Equilibrium between quenched and nonquenched conformations of the major plant light-harvesting complex studied with high-pressure time-resolved fluorescence

Bart van Oort, Arie van Hoek, Alexander V. Ruban, Herbert van Amerongen

Research output: Contribution to JournalArticleAcademicpeer-review

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 languageEnglish
Pages (from-to)7631-7637
Number of pages7
JournalJournal of Physical Chemistry B
Volume111
Issue number26
DOIs
Publication statusPublished - 2007

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