FLUORESCENCE POLARIZATION OF TRIPLE-CHROMOPHORE COMPLEXES WITH ENERGY-TRANSFER

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(sic12) + q13 cos2(sic 13) + q23 cos2(sic 23) and parameters A and q(ij) are dependent on the kinetic parameters of energy exchange and the chromophore spectroscopic parameters. The angle sic(ij) 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, alpha-84, beta-84, and beta-155. Polarized spectra were calculated for both the emission and the excitation spectra of C-PC beta subunits and monomers.