Role of Capping Ligands on the Nanoparticles in the Modulation of Properties of a Hybrid Matrix of Nanoparticles in a 2D Film and in a Supramolecular Organogel

We incorporate various gold nanoparticles (AuNPs) capped with different ligands in two-dimensional films and three-dimensional aggregates derived from N-stearoyl-L-alanine and N-lauroyl-L-alanine, respectively. The assemblies of N-stearoyl-L-alanine afforded stable films at the air-water interface. More compact assemblies were formed upon incorporation of AuNPs in the air-water interface of N-stearoyl-L-alanine. We then examined the effects of incorporation of various AuNPs functionalized with different capping ligands in three-dimensional assemblies of N-lauroyl-L-alanine, a compound that formed a gel in hydrocarbons. The profound influence of nanoparticle incorporation into physical gels was evident from evaluation of various microscopic and bulk properties. The interaction of AuNPs with the gelator assembly was found to depend critically on the capping ligands protecting the Au surface of the gold nanoparticles. Transmission electron microscopy (TEM) showed a long-range directional assembly of certain AuNPs along the gel fibers. Scanning electron microscopy (SEM) images of the freeze-dried gels and nanocomposites indicate that the morphological transformation in the composite microstructures depends significantly on the capping agent of the nanoparticles. Differential scanning calorimetry (DSC) showed that gel formation from sol occurred at a lower temperature upon incorporation of AuNPs having capping ligands that were able to align and noncovalently interact with the gel fibers. Rheological studies indicate that the gel-nanoparticle composites exhibit significantly greater viscoelasticity compared to the native gel alone when the capping ligands are able to interact through interdigitation into the gelator assembly. Thus, it was possible to define a clear relationship between the materials and the molecular-level properties by means of manipulation of the information inscribed on the NP surface.

Purification and properties of a DNA polymerase from Mycobacterium tuberculosis H37Rv

DNA polymerase has been purified approximately 2000-fold from Mycobacterium tuberculosis H37Rv. The purified preparation was homogeneous by electrophoretic criteria and has a molecular weight of 135 000. The purified enzyme resembles Escherichia coli polymerase I in its properties, being insensitive to sulfhydryl drugs and possessing 5′,3′-exonuclease activity in addition to polymerase and 3′,5′-exonuclease activities. However, it differs from the latter in its sensitivity to higher salt concentration and DNA intercalating agents such as 8-aminoquinoline. The polymerase exhibited maximal activity between 37–42°C and pH 8.8–9.5. The polymerase was stable for several months below 0°C. However, the 5′,3′-exonuclease activity was more labile. The effects of different metal ions, polyamines and drugs on the polymerase activity are presented.

Purification and properties of benzoate-4-hydroxylase from a soil pseudomonad

Benzoate-4-hydroxylase from a soil pseudomonad was isolated and purified about 50-fold. Polyacrylamide gel electrophoresis of this enzyme preparation showed one major band and one minor band. The approximate molecular weight of the enzyme was found to be 120,000. Benzoate-4-hydroxylase was most active around pH 7.2. The enzyme showed requirements for tetrahydropteridine as the cofactor and molecular oxygen as the electron acceptor. NADPH, NADH, dithiothreitol, β-mercaptoethanol, and ascorbic acid when added alone to the reaction mixture did not support the hydroxylation reaction to any significant extent. However, when these compounds were added together with tetrahydropteridine, they stimulated the hydroxylation. This stimulation is probably due to the reduction of the oxidized pteridine back to the reduced form. This enzyme was activated by Fe2+ and benzoate. It was observed that benzoate-4-hydroxylase could catalyze the oxidation of NADPH in the presence of benzoate,p-aminobenzoate, p-nitrobenzoate, p-chlorobenzoate, and p-methylbenzoate, with only benzoate showing maximum hydroxylation. Inhibition studies with substrate analogs and their kinetic analysis revealed that the carboxyl group is involved in binding the substrate to the enzyme at the active center. The enzyme catalyzed the conversion of 1 mol of benzoate to 1 mol of p-hydroxybenzoate with the consumption of slightly more than 1 mol of NADPH and oxygen.

