A highly efficient heptamethine cyanine antenna for photosynthetic Reaction Center: From chemical design to ultrafast energy transfer investigation of the hybrid system

Year: 2019

Authors: la Gatta S., Milano F., Farinola G.M., Agostiano A., Di Donato M., Lapini A., Foggi P., Trotta M., Ragni R.

Autors Affiliation: Univ Bari Aldo Moro, Dipartimento Chim, Via Orabona 4, I-70125 Bari, Italy; CNR, IPCF, Bay Unit, Via Orabona 4, I-70125 Bari, Italy; LENS European Lab Nonlinear Spect, Via N Carrara 1, I-50019 Sesto Fiorentino, FI, Italy; INO, Largo Fermi 6, I-50125 Florence, Italy; Univ Perugia, Dept Chem, Via Elce Sotto 8, I-06100 Perugia, Italy.

Abstract: The photosynthetic Reaction Center (RC) from the purple bacterium Rhodobacter sphaeroides has unique photoconversion capabilities, that can be exploited in assembly biohybrid devices for applications in solar energy conversion. Extending the absorption cross section of isolated RC through covalent functionalization with ad-hoc synthesized artificial antennas is a successful strategy to outperform the efficiency of the pristine photoenzyme under visible light excitation. Here we report a new heptamethine cyanine antenna that, upon covalent binding to RC, forms a biohybrid (hCyN7-RC) which, under white light excitation, has doubled photoconversion efficiency versus the bare photoenzyme. The artificial antenna hCyN7 successfully meets appropriate optical properties, i.e. peak position of absorption and emission maximum in the visible and NIR region respectively, large Stokes shift, and high fluorescence quantum yield, required for improving the efficiency of the biohybrid in the production of the charge-separated state in the RC. The kinetics of energy transfer and charge separation of hCyN7-RC studied via ultrafast visible and IR spectroscopies are here presented. The antenna transfers energy to RC chromophores within <10 ps and the rate of Q(A) reduction is doubled compared to the native RC. These experiments further demonstrate hCyN7-RC, besides being an extremely efficient white light photoconverter, fully retains the charge separation mechanism and integrity of the native RC photoenzyme, thus allowing to envisage its suitability as biohybrid material in bioinspired systems for solar energy conversion. Journal/Review: BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS

Volume: 1860 (4)      Pages from: 350  to: 359

More Information: Massimo Dell´Edera is acknowledged for his help in the synthesis of hCyN7. This work was financed by University degli Studi “Aldo Moro” di Bari, Italy (IDEA 2011 project “BIOEXTEND: Extending enzymatic properties by bioconjugation of enzymes with fluorescent organic oligomers”) and by the Apulia Region, Italy funded (Project “FONTANAPULIA – FOtocatalizzatori NanosTrutturati e rAdiazioNe UV per un?Acqua piu PULItA” Project n. WOBV6K5).
KeyWords: Bioconjugation; Biophotovoltaic; Light harvesting antenna; Photocurrent; Photoenzyme; Photosynthetic bacteria; Solar energy conversion
DOI: 10.1016/j.bbabio.2019.01.009

Citations: 16
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