First steps towards time-resolved BioXAS at room temperature: state transitions of the manganese complex of oxygenic photosynthesis.

Structural changes and redox transitions at the metal atoms of the active site are essential for the understanding of the catalytic mechanisms of biological metalloenzymes. First steps towards studying these processes by time-resolved X-ray absorption spectroscopy on protein samples (BioXAS) are reported. Photosystem II (PSII) catalyses the light-driven oxidation of bound water molecules at a tetranuclear manganese complex yielding the molecular oxygen of the atmosphere. In this work, first time-resolved XAS results under quasi-physiological conditions (at room temperature, non-crystalline samples) on PSII are presented. Perspectives of time-resolved BioXAS are discussed.