Abstract
Nonphotochemical quenching (NPQ) of chlorophyll fluorescence plays an important role in the protection of plants against excessive light. Fluorescence quenching of the major light-harvesting complex (LHCII) provides a model system to study the mechanism of NPQ. The existence of both quenched and nonquenched states of LHCII has been postulated. We used time-resolved fluorescence and hydrostatic pressure to study differences between these states. Pressure shifts the thermodynamic equilibrium between the two states. The estimated volume difference was 5 mL/mol, indicating a local conformational switch. The estimated free energy difference was 7.0 kJ/mol: high enough to keep the quenched state population low under normal conditions, but low enough to switch in a controlled way. These properties are physiologically relevant properties, because they guarantee efficient light harvesting, while at the same time maintaining the capacity to switch to a quenched state. These results indicate that conformational changes of LHCII can play an important role in NPQ.
Original language | English |
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Pages (from-to) | 7631-7637 |
Number of pages | 7 |
Journal | The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical |
Volume | 111 |
Issue number | 26 |
DOIs | |
Publication status | Published - 2007 |
Keywords
- nonphotochemical energy-dissipation
- chlorophyll-protein complex
- photosystem-ii
- green plants
- chloroplast membranes
- excitation dynamics
- antenna complex
- molecular-basis
- lhcii
- absorption