Synthesis of a cofacial chlorin dimer of defined symmetry

2012 ◽  
Vol 16 (05n06) ◽  
pp. 626-632 ◽  
Author(s):  
Nguyen Thi Viet Thanh ◽  
Thorsten Könekamp ◽  
Daniela Hanke ◽  
Franziska Löwer ◽  
Tobias Borrmann ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Reaction Center ◽  
Photosynthetic Reaction Center ◽  
Initial Step ◽  
Reaction Centers ◽  
Photosynthetic Reaction Centers ◽  
Special Pair ◽  
Dimeric Structure ◽  
Rigid Spacer

Special pair chlorophylls arranged in a cofacial dimeric structure play an important role in the initial step of light induced electron transfer of photosynthetic reaction centers of bacteria and plants. For mimicking the natural photosynthetic reaction center we aimed on synthesis of an artificial special pair 13 constructed from two chlorin subunits 5a, b and a rigid biphenylene spacer moiety 11. Due to the reduced C2h symmetry of the chlorin units compared with so far used D4h porphyrins and due to the rigid spacer a cofacial dimer of defined symmetry and distance was obtained.

scholarly journals Highly oriented photosynthetic reaction centers generate a proton gradient in synthetic protocells

2017 ◽  
Vol 114 (15) ◽  
pp. 3837-3842 ◽  
Author(s):  
Emiliano Altamura ◽  
Francesco Milano ◽  
Roberto R. Tangorra ◽  
Massimo Trotta ◽  
Omar Hassan Omar ◽  
...  
Keyword(s):  
Reaction Center ◽  
Lipid Membrane ◽  
Transmembrane Protein ◽  
Photosynthetic Reaction Center ◽  
Lipid Vesicles ◽  
Reaction Centers ◽  
Proton Gradient ◽  
Continuous Illumination ◽  
Photosynthetic Reaction Centers ◽  
Transfer Method

Photosynthesis is responsible for the photochemical conversion of light into the chemical energy that fuels the planet Earth. The photochemical core of this process in all photosynthetic organisms is a transmembrane protein called the reaction center. In purple photosynthetic bacteria a simple version of this photoenzyme catalyzes the reduction of a quinone molecule, accompanied by the uptake of two protons from the cytoplasm. This results in the establishment of a proton concentration gradient across the lipid membrane, which can be ultimately harnessed to synthesize ATP. Herein we show that synthetic protocells, based on giant lipid vesicles embedding an oriented population of reaction centers, are capable of generating a photoinduced proton gradient across the membrane. Under continuous illumination, the protocells generate a gradient of 0.061 pH units per min, equivalent to a proton motive force of 3.6 mV⋅min−1. Remarkably, the facile reconstitution of the photosynthetic reaction center in the artificial lipid membrane, obtained by the droplet transfer method, paves the way for the construction of novel and more functional protocells for synthetic biology.

Mimicking Photosynthetic Electron Transfer

1990 ◽  
Vol 218 ◽  
Author(s):  
Devens Gust ◽  
Thomas A. Moore ◽  
Ana L. Moore
Keyword(s):  
Electron Transfer ◽  
Potential Energy ◽  
Reaction Center ◽  
Chemical Potential ◽  
Reaction Centers ◽  
Photosynthetic Reaction Centers ◽  
Photovoltaic Devices ◽  
Molecular Scale ◽  
Energetic Charge ◽  
Photosynthetic Electron Transfer

AbstractThe photosynthetic reaction centers of plants and bacteria are photovoltaic devices on the molecular scale which convert light energy into chemical potential energy in the form of long-lived, energetic charge separated states. It is now possible to prepare synthetic multicomponent molecules which mimic important aspects of this process. For example, one of the keys to reaction center function is a multistep electron transfer strategy. In this paper, two general types of multistep electron transfer, sequential and parallel, are described and illustrated with several synthetic triad and pentad molecules.

