Abstract
The formula for the determination of a fluorescence polarization degree is derived for triple-chromophore complexes with energy transfer: P = (3B − 1 + 2A)/(3 + B + 4A). In this formula B = q12 cos2(ϑ12) + q13 cos2(ϑ13) + q23 cos2(ϑ23) and parameters A and qij are dependent on the kinetic parameters of energy exchange and the chromophore spectroscopic parameters. The angle ϑij is the angle between the transition dipole moments of the i and j chromophores. The formula was tested for the particular case of the C-phycocyanin (C-PC) of the blue-green algae Agmenellum quadruplicatum, which contain three chromophores, α-84, β-84, and β-155. Polarized spectra were calculated for both the emission and the excitation spectra of C-PC β subunits and monomers.