Spectral distributions of "trap" pigments in the RC, CP47, and CP47-RC complexes of photosystem II at low temperature: A fluorescence line-narrowing and hole-burning study

Broad-band absorption and fluorescence, fluorescence line-narrowing (FLN), and spectral hole-burning experiments have been performed on the Q(y)-band of three subcore reaction-center complexes of photosystem II between 1.2 an d 4.2 K: the isolated reaction center (RC), the inner core antenna CP47, an d the CP47-RC complex. In the RC, fluorescence line-narrowing (FLN) is obse rved for excitation wavelengths lambda(exc) greater than or equal to 676 nm , whereas in CP47, this occurs for lambda(exc) greater than or equal to 680 nm. The FLN spectra of CP47-RC appear to be the sum of the individual spec tra of the RC and CP47, an indication that this complex has two "traps". Th is has been confirmed from the spectral distributions obtained by measuring the hole depth (at constant hole width) as a function of zeta(exc), as pre viously done for the RC [Groot, M. L., et al. J. Phys. Chem. 100, 1996, 114 88]. The maxima of these distributions are at similar to 682 nm for the RC "trap" and at similar to 690 nm for the CP47 "trap" within the CP47-RC comp lex. Further support that the two distributions of pigments in CP47-RC belo ng indeed to "trap" pigments is provided by the "effective" homogeneous lin e width Gamma(hom)' determined as a function of temperature for various exc itation and detection wavelengths.