Mn-porphyrins in a four-helix bundle participate in photo-induced electron transfer with a bacterial reaction center.

Autor: Williams JC; School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA., Faillace MS; School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA., Gonzalez EJ; School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA., Dominguez RE; School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA., Knappenberger K; School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA., Heredia DA; School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA., Moore TA; School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA., Moore AL; School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA., Allen JP; School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA. jallen@asu.edu.
Jazyk: angličtina
Zdroj: Photosynthesis research [Photosynth Res] 2023 Nov 01. Date of Electronic Publication: 2023 Nov 01.
DOI: 10.1007/s11120-023-01051-9
Abstrakt: Hybrid complexes incorporating synthetic Mn-porphyrins into an artificial four-helix bundle domain of bacterial reaction centers created a system to investigate new electron transfer pathways. The reactions were initiated by illumination of the bacterial reaction centers, whose primary photochemistry involves electron transfer from the bacteriochlorophyll dimer through a series of electron acceptors to the quinone electron acceptors. Porphyrins with diphenyl, dimesityl, or fluorinated substituents were synthesized containing either Mn or Zn. Electrochemical measurements revealed potentials for Mn(III)/Mn(II) transitions that are ~ 0.4 V higher for the fluorinated Mn-porphyrins than the diphenyl and dimesityl Mn-porphyrins. The synthetic porphyrins were introduced into the proteins by binding to a four-helix bundle domain that was genetically fused to the reaction center. Light excitation of the bacteriochlorophyll dimer of the reaction center resulted in new derivative signals, in the 400 to 450 nm region of light-minus-dark spectra, that are consistent with oxidation of the fluorinated Mn(II) porphyrins and reduction of the diphenyl and dimesityl Mn(III) porphyrins. These features recovered in the dark and were not observed in the Zn(II) porphyrins. The amplitudes of the signals were dependent upon the oxidation/reduction midpoint potentials of the bacteriochlorophyll dimer. These results are interpreted as photo-induced charge-separation processes resulting in redox changes of the Mn-porphyrins, demonstrating the utility of the hybrid artificial reaction center system to establish design guidelines for novel electron transfer reactions.
(© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)
Databáze: MEDLINE
Externí odkaz: