Mathematical analysis for impedance change with proteolytic digestion of gelatin

A mathematical analysis is proposed to demonstrate an inter-relationship between the proteolytic digestion of gelatin on the surface of an interdigitated gold electrode and the resulting rate of impedance change, at different collagenase concentrations, in a biosensor used to detect protease in solution. The impedance change due to digestion of the gelatin layer by collagenase for the overall digestion process was expressed in two different stages: an initial exponential period where the rate of impedance change with enzymic digestion was slow, leading to a critical thickness; after which there was a greater change in impedance associated with subsequent dissolution of the layer and partial or complete uncoating of the digits on the electrode surface. An inter-relationship between the rate of impedance change and collagenase concentration within the range 0.2-0.6 mg ml-1 was predicted for the early stages of the digestion process. A kinetic theory for the rapid rate of impedance change with collagenase concentrations could not be developed owing to the rate remaining almost constant for all concentrations of collagenase, after the critical thickness had been reached. An inter-relationship between the rate of impedance change and stirrer speed was also demonstrated.     

Effect of the local environment and state of the immobilized ligand on its reaction with a macromolecular receptor

We consider a simple statistical model for interaction between a macromolecular receptor and a surface functionalized with low molecular weight ligands of the same type. For the example of the reaction between immobilized sulfamethoxazole and a selective antibody, we have used surface plasmon resonance to demonstrate that the proposed approach is appropriate for describing the dependence of the adsorption capacity on the surface density of the immobilized ligand and its charge state. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 4, pp. 210–216, July–August, 2006.     

Radial basis neural network for the classification of fresh edible oils using an electronic nose

An electronic nose utilising an array of six-bulk acoustic wave polymer coated Piezoelectric Quartz (PZQ) sensors has been developed. The nose was presented with 346 samples of fresh edible oil headspace volatiles, generated at 45°C. Extra virgin olive (EVO), Non-virgin olive oil (OI) and Sunflower oil (SFO), were used over a period of 30 days. The sensor responses were then analysed producing an architecture for the Radial Basis Function Artificial Neural Network (RBF). It was found that the RBF results were excellent, giving classifications of above 99% for the vegetable oil test samples.This revised version was published online in November 2005 with corrections to the Cover Date.     

Interface functional architecture using mixed thiol monolayers: Effect of the composition and spatial organization on the immobilization of low-molecular-weight ligands

A simple procedure is examined for forming a selective sensor coating using mixed self-assembling thiol monolayers functionalized by molecules of the sulfanilamide antibiotic, sulfamethoxazol (SMX). A model is proposed for the interface processes, which accounts for the complex dependence of the adsorption capacity of the coatings obtained on the surface density of the reactive groups and the low adsorption capacity at high reaction site concentrations. The model was supported by competitive inhibition analysis. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 3, pp. 158–164, May–June, 2008.     

The numerical integration of relative equilibrium solutions. The nonlinear Schrodinger equation

We analyse different error propagation mechanisms for conservativeand nonconservative time-integrators of nonlinear Schrödingerequations. We use a geometric approach based on interpretingwaves as relative equilibria.