scholarly journals Activity of photosynthetic Reaction Centers coated with polydopamine

MRS Advances ◽  
2020 ◽  
Vol 5 (45) ◽  
pp. 2299-2307
Author(s):  
Francesco Milano ◽  
Marco Lopresti ◽  
Danilo Vona ◽  
Gabrielle Buscemi ◽  
Mariangela Cantore ◽  
...  
Keyword(s):  
Protein Complex ◽  
Complex Function ◽  
Photosynthetic Reaction Center ◽  
Reaction Centers ◽  
Photosynthetic Reaction Centers ◽  
Alkaline Ph ◽  
Colloidal Form ◽  
Insoluble Material ◽  
Dilute Aqueous Solutions ◽  
Pigment Protein Complex

Dilute aqueous solutions of dopamine buffered to an alkaline pH and in the presence of dissolved oxygen undergo to a series of autoxidation and rearrangement reactions that lead to the formation of a dark insoluble material called polydopamine (PDA) with melanin reminiscent properties. In this work we carried out this reaction in the presence of the photosynthetic reaction center (RC), a transmembrane pigment-protein complex responsible for the first light-induced reactions in the photosynthetic process. We have found that PDA grows in colloidal form around the RC and in the appropriate conditions the protein is entrapped in the PDA matrix without loss of functionality. The protein is still capable to perform its natural photocycle leading to the generation of photocurrents and the ubiquinone acceptor complex function is modulated by the PDA/RC ratio.

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.

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 Cloning, Sequencing, and Characterization of the recAGene from Rhodopseudomonas viridis and Construction of arecA Strain

1998 ◽  
Vol 180 (12) ◽  
pp. 3227-3232 ◽  
Author(s):  
I-Peng Chen ◽  
Hartmut Michel
Keyword(s):  
Dna Damage ◽  
Rhizobium Meliloti ◽  
Photosynthetic Reaction Center ◽  
Reaction Centers ◽  
Photosynthetic Reaction Centers ◽  
Rhodopseudomonas Viridis ◽  
High Identity ◽  
Homologous Expression ◽  
Increased Sensitivity

ABSTRACT A recombination-deficient strain of the phototrophic bacteriumRhodopseudomonas viridis was constructed for the homologous expression of modified photosynthetic reaction center genes. TheR. viridis recA gene was cloned and subsequently deleted from the R. viridis genome. The clonedR. viridis recA gene shows high identity to knownrecA genes and was able to complement the Rec−phenotype of a Rhizobium meliloti recA strain. The constructed R. viridis recA strain showed the general Rec− phenotype, i.e., increased sensitivity to DNA damage and severely impaired recombination ability. The latter property of this strain will be of advantage in particular for expression of modified, nonfunctional photosynthetic reaction centers which are not as yet available.

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.

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