A Pseudomonas aeruginosa é um microrganismo comumente presente em efluentes de origem hospitalar, pois é um patógeno nosocomial, causador de infecções de difícil tratamento. A prata possui propriedades antimicrobianas conhecidas, sendo empregada juntamente com carvão ativado em filtros domésticos. Foram portanto, desenvolvidos filtros com amostras de carvão ativado de casca de coco de dendê (Elaeis guineensis) impregnadas com prata, que posteriormente filtraram soluções contendo o microrganismo de estudo. Após incubação, as colônias foram contadas e determinadas (UFC/mL), revelando que a amostra com maior concentração do metal melhor inibiu o crescimento da bactéria, apresentando atividade bacteriostática, e confirmando seu papel fundamental.

Urease is an enzyme containing a dinuclear nickel active center responsible for the hydrolysis of urea into carbon dioxide and ammonia. Interestingly, inorganic models of urease are unable to mimic its mechanism despite their similarities to the enzyme active site. The reason behind the discrepancy in urea decomposition mechanisms between inorganic models and urease is still unknown. To evaluate this factor, we synthesized two bis-nickel complexes, [Ni2L(OAc)] (1) and [Ni2L(Cl)(Et3N)2] (2), based on the Trost bis-Pro-Phenol ligand (L) and encompassing different ligand labilities with coordination geometries similar to the active site of jack bean urease. Both mimetic complexes produced ammonia from urea, (1) and (2), were ten- and four-fold slower than urease, respectively. The presence and importance of several reaction intermediates were evaluated both experimentally and theoretically, indicating the aquo intermediate as a key intermediate, coordinating urea in an outer-sphere manner. Both complexes produced isocyanate, revealing an activated water molecule acting as a base. In addition, the reaction with different substrates indicated the biomimetic complexes were able to hydrolyze isocyanate. Thus, our results indicate that the formation of an outer-sphere complex in the urease analogues might be the reason urease performs a different mechanism.

Urease enzyme has a dinuclear nickel active centre that hydrolyze urea into carbon dioxide and ammonia. In this work, two bis-nickel urease models were synthesized, [Ni₂L(OAc)] and [Ni₂L(Cl)(Et₃N)₂], based on the Trost bis-Pro0Phenol ligand (L). Interestingly, both complexes produced ammonia from urea, in which the [Ni₂L(OAc)] complex was ten times slower than urease, whereas the more labile complex [Ni₂L(Cl)(Et₃N)₂],was only four times slower. The intermediates were evaluated both experimentally and theoretically, indicating that the [Ni₂L(H₂O)₂]⁺ intermediate is the most important to activate urea via an outersphere mechanism. Isocyanate was produced in a self-elimination mechanism. The reaction performed with different substrates indicated that the biomimetic complexes were able to hydrolyze isocyanate. The outersphere activation of urea by these complexes reals an alternative activation mechanism to be considered for the urease enzyme, not yet reported in the literature. . <br>

Urease enzyme has a dinuclear nickel active centre that hydrolyze urea into carbon dioxide and ammonia. In this work, two bis-nickel urease models were synthesized, [Ni₂L(OAc)] and [Ni₂L(Cl)(Et₃N)₂], based on the Trost bis-Pro0Phenol ligand (L). Interestingly, both complexes produced ammonia from urea, in which the [Ni₂L(OAc)] complex was ten times slower than urease, whereas the more labile complex [Ni₂L(Cl)(Et₃N)₂],was only four times slower. The intermediates were evaluated both experimentally and theoretically, indicating that the [Ni₂L(H₂O)₂]⁺ intermediate is the most important to activate urea via an outersphere mechanism. Isocyanate was produced in a self-elimination mechanism. The reaction performed with different substrates indicated that the biomimetic complexes were able to hydrolyze isocyanate. The outersphere activation of urea by these complexes reals an alternative activation mechanism to be considered for the urease enzyme, not yet reported in the literature. . <br>