Effects of detergent on the excited state structure and relaxation dynamics of the photosystem II reaction center: A high resolution hole burning study

Low temperature (4.2 K) absorption and hole burned spectra are reported for a stabilized preparation (no excess detergent) of the photosystem II reaction center complex. The complex was studied in glasses to which detergent had and had not been added. Triton X-100 (but not dodecyl maltoside) detergent was found to significantly affect the absorption and persistent hole spectra and to disrupt energy transfer from the accessory chlorophyll a to the active pheophytin a. However, Triton X-100 does not significantly affect the transient hole spectrum and lifetime (1.9 ps at 4.2 K) of the primary donor state, P680^*. Data are presented which indicate that the disruptive effects of Triton X-100 are not due to extraction of pigments from the reaction center, leaving structural perturbations as the most plausible explanation. In the absence of detergent the high resolution persistent hole spectra yield an energy transfer decay time for the accessory Chl a Q_Y-state at 1.6 K of 12 ps, which is about three orders of magnitude longer than the corresponding time for the bacterial RC. In the presence of Triton X-100 the Chl a Q_Y-state decay time is increased by at least a factor of 50.Abbreviations PS I photosystem I - PS II photosystem II - RC reaction center - P680, P870, P960 the primary electron donor absorption bands of photosystem II, Rhodobacter sphaeroides, Rhodopseudomonas viridis - NPHB nonphotochemical hole burning - TX Triton X-100 - DM Dodecyl Maltoside - Chl chlorophyll - Pheo pheophytin - ZPH ero phonon hole