Steady-state flux ratio analysis: application to biological transport

A thermodynamically constrained method of flux ratio analysis, based upon a previously developed thermodynamic rate ratio equation has been developed. In this paper it is demonstrated that, for a complex reaction, application of the thermodynamic rate ratio equation may provide a useful tool for the interpretation of unidirectional flux data thought to be mediated by the reaction, provided that: (i) a clearly defined mechanism for the reaction has been proposed; (ii) a set of partial reaction components may be defined for the reaction from the proposed mechanism, with the rate ratio of at least one of these components being amenable to experimental measurement. This paper defines the conditions for which the rate ratio of a component reaction may be measured, and illustrates the basic principles underlying this approach to flux ratio analysis by direct application to a number of hypothetical mechanisms for biological transport phenomena.