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- Title
Amphiphilic, hydrophilic, or hydrophobic synthetic bacteriochlorins in biohybrid light-harvesting architectures: consideration of molecular designs.
- Authors
Jiang, Jianbing; Reddy, Kanumuri; Pavan, M.; Lubian, Elisa; Harris, Michelle; Jiao, Jieying; Niedzwiedzki, Dariusz; Kirmaier, Christine; Parkes-Loach, Pamela; Loach, Paul; Bocian, David; Holten, Dewey; Lindsey, Jonathan
- Abstract
Biohybrid light-harvesting architectures can be constructed that employ native-like bacterial photosynthetic antenna peptides as a scaffold to which synthetic chromophores are attached to augment overall spectral coverage. Synthetic bacteriochlorins are attractive to enhance capture of solar radiation in the photon-rich near-infrared spectral region. The effect of the polarity of the bacteriochlorin substituents on the antenna self-assembly process was explored by the preparation of a bacteriochlorin-peptide conjugate using a synthetic amphiphilic bacteriochlorin (B1) to complement prior studies using hydrophilic (B2, four carboxylic acids) or hydrophobic (B3) bacteriochlorins. The amphiphilic bioconjugatable bacteriochlorin B1 with a polar ammonium-terminated tail was synthesized by sequential Pd-mediated reactions of a 3,13-dibromo-5-methoxybacteriochlorin. Each bacteriochlorin bears a maleimido-terminated tether for attachment to a cysteine-containing analog of the Rhodobacter sphaeroides antenna β-peptide to give conjugates β-B1, β-B2, and β-B3. Given the hydrophobic nature of the β-peptide, the polarity of B1 and B2 facilitated purification of the respective conjugate compared to the hydrophobic B3. Bacteriochlorophyll a (BChl a) associates with each conjugate in aqueous micellar media to form a dyad containing two β-peptides, two covalently attached synthetic bacteriochlorins, and a datively bonded BChl- a pair, albeit to a limited extent for β-B2. The reversible assembly/disassembly of dyad (β-B2/BChl) was examined in aqueous detergent (octyl glucoside) solution by temperature variation (15-35 °C). The energy-transfer efficiency from the synthetic bacteriochlorin to the BChl- a dimer was found to be 0.85 for (β-B1/BChl), 0.40 for (β-B2/BChl), and 0.85 for (β-B3/BChl). Thus, in terms of handling, assembly and energy-transfer efficiency taken together, the amphiphilic design examined herein is more attractive than the prior hydrophilic or hydrophobic designs.
- Subjects
BACTERIOCHLORIN; AMPHIPHILES; HYDROPHILIC compounds; HYDROPHOBIC compounds; LIGHT-harvesting complex (Photosynthesis); BIOCONJUGATES
- Publication
Photosynthesis Research, 2014, Vol 122, Issue 2, p187
- ISSN
0166-8595
- Publication type
Article
- DOI
10.1007/s11120-014-0021-9