New Interpretation of the Hill Coefficient
I. A. Lavrinenko, G. A. Vashanov, Yu. D. Nechipurenko
Abstract
A modification is proposed for the Hill equation, which describes the cooperative binding of a ligand by a macromolecule. A relative coefficient of cooperativity was introduced as a new parameter in the equation to ensure the conjugation of the Hill coefficient with the number of interacting subunits in the oligomer. This makes it possible to clarify the physical meaning of the Hill coefficient and explains the nature of its non-integer values. Normalization of the relative coefficient of cooperativity additionally provides the opportunity to compare the coefficient values for oligomers with different numbers of protomers. The relative coefficient of cooperativity may be useful in solving a wide range of problems where coordinated interactions of elements are described at all levels of the spatial organization of proteins, nucleic acids, their complexes, and receptors with their mediators.