Synthesis, structure and spectroscopic studies on hydroxo-bridged heterotrinuclear complexes of cobalt(m) with ethane-l,2-diamine and ammonia as terminal ligands

Hydroxo-bridged homo- and hetero-trinuclear cobalt(III) complexes of the type [MII(H2O)2{(OH)2CoIII(N4)}2]X2·nH2O [MII= a divalent metal ion such as CoII, NiII or ZnII; N4=(en)2(en = ethane-1,2-diamine) or (NH3)4; X = SO4 or (ClO4)2; n= 3 or 5] have been prepared and spectroscopically characterized. The structure of [Cu{(OH)2Co(en)2}2][SO4]2·2H2O 1 has been determined. The geometry around copper atom is a pseudo-square-based pyramid, with the basal sites occupied by four bridging hydroxide oxygens and the apical site is occupied by a weakly co-ordinated sulfate anion [Cu–O 2.516(4)Å]. The hydroxo groups bridge pairs of cobalt(III) ions which are in near-octahedral environments. The ethylenediamine chelate rings have the twist conformation. In the crystal structure of [Cu{(OH)2Co(en)2}2][ClO4]4·2H2O 2 the perchlorate ion is not co-ordinated and the en ligands have envelope conformations. The sulfate ion in [Cu{(OH)2Co(NH3)4}2][SO4]2·4H2O 3 is not co-ordinated to the central copper ion. Electronic, infrared and variable-temperature EPR spectral data are discussed.

Isolation and characterization of binding proteins for retinol from the cytosol, nucleosol and chromatin of the oviduct magnum of laying hens

Protein fractions that bind retinol were isolated from the cytosol, nucleosol and chromatin of the oviduct magnum of laying hens. The proteins isolated from the three sources showed similar elution profiles on chromatography through Sephadex G-75 and G-50 columns, and comparable mobility during electrophoresis on sodium dodecyl sulphate/polyacrylamide gels. Their molecular weights were calculated to be around 14500. When oviducts from vitamin A-depleted and vitamin A-repleted immature chicks given oestrogen injections for 6 consecutive days were incubated with [3H]retinyl acetate, uptake of the radioactivity in the nuclei of the vitamin A-depleted tissue was severalfold higher than that in the nuclei from the vitamin A-repleted tissue.

7Li Spin-flip satellites in the EPR sectra of NH3+ -doped LiKSO4

EPR spectra of lithium potassium sulfate doped with NH3+ have been recorded at 9.05 GHz. A pair of satellites can be seen symmetrically situated on either side of the main lines. The separation of the satellite lines from the main line corresponds to the 7Li NMR frequency. The distance of the interacting 7Li nucleus from the unpaired electron in NH3+ is estimated to be 3.29 Å.

Purification and properties of riboflavin-binding protein from the egg white of the duck (Anas platyrhynckos).

Riboflavin-binding protein was purified from the egg white of domestic duck and some of its properties were investigated. The protein was homogeneous by the criteria of gel filtration on Sephadex G-100 and electrophoresis on sodium dodecyl sulphate-polyacrylamide gels, had molecular weight of 36 000 ± 1000 and, unlike the chicken egg white protein (Mr 32 000 ± 2000), was devoid of covalently-bound carbohydrate. It was similar to the chicken riboflavin-binding protein in its behavior on ion-exchange celluloses and affinity to interact with the flavin and its coenzymes, but differed significantly in amino acid composition in that it completely lacked proline and contained less of methionine and arginine. The protein partially cross-reacted with the specific antiserum to chicken riboflavin-binding protein with a spur during immunodiffusion analysis.

Cuprous oxide catalyzed air oxidation of thiosulfate and tetrathionate

Thiosulfate (S2O32−) and tetrathionate (S4O62−)are oxidized to sulfate by air at atmospheric pressure and 50–70°C in the presence of cuprous oxide (Cu2O) as catalyst. Sulfate is produced from S2O32− by series-parallel reaction paths involving S4O62− as an intermediate. The rate data obtained for air oxidation of S2O32− on Cu2O agree well with a pseudo-homogeneous first order kinetic scheme, yielding values of rate constants for series parallel reaction paths which have been used in modelling the catalyzed air oxidation of S2O32−. Air oxidation of S4O62− on Cu2O proceeds at a higher rate in the presence of S2O32− than in its absence. Cu2O is less active than Cu2S for the air oxidation of S2O32−, as shown by the rate constant values which for Cu2O catalyzed oxidation are an order of magnitude smaller than those for the Cu2S catalyzed oxidation.

