Development of a biosensor for urea assay based on amidase inhibition, using an ion-selective electrode

A biosensor for urea has been developed based on the observation that urea is a powerful active-site inhibitor of amidase, which catalyzes the hydrolysis of amides such as acetamide to produce ammonia and the corresponding organic acid. Cell-free extract from Pseudomonas aeruginosa was the source of amidase (acylamide hydrolase, EC 3.5.1.4) which was immobilized on a polyethersulfone membrane in the presence of glutaraldehyde; anion-selective electrode for ammonium ions was used for biosensor development. Analysis of variance was used for optimization of the biosensorresponse and showed that 30 mu L of cell-free extract containing 7.47 mg protein mL(-1), 2 mu L of glutaraldehyde (5%, v/v) and 10 mu L of gelatin (15%, w/v) exhibited the highest response. Optimization of other parameters showed that pH 7.2 and 30 min incubation time were optimum for incubation ofmembranes in urea. The biosensor exhibited a linear response in the range of 4.0-10.0 mu M urea, a detection limit of 2.0 mu M for urea, a response timeof 20 s, a sensitivity of 58.245 % per mu M urea and a storage stability of over 4 months. It was successfully used for quantification of urea in samples such as wine and milk; recovery experiments were carried out which revealed an average substrate recovery of 94.9%. The urea analogs hydroxyurea, methylurea and thiourea inhibited amidase activity by about 90%, 10% and 0%, respectively, compared with urea inhibition.

Relatório de projeto Milk Run Software

Em suma este trabalho de projeto visa a criação de uma ferramenta que permita a gestão dos transportes para a recolha de matéria-prima necessária ao bom funcionamento da fábrica de produção automóvel Volkswagen Autoeuropa num ambiente dinâmico, sendo esta desenvolvida para responder às necessidades da empresa. Assim foi desenvolvido o protótipo Milk Run Software que consiste basicamente na integração de informação fornecida pela empresa relativa a consumos de materiais provenientes de ordens de produção, fornecedores e transportes. Com base nestes dados e recurso a sistemas externos é efetuada a georreferenciação de fornecedores para que exista a noção de proximidade entre estes, além disso foi construído um sistema de decisão, para que com base nos consumos (peças, pesos e volumes), se consigam determinar e gerir as rotas de transportes da empresa Volkswagen Autoeuropa com base no conceito Milk Run, que consiste na otimização do transporte de peças para montagem de veículos, no qual tem em conta a localização geográfica, o volume ou peso a transportar, as limitações físicas dos veículos de transporte, bem como o número de paragens máximas (cargas a efetuar no percurso). Neste projeto são utilizadas diversas técnicas de análise protagonizadas para a construção de ferramentas com o recurso à Engenharia de Software, e a algumas técnicas na área de pesquisa em espaços de estado para auxiliar o conceito Milk Run para resolução dos problemas encontrados.

Tuneable micro- and nano-periodic structures in urethane/urea networks

Micro- and nano-patterned materials are of great importance for the design of new nanoscale electronic, optical and mechanical devices, ranging from sensors to displays. A prospective system that can support a designed functionality is elastomeric polyurethane thin films with nano- or micromodulated surface structures ("wrinkles"). These wrinkles can be induced on different lengthscales by mechanically stretching the films, without the need for any sophisticated lithographic techniques. In the present article we focus on the experimental control of the wrinkling process. A simple model for wrinkle formation is also discussed, and some preliminary results reported. Hierarchical assembly of these tunable structures paves the way for the development of a new class of materials with a wide range of applications, from electronics to biomedicine.