RESUMEN
Enhanced chemiluminescence (ECL) describes the phenomenon of increased light output in the luminol oxidation reaction catalysed by horseradish peroxidase (HRP) in the presence of certain compounds, such as para-iodophenol. In this work, the effects of phenol on the para-iodophenol-enhanced HRP-catalysed chemiluninescent reaction intensity in an aqueous buffer (Tris-HCl buffer, pH 8.5) and in a surfactant-water-octane mixture were compared. Preincubation of HRP at low phenol concentrations stimulated the chemiluminescent intensity in the assay performed in an aqueous buffer, but did not have significant effect in the sodium bis(2-ethylhexyl)sulphosuccinate) (Aerosol OT, AOT) applied system. It was also observed that HRP preincubation with phenol concentration higher than 0.003 mg/mL produced an inhibitory effect on the enzyme activity for both assay systems. Only an inhibitory effect of phenol on the chemiluminescent intensity in the surfactant system in octane (as organic solvent) was observed. Three assays were developed to determine phenol concentration in water and in an organic solvent mixture. The detection limits were 0.006, 0.003 and 0.0005 mg/mL, respectively, for the buffer-containing system, the AOT-applied system with phenol standard solutions in water and for the AOT-applied system with phenol standard solutions in octane.
Asunto(s)
Fenoles/análisis , Calibración , Peroxidasa de Rábano Silvestre/química , Peroxidasa de Rábano Silvestre/metabolismo , Cinética , Modelos Lineales , Mediciones Luminiscentes , Luminol/química , Luminol/metabolismo , Octanos/química , Sensibilidad y Especificidad , Tensoactivos/química , Agua/química , Contaminantes Químicos del Agua/análisisRESUMEN
We describe two types of models. In the first one it is assumed that regulation of enzyme activity occurs by the product of the enzyme reaction. In the second it is assumed that concomitant action of ligand occurs on at least two targets with opposite effects (dual-action model). Kinetic analysis of models of the first type shows that homeostatic response with respect to the key metabolite of the receptor-enzyme system is possible only if the enzyme kinetics are described by the equation of zero order. In 'dual-action' models, the homeostatic behavior of the system is defined by the mechanisms of compensation of the ligand primary effect.
Asunto(s)
Enzimas/metabolismo , Homeostasis , Receptores de Superficie Celular/metabolismo , Cinética , Modelos BiológicosRESUMEN
A theoretical kinetic model describing the behavior of a receptor-enzyme system during formation of drug addiction is considered in this article. The model assumes concomitant action of narcotic on at least two targets with opposite effects. Theoretical kinetic principles that the system must satisfy for the development of drug addiction are formulated. These kinetic principles are the slow inactivation of receptor-enzyme system and the divergence of characteristic times of dynamic concentration of product and enzyme.
Asunto(s)
Enzimas/metabolismo , Receptores Opioides/metabolismo , Trastornos Relacionados con Sustancias/metabolismo , Cinética , Modelos Biológicos , Trastornos Relacionados con Sustancias/enzimologíaRESUMEN
We have studied the kinetics of the conservative behavior of systems which are subject to the dual action of an external effector or a negative feedback. Conditions have been found under which the dual-action mechanism produces conservative behavior. Negative feedback alone was shown not to produce the conservative behavior of an enzyme-receptor system.