Characterisation of wood–water relationships and transverse anatomy and their relationship to drying degrade

Characterisation of a number of key wood properties utilising ‘state of the art’ tools was achieved for four commercial Australian hardwood species: Corymbia citriodora, Eucalyptus pilularis, Eucalyptus marginata and Eucalyptus obliqua. The wood properties were measured for input into microscopic (cellular level) and macroscopic (board level) vacuum drying models currently under development. Morphological characterisation was completed using a combination of ESEM, optical microscopy and a custom vector-based image analysis software. A clear difference in wood porosity, size, wall thickness and orientation was evident between species. Wood porosity was measured using a combination of fibre and vessel porosity. A highly sensitive microbalance and scanning laser micrometres were used to measure loss of moisture content in conjunction with directional shrinkage on micro-samples of E. obliqua to investigate the validity of measuring collapse-free shrinkage in very thin sections. Collapse-free shrinkage was characterised, and collapse propensity was verified when testing thicker samples. Desorption isotherms were calculated for each species using wood–water relations data generated from shrinkage experiments. Fibre geometry and wood shrinkage anisotropy were used to explain the observed difficulty in drying of the different species in terms of collapse and drying stress-related degrade.

Preparation, properties and metabolism of retinoic acid anhydride.

A new analogue of vitamin A, viz., retinoic acid anhydride was prepared, for the first time, by the action of thionyl chloride on retinoic acid in benzene containing pyridine. The amhydride was charcterised by its chromatographic properties, elemental analysis, ultraviolet absorption, infrared and nuclear magnetic resonance spectral characteristics. The compound could be readily hydrolysed to retinoic acid both by acid and alkali treatments and reduced by lithium aluminium hydride to vitamin A alcohol (retinol). The spectral changes with antimony trichloride reagent were similar to those observed for retinoic acid. The metabolism of retinoic acid anhydride was found to be similar to that of retinoic acic. When administered either orally or intraperitoneally, the compound promotes growth in vitamin A-deficient rats. Time-course experiments revealed that retinoic acid anhydride is converted into retinoic acid by non-enzymatic hydrolysis and thereby exerts its biological activity. The biopotency of the anhydride was found to be nearly the same as that of the acid. A new method of preparing esters of retinoic acid employing retinoic acid anhydride as an intermediate, has been described.

Coordination properties of vic-isonitrosoimines in their copper (II) and palladium (II) complexes

Preparation and structural characterization of palladium (II) complexes of ligands III-V and copper (II) complexes of III are reported. The elemental analyses of the complexes show that the metal: ligand ratio is 1 : 2. The electrical conductance in acetone shows the non-electrolytic nature of the complexes. The diamagnetic character suggests a gross square-planar geometry for the palladium (II) complexes. Copper (II) complexes are paramagnetic with/~eff.~l'90 B.M. Spectral data suggest that in all the complexes the ligand coordinates to the metal (II) symmetrically through isonitroso-nitrogen and imine-nitrogen, forming a ¡ membered chelate ring. Amine-exchange reactions of the complexes are discussed and compared on the basis of their structures.

A new mode of ring cleavage of 2,3-dihydroxybenzoic acid in Tecoma stans (L.). Partial purification and properties of 2,3-dihydroxybenzoate 2,3-oxygenase.

2,3-Dihydroxybenzoic acid has been shown to be oxidized via the 3-oxoadipate pathway in the leaves of Tecoma stans. The formation of 2-carboxy-cis,cis-muconic acid, a muconolactone, 3-oxoadipic acid and carbon dioxide during its metabolism has been demonstrated using an extract of Tecoma leaves. The first reaction of the pathway, viz., the conversion of 2,3-dihydroxybenzoate to 2-carboxy-cis,cis-muconic acid has been shown to be catalysed by an enzyme designated as 2,3-dihydroxybenzoate 2,3-oxygenase. The enzyme has been partially purified and a few of its properties studied. The enzyme is very labile with a half-life of 3--4 h. It is maximally active with 2,3-dihydroxybenzoate as the substrate and does not exhibit any activity with catechol, 4-methyl catechol, 3,4-dihydroxybenzoic acid, etc. However, 2,3-dihydroxy-p-toluate and 2,3-dihydroxy-p-cumate are also oxidized by the enzyme by about 38% and 28% respectively, compared to 2,3-dihydroxybenzoate. Sulfhydryl reagents inhibit the enzyme reaction and the inhibition can be prevented by preincubation of the enzyme with the substrate. Substrate also affords protection to the enzyme against thermal inactivation. Sulfhydryl compounds strongly inhibit the reaction and the inhibition cannot be prevented by preincubation of the enzyme with its substrates. Data on the effect of metal ions as well as metal chelating agents suggest that copper is the metal cofactor of the enzyme. Evidence is presented which suggests that iron may not be participating in the overall catalytic mechanism.

