Palette of lipophilic bioconjugatable bacteriochlorins for construction of biohybrid light-harvesting architectures

Kanumuri Ramesh Reddy, Jianbing Jiang, Michael Krayer, Michelle A. Harris, Joseph W. Springer, Eunkyung Yang, Jieying Jiao, Dariusz M. Niedzwiedzki, Dinesh Pandithavidana, Pamela S. Parkes-Loach, Christine Kirmaier, Paul A. Loach*, David F. Bocian, Dewey Holten, Jonathan S. Lindsey

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

The challenge of creating both pigment building blocks and scaffolding to organize a large number of such pigments has long constituted a central impediment to the construction of artificial light-harvesting architectures. Light-harvesting (LH) antennas in photosynthetic bacteria are formed in a two-tiered self-assembly process wherein (1) a peptide dyad containing two bacteriochlorophyll a molecules forms, and (2) the dyads associate to form cyclic oligomers composed of 8 or 9 dyads in LH2 and 15 or 16 in LH1 of purple photosynthetic bacteria. While such antenna systems generally have near-quantitative transfer of excitation energy among pigments, only a fraction of the solar spectrum is typically absorbed. A platform architecture for study of light-harvesting phenomena has been developed that employs native photosynthetic peptide analogs, native bacteriochlorophyll a, and synthetic near-infrared-absorbing bacteriochlorins. Herein, the syntheses of 10 lipophilic bacteriochlorins are reported, of which 7 contain bioconjugatable handles (maleimide, iodoacetamide, formyl, carboxylic acid) for attachment to the peptide chassis. The bioconjugatable bacteriochlorins typically exhibit a long-wavelength absorption band in the range 710 to 820 nm, fluorescence yield of 0.1-0.2, and lifetime of the lowest singlet excited state of 2-5 ns. The α-helical structure of the native-like peptide is retained upon conjugation with a synthetic bacteriochlorin, as judged by single-reflection infrared studies. Static and time-resolved optical studies of the oligomeric biohybrid architectures in aqueous detergent solution reveal efficient (∼90%) excitation energy transfer from the attached bacteriochlorin to the native-like bacteriochlorophyll a sites. The biohybrid light-harvesting architectures thus exploit the self-constituting features of the natural systems yet enable versatile incorporation of members from a palette of synthetic chromophores, thereby opening the door to a wide variety of studies in artificial photosynthesis.

Original languageEnglish (US)
Pages (from-to)2036-2053
Number of pages18
JournalChemical Science
Volume4
Issue number5
DOIs
StatePublished - Apr 2 2013

ASJC Scopus subject areas

  • Chemistry(all)

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