RESUMO
ABSTRACT: Recalcitrant and intermediate seeds have limitations regarding conservation because of their sensitivity to desiccation and response to storage. Establishing a method for seed storage is difficult because these seeds deteriorate rapidly, which can intensify production of reactive oxygen species that cause lethal oxidative damage to plant tissues. Orthodox seeds, which have greater tolerance to desiccation and storage, are also subject to deterioration processes, in degrees that vary according to the species. Damage caused by harmful levels of free radicals can be mitigated by the action of endogenous or exogenous antioxidants. Recent studies have led to new technologies for protection coming from antioxidants, one of which is cathodic protection. This is a technique with promising results in recalcitrant species, as well as in other living organisms. This paper reviews results regarding the antioxidant activity of cathodic water produced from electrolysis of a calcium chloride and magnesium chloride solution.
RESUMO: As sementes recalcitrantes e intermediárias apresentam limitações com relação à conservação, devido a sua sensibilidade à dessecação e ao comportamento durante o armazenamento. Uma dificuldade no estabelecimento de metodologias para o armazenamento dessas sementes é devido à rápida deterioração, em que atuam processos que podem potencializar a produção de espécies reativas de oxigênio, causando danos oxidativos letais aos tecidos vegetais. Sementes ortodoxas, as quais apresentam maior tolerância à dessecação e ao armazenamento, também sofrem a ação dos processos deteriorativos, em graus variáveis com as espécies. Os danos causados por níveis nocivos de radicais livres podem ser amenizados pela ação de antioxidantes endógenos ou exógenos. Resultados de pesquisas recentes têm possibilitado novas tecnologias de proteção antioxidativa, sendo a proteção catódica uma técnica promissora e com resultados relevantes em espécies sensíveis à dessecação e em outros organismos vivos. Neste trabalho é apresentada uma revisão sobre a ação antioxidante da água catódica, produzida a partir da eletrólise de uma solução contendo cloreto de cálcio e cloreto de magnésio.
RESUMO
The kinetic behavior of the enzyme laccase in solution and immobilized onto carbon platforms using poly(amido amine) (PAMAM) dendrimers has been investigated. The results with the immobilized enzymes have demonstrated that almost ten times more enzyme on the carbon support is required for satisfactory kinetic rates to be achieved. Furthermore, the study as a function of the substrate concentration revealed that the kinetic behavior of the enzyme in solution fits the Michaelis-Menten model. However, when the enzyme is immobilized onto the carbon surface, the catalyzed reaction follows a particular kinetic behavior with apparent positive cooperativity. The highest activity with laccase (in solution or immobilized) is achieved around pH 4.5, and the substrate conversion rate clearly diminishes with rising pH. The optimum temperature lies around 60 °C. The enzyme displays good catalytic activity in a wide range of pH and temperature values. The stability tests evidenced that there is no appreciable reduction in the enzymatic activity after immobilization within the first 30 days. Taking into account both the kinetic and stability tests, one can infer that the use of PAMAM dendrimers seems to be a very attractive approach for the immobilization of enzymes, as well as a feasible and useful methodology for the anchoring of enzymes with potential application in many biotechnological areas.
