title: Artificial Photosynthetic Reaction Center Exhibiting Acid-Responsive Regulation of Photoinduced Charge Separation.
abstract: Nonphotochemical quenching (NPQ) is a photoprotective regulatory mechanism employed by many photosynthetic organisms to dynamically modulate energy flow within the photosynthetic apparatus in response to fluctuating light conditions. Activated by decreases in lumen pH produced during periods of high photon flux, NPQ induces rapid thermal dissipation of excess excitation energy. As a result, the rate of charge separation (CS) decreases, thereby limiting the accumulation of potentially deleterious reactive intermediates and byproducts. Herein, a molecular triad that functionally mimics the effects of NPQ associated with an artificial photosynthetic reaction center is described. Steady-state absorption and emission, time-resolved fluorescence, and transient absorption spectroscopies have been used to demonstrate a 1 order of magnitude reduction in the CS quantum yield via reversible protonation of an excited-state-quenching molecular switch moiety. As in the natural system, the populations of unquenched and quenched states and therefore the overall yields of CS were found to be dependent on acid concentration.
authors.affiliation: School of Molecular Sciences, Arizona State University , Tempe, Arizona 85287, United States.
authors.forename: Ian
authors.initials: I
authors.lastname: Pahk
authors.affiliation: School of Molecular Sciences, Arizona State University , Tempe, Arizona 85287, United States.
authors.forename: Gerdenis
authors.initials: G
authors.lastname: Kodis
authors.affiliation: Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory and Department of Chemistry and QB3 Institute, University of California , Berkeley, California 94720, United States.
authors.forename: Graham R
authors.initials: GR
authors.lastname: Fleming
authors.affiliation: School of Molecular Sciences, Arizona State University , Tempe, Arizona 85287, United States.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Moore
authors.affiliation: School of Molecular Sciences, Arizona State University , Tempe, Arizona 85287, United States.
authors.forename: Ana L
authors.initials: AL
authors.lastname: Moore
authors.affiliation: School of Molecular Sciences, Arizona State University , Tempe, Arizona 85287, United States.
authors.forename: Devens
authors.initials: D
authors.lastname: Gust