The light-harvesting antenna of photosystem II (PSII) has the ability to switch rapidly between a state of efficient light utilization and one in which excess excitation energy is harmlessly dissipated as heat, a process known as qE. We have investigated the single-molecule fluorescence intermittency of the main component of the PSII antenna (LHCII) under conditions that mimic efficient utilization of light or qE, and demonstrate that weakly fluorescing states are stabilized under qE conditions. Thus, qE is explained by biological control over the intrinsic dynamic disorder in the complex � the frequencies of switching establish whether the population of complexes is unquenched or quenched. Furthermore, the quenched states were accompanied by two distinct spectral signatures, suggesting more than one mechanism for energy dissipation in LHCII.

Controlled disorder in plant light harvesting complex II explains its photoprotective role

243rd National Meeting (2012)

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