A novel BioXAS technique with sub-millisecond time resolution to track oxidation state and structural changes at biological metal centers

Oxidation-state and structural changes at the metal center are crucial for the catalytic reactions of most metalloenzymes. The characterization of reaction intermediates is a prerequisite for understanding the catalytic mechanism. Frequently, intermediates are formed on the microsecond to millisecond timescale. To follow these reactions in real time represents a major challenge in structural biology. Time-resolved BioXAS is a particularly promising tool for resolving such intermediates. A novel approach for BioXAS, termed 'sampling-XAS', is presented. First room-temperature sampling-XAS results have been obtained for the manganese complex of oxygenic photosynthesis. Oxidation-state changes are monitored with a time resolution as good as 200 mus. The current prospects and limitations as well as future perspectives of time-resolved BioXAS are discussed.