Precipitation of rutile and anatase (Tio12) fine powders and their conversion to MTiO3 (M = Ba, Sr, Ca) by the hydrothermal method

Fine powders of TiO2 (rutile) with high degree of crystallinity are formed from aqueous titanium oxychloride solution under hydrothermal conditions at 160–230°C and 15–100 kg/cm2 for 1–2 hours. The anatase phase is produced from the same medium when sulfate ion impurity is present, with Image . Both these fine powders are converted to BaTiO3, SrTiO3 or CaTiO3 when suspended in Ba(OH)2 or Sr(OH)2 solution or in an aqueous slurry of carbonate-free CaO with Image , at 180–280°C and 12–65 kg/cm2 for 4–8 hours. The resulting fine powders contain monocrystallites of the perovskite phase with 0.1–1.5 μm particle size.

Sacrificial photolysis of water on TiO2 fine powders prepared by the hydrothermal method

The often discussed role of surface hydroxylation of TiO2 particles as an essential characterestics for their photocatalytic activity can be verified by preparing TiO2 powders by hydrothermal method since hydroxylated surface layers will be better retained on these particles formed in superheated water. Thus, fine powders of TiO2 (rutile) with high degree of crystallinity are formed from titanium oxychloride in the mixed solvent of water and 2-propanol at 160–230°C and 20–120 atm. The anatase phase is produced from the same medium when sulfate ion impurity is present, with Image . TiO2 powders are washed free of anions and 2-propanol by ultrafiltration and are Pt mounted by a photochemical method. Aqueous suspensions of both forms of TiO2 neither as such nor after Pt-loading, do not produce H2 on band gap illumination whereas, H2 is generated in presence of hole scavengers such as EDTA, TEOA, sulfite or hypophosphite. The effects of hole scavenger concentration, Pt : TiO2 ratio, particulate suspension density and the nature of hole scavengers on H2 production are presented. Platinised rutile powders are equally active as anatase in sacrificial systems.

Isolation and characterization of riboflavin-binding protein from pregnant-rat serum

A high-affinity riboflavin -binding protein was isolated and characterized for the first time from pregnant-rat sera by affinity chromatography on a lumiflavin-agarose column. The purified protein was homogeneous by the criteria of analytical polyacrylamide-gel disc electrophoresis, gel-filtration chromatography on Sephadex G-100 and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. It had a molecular weight of 90000+/-5000 and interacted with [14C]riboflavin with a 1:1 molar ratio with a dissociation constant (Kd) of 0.42 micron.

Allosteric regulation of serine hydroxymethyltransferase from mung bean (Phaseolus aureus)

Serine hydroxymethyltransferase, the first enzyme in the pathway for the interconversion of one carbon compounds was purified from mung bean seedlings by ammonium sulfate fractionation, DEAE-Sephadex, Blue Sepharose CL-6B affinity chromatography and gel filteration on Sephacryl S-200. The specific activity of the enzyme, 0.73 (u mol HCHO formed/min/mg protein) was 104 times larger than the highest value reported hitherto. Saturation of tetrahydrofolate was sigmoid, whereas with serine was hyperbolic, with nH values of 1.9 and 1.0 respectively. Reduced nicotinamide adenine dinucleotide, lysine and methionine decreased, whereas nicotinamide adenine dinucleotide, adenosine 5′-monophosphate and adenosine 5′-triphosphate increased the sigmoidicity. These results suggest that serine hydroxymethyltransferase from mung bean is a regulatory enzyme. H4folate; (±)-L-tetrahydrofolate

A chitotetrose specific lectin from Luffa acutangula :Physico-chemical properties and the assignment of orientation of sugars in the lectin binding site

