational frequencies calculated have been compared with experimental FTIR and FT Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed bar type spectrograms.