Psychometric properties of the DCDDaily-Q: A new parental questionnaire on children's performance in activities of daily living

Difficulties in the performance of activities of daily living (ADL) are a key feature of developmental coordination disorder (DCD). The DCDDaily-Q was developed to address children's motor performance in a comprehensive range ADL. The aim of this study was to investigate the psychometric properties of this parental questionnaire. Parents of 218 five to eight year-old children (DCD group: N=25; reference group: N=193) completed the research version of the new DCDDaily-Q and the Movement Assessment Battery for Children-2 (MABC2) Checklist and Developmental Coordination Disorder Questionnaire (DCDQ). Children were assessed with the MABC2 and DCDDaily. Item reduction analyses were performed and reliability (internal consistency and factor structure) and concurrent, discriminant, and incremental validity of the DCDDaily-Q were investigated. The final version of the DCDDaily-Q comprises 23 items that cover three underlying factors and shows good internal consistency (Cronbach's α>.80). Moderate correlations were found between the DCDDaily-Q and the other instruments used (p<.001 for the reference group; p>.05 for the DCD group). Discriminant validity of the DCDDaily-Q was good for DCDDaily-Q total scores (p<.001) and all 23 item scores (p<.01), indicating poorer performance in the DCD group. Sensitivity (88%) and specificity (92%) were good. The DCDDaily-Q better predicted DCD than currently used questionnaires (R2=.88). In conclusion, the DCDDaily-Q is a valid and reliable questionnaire to address children's ADL performance.

Development and psychometric properties of the DCDDaily: a new test for clinical assessment of capacity in activities of daily living in children with developmental coordination disorder

Objective To develop the DCDDaily, an instrument for objective and standardized clinical assessment of capacity in activities of daily living (ADL) in children with developmental coordination disorder (DCD), and to investigate its usability, reliability, and validity. Subjects Five to eight-year-old children with and without DCD. Main measures The DCDDaily was developed based on thorough review of the literature and extensive expert involvement. To investigate the usability (assessment time and feasibility), reliability (internal consistency and repeatability), and validity (concurrent and discriminant validity) of the DCDDaily, children were assessed with the DCDDaily and the Movement Assessment Battery for Children-2 Test, and their parents filled in the Movement Assessment Battery for Children-2 Checklist and Developmental Coordination Disorder Questionnaire. Results 459 children were assessed (DCD group, n = 55; normative reference group, n = 404). Assessment was possible within 30 minutes and in any clinical setting. For internal consistency, Cronbach’s α = 0.83. Intraclass correlation = 0.87 for test–retest reliability and 0.89 for inter-rater reliability. Concurrent correlations with Movement Assessment Battery for Children-2 Test and questionnaires were ρ = −0.494, 0.239, and −0.284, p < 0.001. Discriminant validity measures showed significantly worse performance in the DCD group than in the control group (mean (SD) score 33 (5.6) versus 26 (4.3), p < 0.001). The area under curve characteristic = 0.872, sensitivity and specificity were 80%. Conclusions The DCDDaily is a valid and reliable instrument for clinical assessment of capacity in ADL, that is feasible for use in clinical practice.

Thermodynamic properties of the system toluene-1,2-dichloroethane

Data on heats of mixing at 30 'C, vapor-liquid equilibrium, latent heats of vaporization at 686 mmHg, and vapor pressures for the system toluene-l,2-dichloroethane are presented.

Purification and Properties of l-4-Hydroxymandelate Oxidase from Pseudomonas convexa

An inducible membrane-bound l-4-hydroxymandelate oxidase (decarboxylating) from Pseudomonas convexa has been solubilized and partially purified. It catalyzes the conversion of l-4-hydroxymandelic acid to 4-hydroxybenzaldehyde in a single step with the stoichiometric consumption of O2 and liberation of CO2. The enzyme is optimally active at pH 6.6 and at 55 oC. It requires FAD and Mn2+ for its activity. The membrane-bound enzyme is more stable than the solubilized and purified enzyme. After solubilization it gradually loses its activity when kept at 5 oC which can be fully reactivated by freezing and thawing. The Km values for DL-4-hydroxymandelate and FAD are 0.44 mM and 0.038 mM respectively. The enzyme is highly specific for DL-4-hydroxymandelic acid. DL-3,4-Dihydroxymandelic acid competitively inhibited the enzyme reaction. From the Dixon plot the Ki for DL-3,4-dihydroxymandelic acid was calculated to be 1.8 × 10−4 M. The enzyme is completely inactivated by thiol compounds and not affected by thiol inhibitors. The enzyme is also inhibited by denaturing agents, heavy metal ions and by chelating agents.

