Modelling of Amperometric Biosensor Used for Synergistic Substrates Determination

In this paper the operation of an amperometric biosensor producing a chemically amplified signal is modelled numerically. The chemical amplification is achieved by using synergistic substrates. The model is based on non-stationary reaction-diffusion equations. The model involves three layers (compartments): a layer of enzyme solution entrapped on the electrode surface, a dialysis membrane covering the enzyme layer and an outer diffusion layer which is modelled by the Nernst approach. The equation system is solved numerically by using the finite difference technique. The biosensor response and sensitivity are investigated by altering the model parameters influencing the enzyme kinetics as well as the mass transport by diffusion. The biosensor action was analyzed with a special emphasis to the effect of the chemical amplification. The simulation results qualitatively explain and confirm the experimentally observed effect of the synergistic substrates conversion on the biosensor response

Modeling Enzymes Inhibition During Microparticles Formation

A mathematical model of enzymes inhibition during microparticles formation has been developed. The model is based on radial substrate diffusion through diffusion layer that surrounds microparticle. The inhibition of enzymes was explained by enzyme adsorption on surface of the microparticles and substrate diffusion limitation through the diffusion layer. The diffusion module is dependent on dimensions of the microparticle. The microparticles with diameter 2 µm may ensure 50% of an apparent activity decrease if half of peroxidase has been adsorbed. Further adsorption of peroxidase and aggregation of the microparticles increases the apparent inhibition

Modeling Enzymes Inhibition During Microparticles Formation

A mathematical model of enzymes inhibition during microparticles formation has been developed. The model is based on radial substrate diffusion through diffusion layer that surrounds microparticle. The inhibition of enzymes was explained by enzyme adsorption on surface of the microparticles and substrate diffusion limitation through the diffusion layer. The diffusion module is dependent on dimensions of the microparticle. The microparticles with diameter 2 µm may ensure 50% of an apparent activity decrease if half of peroxidase has been adsorbed. Further adsorption of peroxidase and aggregation of the microparticles increases the apparent inhibition

Biosensor Response at Mixed Enzyme Kinetics and External Diffusion Limitation in Case of Substrate Inhibition

The action of a biosensor containing non Michaelis-Menten enzyme was modeled at mixed enzyme kinetics and external diffusion limitation in the case of substrate inhibition. The calculations show that at the electrode surface multi steady-state concentrations of substrate may be generated if diffusion module is much larger than 1 and the substrate bulk concentration is much bigger than Michaelis-Menten parameter. The multi steady-state concentration generates multi response of the biosensor. The production of the multi steadystate may cause the biosensor response oscillation

Kinetics of Biocatalytical Synergistic Reactions

Kinetics of biocatalytical synergistic reactions has been analyzed at non-stationary state (NSS) and at quasi steady state (QSS) conditions. The application to the model kinetic constants taken from the first type of the experiments shows that QSS can be established for the enzyme and the mediator at time less than 1 s. Therefore, the analytical solution of the initial rate (IR) may be produced at relevant to an experiment time, and the dependence of the IR on substrates concentration may be analyzed rather easy. The use of kinetic constants from the second type of reactions shows that QSS is formed for the enzyme but not for the mediator. For this reason the modeling of the synergistic process was performed by solving the ordinary differential equations (ODE). For this purpose the novel program KinFitSim (c) was used

Modeling Trienzyme Biosensor at Internal Diffusion Limitation

A model of biosensor containing three immobilized enzymes utilizing consecutive substrate conversion in the chain was developed. The modeling was performed at an internal diffusion limitation and a steadystate condition. The calculations showed that significant response of biosensors was produced if diffusion modules were larger than 1 for all enzyme reactions. Due to diffusion limitation the apparent stability of biosensor response increased many times in comparison to stability of the most labile enzyme of the chain

Productivity and the structure of employment

The paper examines the structure of employment defined by industry, skill, age, part-time and casual employment status and the distribution of earnings. Employment patterns, and changes in employment profiles, are examined for differences between high productivity growth industry sectors and low productivity growth industry sectors.productivity - employment - labour - workforce - education - occupation - unemployment - skills