Using leucine-p-nitroanilide (Leu-pNA) as a substrate, we demonstrated aminopeptidase activity in the culture filtrates of several Pseudomonas aeruginosa strains. The aminopeptidase was partially purified by DEAE-cellulose chromatography and found to be heat stable. The apparent molecular mass of the enzyme was ϳ56 kDa; hence, it was designated AP 56 . Heating (70°C) of the partially purified aminopeptidase preparations led to the conversion of AP 56 to a ϳ28-kDa protein (AP 28 ) that retained enzyme activity, a reaction that depended on elastase (LasB). The pH optimum for Leu-pNA hydrolysis by AP 28 was 8.5. This activity was inhibited by Zn chelators but not by inhibitors of serine-or thiol-proteases, suggesting that AP 28 is a Zn-dependent enzyme. Of several amino acid p-nitroanilide derivatives examined, Leu-pNA was the preferred substrate. The sequences of the first 20 residues of AP 56 and AP 28 were determined. A search of the P. aeruginosa genomic data base revealed a perfect match of these sequences with positions 39 -58 and 273-291, respectively, in a 536-amino acid residue open reading frame predicted to encode an aminopeptidase. A search for sequence similarities with other proteins revealed 52% identity with Streptomyces griseus aminopeptidase, ϳ35% identity with Saccharomyces cerevisiae aminopeptidase Y and a hypothetical aminopeptidase from Bacillus subtilis, and 29 -32% with Aeromonas caviae, Vibrio proteolyticus, and Vibrio cholerae aminopeptidases. The residues potentially involved in zinc coordination were conserved in all these proteins. Thus, P. aeruginosa aminopeptidase may belong to the same family (M28) of metalloproteases.

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The electrochemical urea oxidation reaction (UOR) is considered as a promising renewable source for harvesting energy from waste. We report a new synthetic design approach to produce an iron−nickel alloy nanocatalyst from a metal−organic polymer (MOP) by a single-step carbonization process at 500 °C, thus forming a core−shell of iron−nickel-coated carbon (C@ FeNi) nanostructures wired by embedded carbon nanotubes (CNTs) (CNT/C@FeNi). Powder X-ray diffraction confirmed the formation of metallic FeNi 3 alloy nanoparticles (∼20 to 28 nm). Our experimental results showed that MOP containing CNTs acquired an interconnected hierarchical topology, which prevented the collapse of its microstructure during pyrolysis. Hence, CNT/ C@FeNi shows higher porosity (10 times) than C@FeNi. The electrochemical UOR in alkaline electrolytes on these catalysts was studied using cyclic voltammetry (CV). The result showed a higher anodic current (3.5 mA cm −2 ) for CNT/C@FeNi than for C@ FeNi (1.1 mA cm −2 ) at 1.5 V/RHE. CNT/C@FeNi displayed good stability in chronoamperometry experiments and a lower Tafel slope (33 mV dec −1 ) than C@FeNi (41.1 mV dec −1 ). In this study, CNT/C@FeNi exhibits higher exchange current density (3.2 μA cm −2 ) than does C@FeNi (2 μA cm −2 ). The reaction rate orders of CNT/C@FeNi and C@FeNi at a kinetically controlled potential of 1.4 V/RHE were 0.5 and 0.9, respectively, higher than the 0.26 of β-Ni(OH) 2 , Ni/Ni(OH) 2 electrodes. The electrochemical impedance result showed a lower charge-transfer resistance for CNT/C@FeNi (61 Ω•cm −2 ) than for C@FeNi (162 Ω•cm −2 ), due to faster oxidation kinetics associated with the CNT linkage. Moreover, CNT/C@FeNi exhibited a lower Tafel slope and resistance and higher heterogeneity (25.2 × 10 −5 cm s −1 ), as well as relatively high faradic efficiency (68.4%) compared to C@ FeNi (56%). Thus, the carbon-coated FeNi 3 core connected by CNT facilitates lower charge-transfer resistance and reduces the UOR overpotential.

SummaryComparing activities of purified toxins from Bacillus thuringiensis ssp. israelensis against larvae of seven mosquito species (vectors of tropical diseases) that belong to three genera, gleaned from the literature, disclosed highly significant variations in the levels of LC50 as well as in the hierarchy of susceptibilities. Similar toxicity comparisons were performed between nine transgenic Gram-negative species, four of which are cyanobacterial, expressing various combinations of cry genes, cyt1Aa and p20, against larvae of four mosquito species as potential agents for biological control. Reasons for inconsistencies are listed and discussed. Standard conditions for toxin isolation and presentation to larvae are sought. A set of lyophilized powders prepared identically from six Escherichia coli clones expressing combinations of four genes displayed toxicities against larvae of three mosquito species, with levels that differed between them but with identical hierarchy.