FIGURE 1.

(A) Wobbling-in-a-cone model. The transition dipole moment μ(t) is assumed to freely diffuse inside a cone with the semicone angle θ_max. (B) Cone-in-a-cone model. The two top figures indicate a motion, which is due to the protein flexibility, superimposed to the wobbling-in-a-cone model. The bottom figure visualizes how the protein flexibility is described in the cone-in-a-cone model by the protein cone, within which the dye cone freely diffuses.