A chitooligosaccharide specific lectin (Luffa acutangula agglutinin) has been purified from the exudate of ridge gourd fruits by affinity chromatography on soybean agglutininglycopeptides coupled to Sepharose-6B. The affinity purified lectin was found homogeneous by polyacrylamide gel electrophoresis, in sodium dodecyl sulphate-polyacrylamide gels, by gel filtration on Sephadex G-100 and by sedimentation velocity experiments. The relative molecular weight of this lectin is determined to be 48,000 ± 1,000 by gel chromatography and sedimentation equilibrium experiments. The sedimentation coefficient (S20, w) was obtained to be 4·06 S. The Stokes’ radius of the protein was found to be 2·9 nm by gel filtration. In sodium dodecyl sulphate-polyacrylamide gel electrophoresis the lectin gave a molecular weight of 24,000 in the presence as well as absence of 2-mercaptoethanol. The subunits in this dimeric lectin are therefore held by non-covalent interactions alone. The lectin is not a glycoprotein and circular dichroism spectral studies indicate that this lectin has 31% α-helix and no ß-sheet. The lectin is found to bind specifically to chitooligosaccharides and the affinity of the lectin increases with increasing oligosaccharide chain length as monitored by near ultra-violetcircular dichroism and intrinsic fluorescence titration. The values of ΔG, ΔΗ and ΔS for the binding process showed a pronounced dependence on the size of the oligosaccharide. The values for both ΔΗ and ΔS show a significant increase with increase in the oligosaccharide chain length showing that the binding of higher oligomers is progressively more favoured thermodynamically than chitobiose itself. The thermodynamic data is consistent with an extended binding site in the lectin which accommodates a tetrasaccharide. Based on the thermodynamic data, blue shifts and fluorescence enhancement, spatial orientation of chitooligosaccharides in the combining site of the lectin is assigned.

Enzymatic cleavage of carotenoids

1. 1.|Carotene 15,15′-dioxygenase (EC 1.13.11.21) has been isolated from the intestine of guinea pig and rabbit and purified 38- and 30-fold, respectively, but subjecting the intestinal homogenate to protamine sulfate treatment, (NH4)2SO4 fractionation and acetone precipitation. 2. 2.|The guinea pig enzyme showed a pH optimum at 8.5, an optimum substrate concentration of 200 nmoles of β,β-carotene per 25 ml of reaction mixture, an apparent Km with β,β-carotene as substrate of 9.5 · 10−6 M and a V 3.3 nmoles of retinal formation/mg protein per h. The reaction was linear upto 3 h and the reaction rate increased linearly with increase in enzyme protein concentration. The enzyme was activated by GSH and Fe2+ and inhibited by sodium dodecylsulfate, sulfhydryl binding and iron chelating agents. 3. 3.|The reaction catalysed by guinea pig enzyme was strictly stoichiometric. 4. 4.|Rabbit enzyme showed a close similarity with guinea pig enzyme with respect to time course, optimum substrate concentration, activation by Fe2+ and GSH, inhibition by sodium dodecylsulfate, iron chelating and sulfhydryl binding agents. However, it showed a slightly lower pH optimum (pH 7.8). 5. 5.|The enzyme from guinea pig and rabbit showed remarkable similarity with respect to cleavage of carotenoids. The enzyme from both the species was more specific for β,β-carotene but could also cleave a number of other carotenoids at the 15,15′-double bond. 6. 6.|10′-Apo-β-carotenal and 10′-apo-β-carotenol were readily cleaved compared with other apo-β-carotenals and apo-β-carotenols tested. 7. 7.|It has been conclusively shown for the first time that mono-ring substituted carotenoids are also cleaved at the 15,15′-double bond.

Stable Dispersions of Metal Oxide Nanowires and Nanoparticles in Water, Dimethylformamide and Toluene

In view of the important need to generate well-dispersed inorganic nanostructures in various solvents, we have explored the dispersion of nanostructures of metal oxides such as TiO2, Fe3O4 and ZnO in solvents of differing polarity in the presence of several surfactants. The solvents used are water, dimethylformamide (DMF) and toluene. The surfactant-solvent combinations yielding the best dispersions are reported alongwith some of the characteristics of the nanostructures in the dispersions. The surfactants which dispersed TiO2 nanowires in water were polyethylene oxide (PEO), Triton X-100 (TX-100), polyvinyl alcohol (PVA) and sodium bis(2-ethylhexyl) sulphosuccinate (AOT). TiO2 nanoparticles could also be dispersed with AOT and PEO in water, and with AOT in toluene. In DMF, PVA, PEO and TX-100 were found to be effective, while in toluene, only AOT gave good dispersions. Fe3O4 nanoparticles were held for long periods of time in water by PEO, AOT, PVA and polyethylene glycol (PEG), and by AOT in toluene. In the case of ZnO nanowires, the best surfactant-solvent combinations were found to be, PEO, sodium dodecyl sulphate (SIDS) and AOT in water and AOT, PEG, PVA, PEO and TX-100 in DMF In toluene, stable dispersions of ZnO nanowires were obtained with PEO. We have also been able to disperse oxide nanostructures in non-polar solvents by employing a hydrophobic silane coating on the surface.