Microbial L-phenylalanine ammonia-lyase. Purification, subunit structure and kinetic properties of the enzyme from Rhizoctonia solani

Phenylalanine ammonia-lyase (EC 4.3.1.5) was purified to homogeneity from the acetone-dried powders of the mycelial felts of the plant pathogenic fungus Rhizoctonia solani. 2. A useful modification in protamine sulphate treatment to get substantial purification of the enzyme in a single-step is described. 3. The purified enzyme shows bisubstrate activity towards L-phenylalanine and L-tyrosine. 4. It is sensitive to carbonyl reagents and the inhibition is not reversed by gel filtration. 5. The molecular weight of the enzyme as determined by Sephadex G-200 chromatography and sucrose-density-gradient centrifugation is around 330000. 6. The enzyme is made up of two pairs of unidentical subunits, with a molecular weight of 70000 (alpha) and 90000 (beta) respectively. 7. Studies on initial velocity versus substrate concentration have shown significant deviations from Michaelis-Menten kinetics. 8. The double-reciprocal plots are biphasic (concave downwards) and Hofstee plots show a curvilinear pattern. 9. The apparent Km value increases from 0.18 mM to as high as 5.0 mM with the increase in the concentration of the substrate and during this process the Vmax, increases by 2-2.5-fold. 10. The value of Hill coefficient is 0.5. 11. Steady-state rates of phenylalanine ammonia-lyase reaction in the presence of inhibitors like D-phenylalanine, cinnamic, p-coumaric, caffeic, dihydrocaffeic and phenylpyruvic acid have shown that only one molecule of each type of inhibitor binds to a molecule of the enzyme. These observations suggest the involvement of negative homotropic interactions in phenylalanine ammonia-lyase. 12. The enzyme could not be desensitized by treatment with HgCl2, p-chloromercuribenzoic acid or by repeated freezing and thawing.

The purification and properties of peroxidase in Mycobacterium tuberculosis H37Rv and its possible role in the mechanism of action of isonicotinic acid hydrazide

Peroxidase from Mycobacterium tuberculosis H37Rv was purified to homogeneity. The homogeneous protein exhibits catalase and Y (Youatt's)-enzyme activities in addition to peroxidase activity. Further confirmation that the three activities are due to a single enzyme was accomplished by other criteria, such as differential thermal inactivation, sensitivity to different inhibitors, and co-purification. The Y enzyme (peroxidase) was separated from NADase (NAD+ glycohydrolase) inhibitor by gel filtration on Sephadex G-200. The molecular weights of peroxidase and NADase inhibitor, as determined by gel filtration, are 240000 and 98000 respectively. The Y enzyme shows two Km values for both isoniazid (isonicotinic acid hydrazide) and NAD at low and high concentrations. Analysis of the data by Hill plots revealed that the enzyme has one binding site at lower substrate concentrations and more than one at higher substrate concentration. The enzyme contains 6g-atoms of iron/mol. Highly purified preparations of peroxidases from different sources catalyse the Y-enzyme reaction, suggesting that the nature of the reaction may be a peroxidatic oxidation of isoniazid. Moreover, the Y-enzyme reaction is enhanced by O2. Isoniazid-resistant mutants do not exhibit Y-enzyme, peroxidase or catalase activities, and do not take up isoniazid. The Y-enzyme reaction is therefore implicated in the uptake of the drug.

Thermodynamic properties of toluene-1,1,2,2-tetrachloroethane

Data on heats of mixing at 298.15 and 308.15 K, vaporliquid equilibria, latent heats of vaporization at 686 mmHg, and vapor pressures for the system toluene-1,1,2,2- tetrachloroethane are presented. The effect of alkyl substitution on heats of mixing is discussed.