Identifiability of models for fluorescence quenching in aqueous micellar systems

The first deterministic identifiability analysis is presented for four commonly used kinetic models of fluorescence quenching of an excited probe in aqueous micelles: A) model with immobile quenchers, B) model with mobile quenchers, C) an extension of model B in which exchange of quenchers both via the aqueous phase and during micelle collisions is taken into account, and D) model with probe migration. It is shown that these specific models for fluorescence decay of an excited probe solubilized in a micelle and quenched by molecules or ions that are Poisson-distributed over the micelles, resulting in the generalized four-parameter equation f(t)=A(1) exp{-A(2)t-A(3)[1-A(4)t]}, are uniquely identifiable in terms of four descriptive A parameters. Moreover, each model also can be uniquely identified in terms of the underlying rate constants and micellar concentration or mean micellar aggregation number. This means that these parameters can be extracted in a unique way from time-resolved fluorescence quenching experiments on a probe in micelles. For each model the recommended analysis approach is given.