We have several interconnected interests in the study of photosystem II. These include:
Mechanism of PSII-cyclic electron flow. PSII-CEF is a little-understood process which takes electrons from the QB site and returns them to P680. Our past work has shown this process to occur via at least two pathways, including a PSII-internal and a PSII-external route, but the exact path taken by electrons remains unknown. We are currently probing the routes and regulatory mechanisms involved in PSII-CEF, as well as its distribution across the tree of life.
Mechanism of proton removal from the WOC of PSII. The protons generated during oxidation of water at PSII must be continuously removed to allow the water oxidation cycle to continue. Several mechanisms of proton removal have been proposed; our past experimental work heavily implicates chloride as at least a kinetic regulator. We are currently investigating the routes of the proton removal pathway(s) and the kinetic regulations thereof.
Roles of inorganic cofactors of PSII. PSII contains various inorganic cofactors which are critical to electron transfer processes. We seek to elucidate the roles of these cofactors by inorganic substitution and tuning the local protein environment, taking advantage of our advanced fluorometric and spectroscopic toolkit. Subjects of study include Mn>Co substitution in the WOC, Sr>Ca in the WOC, the non-heme iron between the Q sites, and the three or more bicarbonate functions.
Fluorometric observation of WOC S-states. Oxidation states of the WOC are traditionally observed by inaccessible and costly methods such as EPR, MIMS, and high-sensitivity oximetry. We aim to bring direct observation of the S-state populations, lifetimes, and advance kinetics to anyone with a Joliot-type spectrometer.
We have a longstanding interest in the biogenesis, spatial organization, and repair of the thylakoid membrane. Our studies in this arena include:
Aggregation kinetics of the Vipp1 protein. We are investigating how Vipp1 is recruited to repair membrane damage and what can regulate this mechanism, as well as the roles of Vipp1 in generating specific membrane domains. Our work spans prokaryotic and eukaryotic systems (Synechococcus sp. PCC 7002 and Chlamydomonas reinhardtii, respectively).
Real-time cellular and subcellular domain monitoring. We are developing means of systematically obtaining fluorometric observations of photosynthetic health from as small of a sample as possible in vivo.
Facultative autotrophs and mixotrophs can survive under considerably different metabolic conditions depending on outside environmental factors. We are actively studying the conditions that trigger these trophic mode switches and what exactly the organism does at the cell scale, particularly the photosynthetic electron transport chain.