Phase diagram of two fluorescence lifetime components.

Interdependence of two fluorescence lifetime components τ1 and τ2 of wild-type BCA II (■ WT) and its two mutant forms ( L139A and A53C-A76C). Each point was obtained by fitting fluorescence decay curves of protein solution at definite urea concentration. Thick color lines show the “unfolding pathway” for each protein with increase in urea concentration from 0 to 7.5 M. The relative deviations for τ1 and τ2 were ≤3% and ≤7% correspondingly.