title: Reengineering the optical absorption cross-section of photosynthetic reaction centers.
abstract: Engineered cysteine residues near the primary electron donor (P) of the reaction center from the purple photosynthetic bacterium Rhodobacter sphaeroides were covalently conjugated to each of several dye molecules in order to explore the geometric design and spectral requirements for energy transfer between an artificial antenna system and the reaction center. An average of 2.5 fluorescent dye molecules were attached at specific locations near P. The enhanced absorbance cross-section afforded by conjugation of Alexa Fluor 660 dyes resulted in a 2.2-fold increase in the formation of reaction center charge-separated state upon intensity-limited excitation at 650 nm. The effective increase in absorbance cross-section resulting from the conjugation of two other dyes, Alexa Fluor 647 and Alexa Fluor 750, was also investigated. The key parameters that dictate the efficiency of dye-to-reaction center energy transfer and subsequent charge separation were examined using both steady-state and time-resolved fluorescence spectroscopy as well as transient absorbance spectroscopy techniques. An understanding of these parameters is an important first step toward developing more complex model light-harvesting systems integrated with reaction centers.
authors.affiliation: Department of Chemistry and Biochemistry and ‡The Biodesign Institute, Arizona State University , Tempe, Arizona 85287, United States.
authors.forename: Palash K
authors.initials: PK
authors.lastname: Dutta
authors.forename: Su
authors.initials: S
authors.lastname: Lin
authors.forename: Andrey
authors.initials: A
authors.lastname: Loskutov
authors.forename: Symon
authors.initials: S
authors.lastname: Levenberg
authors.forename: Daniel
authors.initials: D
authors.lastname: Jun
authors.forename: Rafael
authors.initials: R
authors.lastname: Saer
authors.forename: J Thomas
authors.initials: JT
authors.lastname: Beatty
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: Hao
authors.initials: H
authors.lastname: Yan
authors.forename: Neal W
authors.initials: NW
authors.lastname: Woodbury
mesh_terms: D000042:Absorption; D045304:Cytochromes c / Q000378:metabolism; D004735:Energy Transfer; D008958:Models, Molecular; D055620:Optical Phenomena; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D011487:Protein Conformation; D015202:Protein Engineering / Q000379:methods*; D012242:Rhodobacter sphaeroides / Q000201:enzymology
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D045304:Cytochromes c