Experimental design in global compartmental analysis of reversible intramolecular two-state excited-state processes with added quencher

Abstract

Although reversible intramolecular two-state excited-state processes without a priori information are unidentifiable, bounds on the excited-state rate constants k(ij) can be specified when a quencher is used [Van Dommelen et al. J. Phys. Chem. 1993, 97, 11738]. These limits can be obtained by a scanning procedure consisting of a series of global compartmental analyses of a fluorescence decay surface in which one of the rate constants k(ij) is held fixed at different preset values. The theory requires that the rate constants of quenching (k(Q1), k(Q2)) for the two excited species have different values. In the present paper, computer-generated fluorescence decay surfaces are used to investigate the criteria under which reliable estimates of the bounds on the rate constants k(ij) can be obtained. If the values of k(Q1) and k(Q2) are substantially different, reliable estimates are obtained. If k(Q1) and k(Q2) are nearly equal in value, the quality of the estimates of the bounds depends on the combinations of the values of the rate constants k(ij). It may happen that no reliable Limits for the rate constants can be obtained so that another quencher is required. A test procedure based on a limited number of decay traces is described which allows one to assess the appropriateness of the quencher for the given excited-state process.