Enzymatic cleavage of carotenoids

1. 1.|Carotene 15,15′-dioxygenase (EC 1.13.11.21) has been isolated from the intestine of guinea pig and rabbit and purified 38- and 30-fold, respectively, but subjecting the intestinal homogenate to protamine sulfate treatment, (NH4)2SO4 fractionation and acetone precipitation. 2. 2.|The guinea pig enzyme showed a pH optimum at 8.5, an optimum substrate concentration of 200 nmoles of β,β-carotene per 25 ml of reaction mixture, an apparent Km with β,β-carotene as substrate of 9.5 · 10−6 M and a V 3.3 nmoles of retinal formation/mg protein per h. The reaction was linear upto 3 h and the reaction rate increased linearly with increase in enzyme protein concentration. The enzyme was activated by GSH and Fe2+ and inhibited by sodium dodecylsulfate, sulfhydryl binding and iron chelating agents. 3. 3.|The reaction catalysed by guinea pig enzyme was strictly stoichiometric. 4. 4.|Rabbit enzyme showed a close similarity with guinea pig enzyme with respect to time course, optimum substrate concentration, activation by Fe2+ and GSH, inhibition by sodium dodecylsulfate, iron chelating and sulfhydryl binding agents. However, it showed a slightly lower pH optimum (pH 7.8). 5. 5.|The enzyme from guinea pig and rabbit showed remarkable similarity with respect to cleavage of carotenoids. The enzyme from both the species was more specific for β,β-carotene but could also cleave a number of other carotenoids at the 15,15′-double bond. 6. 6.|10′-Apo-β-carotenal and 10′-apo-β-carotenol were readily cleaved compared with other apo-β-carotenals and apo-β-carotenols tested. 7. 7.|It has been conclusively shown for the first time that mono-ring substituted carotenoids are also cleaved at the 15,15′-double bond.

Vanadate-stimulated NADH oxidation in plasma membrane

The rate of NADH oxidation with oxygen as the acceptor is very low in mouse liver plasma membrane and erythrocyte membrane. When vanadate is added, this rate is stimulated 10- to 20-fold. The absorption spectrum of vanadate does not change with the disappearance of NADH. The reaction is inhibited by superoxide dismutase, and there is no activity under an argon atmosphere. This indicates that oxygen is the electron acceptor and the reaction is mediated by superoxide. The vanadate stimulation is not limited to plasma membrane. Golgi apparatus and endoplasmic reticulum show similar increase in NADH oxidase activity when vanadate is added. The endomembranes have significant vanadate-stimulated activity with both NADH and NADPH. The vanadate-stimulated NADH oxidase in plasma membrane is inhibited by compounds, which inhibit NADH dehydrogenase activity: catechols, anthracycline drugs and manganese. This activity is stimulated by high phosphate and sulfate anion concentrations.

Transport of retinol in the duck plasma

Retinol-binding protein and prealbumin were isolated from duck plasma by chromatography on DEAE-cellulose-and DEAE-Sephadex A-50, gel filtration on Sephadex G- 100 and preparative Polyacrylamide gel electrophoresis. The molecular weights of the retinolbinding protein-prealbumin complex, prealbumin and retinol-binding protein were found to be 75,000, 55,0000 and 20,000, respectively. On sodium dodecyl sulphate Polyacrylamide gel electrophoresis, prealbumin dissociated into identical subunits exhibiting a molecular weight of 13,500. Retinol-binding protein exhibited microheterogeneity on electrophoresis, whereas prealbumin moved as a single band unlike the multiple bands observed in chicken and rat.The ultraviolet and fluorescence spectra of the two proteins were similar to those isolated from other species. No carbohydrate moiety was detected in either retinol-binding protein or prealbumin. Duck retinol-binding protein and prealbumin showed cross-reactivity with their counterparts in chicken but differed immunologically from those of goat and man. Retinolbinding protein and prealbumin could be dissociated at low ionic strength, in 2M urea, by CMsephadex chromatography or on preparative electrophoresis. Although the transport of retinol in duck plasma is mediated by carrier proteins as in other species, it is distinguished by the absence of microheterogeneity in prealbumin and of an apo-retinol-binding protein form that could be transported in the plasma.