A New Interpretation of the Absorption and the Dual Fluorescence of Prodan in Solution

Prodan is a fluorescent probe used to monitor biological systems such as lipid membrane,proteins and DNA. Remarkable interest is associated to the interpretation of its fluorescent spectrum.In this paper the sequential hybrid Quantum Mechanics/Molecular Mechanics (S-QM/MM) method was used to establish that the fluorescent emission occurs from two different excited states, resulting in a broad asymmetric emission spectrum with two transitions. The absorption spectra in several solvents were measured and calculated using different theoretical models and they all agree that the first observed band is composed of three electronic excitation very close energetically to each other.