Reengineering the optical absorption cross-section of photosynthetic reaction centers

J Am Chem Soc. 2014 Mar 26;136(12):4599-604. doi: 10.1021/ja411843k. Epub 2014 Mar 13.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Absorption
  • Cytochromes c / metabolism
  • Energy Transfer
  • Models, Molecular
  • Optical Phenomena*
  • Oxidation-Reduction
  • Photosynthetic Reaction Center Complex Proteins / chemistry*
  • Photosynthetic Reaction Center Complex Proteins / genetics*
  • Photosynthetic Reaction Center Complex Proteins / metabolism
  • Protein Conformation
  • Protein Engineering / methods*
  • Rhodobacter sphaeroides / enzymology

Substances

  • Photosynthetic Reaction Center Complex Proteins
  • Cytochromes c