Expanding Covalent Attachment Sites of Nonnative Chromophores to Encompass the C‐Terminal Hydrophilic Domain in Biohybrid Light‐Harvesting Architectures

Abstract

AbstractIncreasing the solar spectral coverage of native photosynthetic antennas can be achieved using biohybrid light‐harvesting (LH) structures comprised of native‐like bacterial photosynthetic peptides and synthetic bacteriochlorins with strong near‐infrared absorption. Four such biohybrids have been prepared wherein synthetic maleimido‐bearing bacteriochlorin BC1‐mal is covalently attached to a Cys residue substituted at either the +1, +5 or +11 position (relative to His‐0) of the 48‐residue β‐peptide of Rb. sphaeroides LH1. In addition, a β‐peptide with Phe substituted for Tyr at the +4 position along with +1Cys was used to examine possible quenching of the excited BC1 by the Tyr. The β‐peptide analogs, as well as their peptide‐BC1 conjugates when combined with native α‐peptide, and bacteriochlorophyll a (BChl a) self‐assemble to form αβ‐dyads and therefrom LH1‐type cyclic (αβ)n oligomers. Static and time‐resolved optical studies show that all of the oligomeric assemblies transfer excitation energy from the appended BC1 to the BChl a array (B875) with an average efficiency of 85 %.