title: Mimicking the role of the antenna in photosynthetic photoprotection.
abstract: One mechanism used by plants to protect against damage from excess sunlight is called nonphotochemical quenching (NPQ). Triggered by low pH in the thylakoid lumen, NPQ leads to conversion of excess excitation energy in the antenna system to heat before it can initiate production of harmful chemical species by photosynthetic reaction centers. Here we report a synthetic hexad molecule that functionally mimics the role of the antenna in NPQ. When the hexad is dissolved in an organic solvent, five zinc porphyrin antenna moieties absorb light, exchange excitation energy, and ultimately decay by normal photophysical processes. Their excited-state lifetimes are long enough to permit harvesting of the excitation energy for photoinduced charge separation or other work. However, when acid is added, a pH-sensitive dye moiety is converted to a form that rapidly quenches the first excited singlet states of all five porphyrins, converting the excitation energy to heat and rendering the porphyrins kinetically incompetent to readily perform useful photochemistry.
authors.affiliation: Department of Chemistry and Biochemistry, Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Terazono
authors.forename: Gerdenis
authors.initials: G
authors.lastname: Kodis
authors.forename: Kul
authors.initials: K
authors.lastname: Bhushan
authors.forename: Julia
authors.initials: J
authors.lastname: Zaks
authors.forename: Christopher
authors.initials: C
authors.lastname: Madden
authors.forename: Ana L
authors.initials: AL
authors.lastname: Moore
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Moore
authors.forename: Graham R
authors.initials: GR
authors.lastname: Fleming
authors.forename: Devens
authors.initials: D
authors.lastname: Gust
mesh_terms: D040761:Biomimetic Materials / Q000737:chemistry*; D032701:Biomimetics; D008665:Metalloporphyrins / Q000737:chemistry*; D015394:Molecular Structure; D055668:Photochemical Processes; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D010944:Plants / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D008665:Metalloporphyrins; D045322:Photosynthetic Reaction Center Complex Proteins; C017802:zinc hematoporphyrin