Quantitative calculations of fluorescence polarization and absorption anisotropy kinetics of double- and triple-chromophore complexes with energy transfer

Abstract

A new method is presented for calculation of the fluorescence depolarization and kinetics of absorption anisotropy for molecular complexes with a limited number of chromophores. The method considers absorption and emission of light by both chromophores, and also energy transfer between them, with regard to their mutual orientations. The chromophores in each individual complex are rigidly positioned. The complexes are randomly distributed and oriented in space, and there is no energy transfer between them. The new "practical" formula for absorption anisotropy and fluorescence depolarization kinetics, P(t) = [3B(t) - 1 + 2A(t)]/[3 + B(t) + 4A(t)], is derived both for double- and triple-chromophore complexes with delta-pulse excitation. The parameter B(t) is given by (a) B(t) = cos2(theta) for double-chromophore complexes, and (b) B(t) = q12(t)cos2(theta 12) + q13(t)-cos2(theta 13) + q23(t)cos2(theta 23) for triple-chromophore complexes, where q12(t) + q13(t) + q23(t) = 1. Here theta ij are the angles between the chromophore transition dipole moments in the individual molecular complex. The parameters qij(t) and A(t) are dependent on chromophore spectroscopic features and on the rates of energy transfer.

Theory of polarized fluorescence and absorption in molecular complexes comprising two chromophores with non-parallel absorption and emission transition dipole moments

“…Recent results from the femtosecond laser spectroscopy of molecular pairs has stimulated new theoretical investigations of the role of coherence in such polarization phenomena [8][9][10]. However, the background for a theory applicable to incoherent energy transfer in complexes with the spectral characteristics cited in the previous paragraph has only recently been established [11][12][13][14][15]. In our work we continue the theoretical development by eliminating certain limitations that previously applied.…”

Spectroscopic study of the light-harvesting protein C-phycocyanin associated with colorless linker peptides

“…35,36 Atomic resolution and refinement of the structure of PC43sa was quickly followed by other biliprotein structures: PECp5"6 PE,37,41947 APC4* and most recently APC associated with its …”