Date of Award
Doctor of Philosophy
Gerald J. Small
Walter S. Struve
Low temperature absorption and hole burning spectroscopies were applied to the D1-D2-cyt b[subscript]559, and the CP47 and CP43 antenna protein complexes of Photosystem II from higher plants. Low temperature transient and persistent hole-burning data and theoretical calculations on the kinetics and temperature dependence of the P680 hole profile are presented and provide convincing support for the linker model. Implicit in the linker model is that the 684-nm-absorbing Chl a serve to shuttle energy from the proximal antenna complex to reaction center. The stoichiometry of isolated Photosystem II Reaction Center (PSII RC) in several different preparations is also discussed. The additional Chl a are due to 684-nm-absorbing Chl a, some contamination by the CP47 complex, and non-native Chl a absorbing near 670 nm. In the CP47 protein complex, attention is focused on the lower energy chlorophyll a Q[subscript] y-states. On the basis of the analysis of the hole and static fluorescence spectra at 4.2 K, the lowest energy state of CP47 was found to be at 690 nm. The 690 nm and 687 nm states are excitonically correlated and correspond to an excitonically coupled dimer. High pressure hole-burning studies of PSII RC revealed for the first time a strong pressure effect on the primary electron transfer dynamics. The 4.2 K lifetime of P680*, the primary donor state, increases from 2.0 ps to 7.0 ps as pressure increases from 0.1 to 267 MPa. Importantly, this effect is irreversible (plastic) while the pressure induced effect on the low temperature absorption and non-line narrowed P680 hole spectra are reversible (elastic). Nonadiabatic rate expressions, which take into account the distribution of energy gap values, are used to estimate the linear pressure shift of the acceptor state energy for both the superexchange and two-step mechanisms for primary charge separation. It was found that the pressure dependence could be explained with a linear pressure shift of ≈1 cm[superscript]-1/MPa in magnitude for the acceptor state. The results point to the marriage of hole burning and high pressures as having considerable potential for the study of primary transport dynamics in reaction centers and antenna complexes.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Chang, Hai-Chou, "Spectral hole burning studies of Photosystem II " (1995). Retrospective Theses and Dissertations. 10766.