A New Pathway for Transmembrane Electron Transfer in Photosynthetic Reaction Centers ofRhodobacter sphaeroidesNot Involving the Excited Special Pair†

Biochemistry ◽  
1997 ◽  
Vol 36 (23) ◽  
pp. 6855-6861 ◽  
Author(s):  
Marion E. Van Brederode ◽  
Michael R. Jones ◽  
Frank Van Mourik ◽  
Ivo H. M. Van Stokkum ◽  
Rienk Van Grondelle
Keyword(s):  
Electron Transfer ◽  
Reaction Centers ◽  
Photosynthetic Reaction Centers ◽  
Special Pair

scholarly journals Excitonic structure and charge separation in the heliobacterial reaction center probed by multispectral multidimensional spectroscopy

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yin Song ◽  
Riley Sechrist ◽  
Hoang H. Nguyen ◽  
William Johnson ◽  
Darius Abramavicius ◽  
...  
Keyword(s):  
Reaction Center ◽  
Charge Separation ◽  
Electronic Spectroscopy ◽  
Spectroscopic Studies ◽  
Primary Electron ◽  
Reaction Centers ◽  
Separation Mechanism ◽  
Photosynthetic Reaction Centers ◽  
Density Analysis ◽  
Function Relationship

AbstractPhotochemical reaction centers are the engines that drive photosynthesis. The reaction center from heliobacteria (HbRC) has been proposed to most closely resemble the common ancestor of photosynthetic reaction centers, motivating a detailed understanding of its structure-function relationship. The recent elucidation of the HbRC crystal structure motivates advanced spectroscopic studies of its excitonic structure and charge separation mechanism. We perform multispectral two-dimensional electronic spectroscopy of the HbRC and corresponding numerical simulations, resolving the electronic structure and testing and refining recent excitonic models. Through extensive examination of the kinetic data by lifetime density analysis and global target analysis, we reveal that charge separation proceeds via a single pathway in which the distinct A0 chlorophyll a pigment is the primary electron acceptor. In addition, we find strong delocalization of the charge separation intermediate. Our findings have general implications for the understanding of photosynthetic charge separation mechanisms, and how they might be tuned to achieve different functional goals.

Excited states of analogue models of M-bacteriochlorophylls (M = Mg, Zn) in the photosynthetic reaction center: a time-dependent density functional theory study

2002 ◽  
Vol 06 (10) ◽  
pp. 617-625 ◽  
Author(s):  
Yoichi Yamaguchi
Keyword(s):  
Electron Transfer ◽  
Excited States ◽  
Density Functional ◽  
Photosynthetic Reaction Center ◽  
Excited Electron ◽  
Time Dependent ◽  
Analogue Model ◽  
Functional Theory ◽  
Special Pair ◽  
Dependent Density

Using time-dependent density functional theory (TDDFT), the excited states of the analogue model Mg -bacteriochlorophyll b - imidazole ( BChl -Im) dimer (P) for a special pair in the photosynthetic reaction center (RC) of Rhodopseudomonas (Rps.) viridis were examined. The calculated low-lying excited states and optimal geometries are in good agreement with experimental data. The order of the lowest unoccupied molecular orbital (LUMO) energies of P, the monomeric "accessory" BChl -Im (B), and bacteriopheophytin b ( H ) indicates the possibility of the light-induced electron transfer from P to H via B. The Im ligand of B destabilizes Goutermann's four-orbitals of BChl by 0.3-0.4 eV. With no energetic difference in the LUMOs between H and BChl , the Im ligands of P and B play an important role in providing a greater energetic gradient to the LUMOs along with the pathway for the excited-electron transfer in RC, resulting in the reduced reverse electron transfer from H to P (via B). Thus it is expected that the asymmetric Mg -Im interactions will directly affect the pathway of the excited-electron transfer. Using the deformed heterodimer (P') formed by the BChl halves with and without Im as the primary donor model, its cation radical P'+ was calculated as to whether the experimental asymmetric spin-density distribution can reproduce. The excited states of the analogue model Zn - BChl -Im dimer for a special pair in RC of the recently discovered Acidiphilium rubrum were also examined for a comparison with P.

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