A kinetic study of analyte–receptor binding and dissociation for biosensor applications: a fractal analysis for cholera toxin and peptide–protein interactions

A fractal analysis is presented for (a) analyte–receptor binding and (b) binding and dissociation kinetics for biosensor applications. Examples analyzed include the binding of different concentrations of cholera toxin (CT) in solution to fluorophore-labeled ganglioside GM1 immobilized on a biomimetic membrane surface [16], and tyrosine kinase lck SH2 domain in solution to a phosphorylated peptide immobilized on a new cuvette-based surface plasmon resonance (SPR) instrument [14]. A single and a dual-fractal analysis is required to describe the binding kinetics for CT. The dual-fractal analysis represents a change in the binding mechanism as the reaction progresses on the surface. A single and a dual-fractal analysis is required to describe the binding kinetics for tyrosine kinase lck SH2 domain in solution to the phosphorylated peptide. In this case, the dissociation kinetics may be described by a single-fractal analysis. Relationships are presented for the dissociation rate coefficient as a function of (a) the fractal dimension, Dfd or the degree of heterogeneity that exists on the surface, and (b) as a function of the phosphotyrosine peptide, EPQY∗EEIPIYL concentration. When analyte–receptor dissociation is involved, an increase in the heterogeneity on the surface (increase in Dfd) leads to an increase in the dissociation rate coefficient.