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Title: Overall energy conversion efficiency of a photosynthetic vesicle

Abstract

The chromatophore of purple bacteria is an intracellular spherical vesicle that exists in numerous copies in the cell and that efficiently converts sunlight into ATP synthesis, operating typically under low light conditions. Building on an atomic-level structural model of a low-light-adapted chromatophore vesicle from Rhodobacter sphaeroides, we investigate the cooperation between more than a hundred protein complexes in the vesicle. The steady-state ATP production rate as a function of incident light intensity is determined after identifying quinol turnover at the cytochrome bc1 complex (cytbc1) as rate limiting and assuming that the quinone/quinol pool of about 900 molecules acts in a quasi-stationary state. For an illumination condition equivalent to 1% of full sunlight, the vesicle exhibits an ATP production rate of 82 ATP molecules/s. The energy conversion efficiency of ATP synthesis at illuminations corresponding to 1%–5% of full sunlight is calculated to be 0.12-0.04, respectively. The vesicle stoichiometry, evolutionarily adapted to the low light intensities in the habitat of purple bacteria, is suboptimal for steady-state ATP turnover for the benefit of protection against over-illumination.

Authors:
 [1];  [2];  [3];  [4]; ORCiD logo [5]
  1. Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States; Department of Physics, University of Illinois at Urbana-Champaign, Urbana, United States
  2. Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States; Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, United States
  3. Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States
  4. Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, United Kingdom
  5. Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States; Department of Physics, University of Illinois at Urbana-Champaign, Urbana, United States; Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, United States
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Photosynthetic Antenna Research Center (PARC)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1388788
DOE Contract Number:
SC0001035
Resource Type:
Journal Article
Resource Relation:
Journal Name: eLife; Journal Volume: 5; Related Information: PARC partners with Washington University in St. Louis (lead); University of California, Riverside; University of Glasgow, UK; Los Alamos National Laboratory; University of New Mexico; New Mexico Corsortium; North Carolina State University; Northwestern University; Oak Ridge National Laboratory; University of Pennsylvania; Sandia National Laboratories; University of Sheffield, UK
Country of Publication:
United States
Language:
English
Subject:
solar (fuels), photosynthesis (natural and artificial), biofuels (including algae and biomass), bio-inspired, charge transport, membrane, synthesis (novel materials), synthesis (self-assembly)

Citation Formats

Sener, Melih, Strumpfer, Johan, Singharoy, Abhishek, Hunter, C. Neil, and Schulten, Klaus. Overall energy conversion efficiency of a photosynthetic vesicle. United States: N. p., 2016. Web. doi:10.7554/eLife.09541.
Sener, Melih, Strumpfer, Johan, Singharoy, Abhishek, Hunter, C. Neil, & Schulten, Klaus. Overall energy conversion efficiency of a photosynthetic vesicle. United States. doi:10.7554/eLife.09541.
Sener, Melih, Strumpfer, Johan, Singharoy, Abhishek, Hunter, C. Neil, and Schulten, Klaus. 2016. "Overall energy conversion efficiency of a photosynthetic vesicle". United States. doi:10.7554/eLife.09541.
@article{osti_1388788,
title = {Overall energy conversion efficiency of a photosynthetic vesicle},
author = {Sener, Melih and Strumpfer, Johan and Singharoy, Abhishek and Hunter, C. Neil and Schulten, Klaus},
abstractNote = {The chromatophore of purple bacteria is an intracellular spherical vesicle that exists in numerous copies in the cell and that efficiently converts sunlight into ATP synthesis, operating typically under low light conditions. Building on an atomic-level structural model of a low-light-adapted chromatophore vesicle from Rhodobacter sphaeroides, we investigate the cooperation between more than a hundred protein complexes in the vesicle. The steady-state ATP production rate as a function of incident light intensity is determined after identifying quinol turnover at the cytochrome bc1 complex (cytbc1) as rate limiting and assuming that the quinone/quinol pool of about 900 molecules acts in a quasi-stationary state. For an illumination condition equivalent to 1% of full sunlight, the vesicle exhibits an ATP production rate of 82 ATP molecules/s. The energy conversion efficiency of ATP synthesis at illuminations corresponding to 1%–5% of full sunlight is calculated to be 0.12-0.04, respectively. The vesicle stoichiometry, evolutionarily adapted to the low light intensities in the habitat of purple bacteria, is suboptimal for steady-state ATP turnover for the benefit of protection against over-illumination.},
doi = {10.7554/eLife.09541},
journal = {eLife},
number = ,
volume = 5,
place = {United States},
year = 2016,
month = 8
}
  • The chromatophore of purple bacteria is an intracellular spherical vesicle that exists in numerous copies in the cell and that efficiently converts sunlight into ATP synthesis, operating typically under low light conditions. Building on an atomic-level structural model of a low-light-adapted chromatophore vesicle from Rhodobacter sphaeroides , we investigate the cooperation between more than a hundred protein complexes in the vesicle. The steady-state ATP production rate as a function of incident light intensity is determined after identifying quinol turnover at the cytochrome bc1 complex (cytb⁢c1) as rate limiting and assuming that the quinone/quinol pool of about 900 molecules acts inmore » a quasi-stationary state. For an illumination condition equivalent to 1% of full sunlight, the vesicle exhibits an ATP production rate of 82 ATP molecules/s. The energy conversion efficiency of ATP synthesis at illuminations corresponding to 1%–5% of full sunlight is calculated to be 0.12–0.04, respectively. The vesicle stoichiometry, evolutionarily adapted to the low light intensities in the habitat of purple bacteria, is suboptimal for steady-state ATP turnover for the benefit of protection against over-illumination.« less
  • The chromatophore of purple bacteria is an intracellular spherical vesicle that exists in numerous copies in the cell and that efficiently converts sunlight into ATP synthesis, operating typically under low light conditions. Building on an atomic-level structural model of a low-light-adapted chromatophore vesicle from Rhodobacter sphaeroides , we investigate the cooperation between more than a hundred protein complexes in the vesicle. The steady-state ATP production rate as a function of incident light intensity is determined after identifying quinol turnover at the cytochrome bc1 complex (cytb⁢c1) as rate limiting and assuming that the quinone/quinol pool of about 900 molecules acts inmore » a quasi-stationary state. For an illumination condition equivalent to 1% of full sunlight, the vesicle exhibits an ATP production rate of 82 ATP molecules/s. The energy conversion efficiency of ATP synthesis at illuminations corresponding to 1%–5% of full sunlight is calculated to be 0.12–0.04, respectively. The vesicle stoichiometry, evolutionarily adapted to the low light intensities in the habitat of purple bacteria, is suboptimal for steady-state ATP turnover for the benefit of protection against over-illumination.« less
  • The authors construct algorithms for calculating and optimizing the overall energy efficiency of nuclear power plants which are based on hydraulic and heat transfer considerations and reactor lattice parameters as well as fuel management and cycle and reactor fueling options including spent fuels reprocessing. They generalize their algorithms to a number of reactor efficiency scenarios including thermal neutron, LMFBR, fast, and WWER type reactors. The algorithms, for the case of breeder reactors, also incorporate breeding ratio parameters.
  • The photoelectrochemical behavior of chlorophyll (Chl) a and b monolayers, deposited on SnO/sub 2/ optically transparent electrodes by means of the Langmuir--Blodgett technique, has been investigated. Photocurrents and photovoltages were always anodic and negative, respectively, corresponding to an electron injection from excited Chl molecules to the conduction band of SnO/sub 2/. Spectra of photocurrents and photovoltages coincided well with the absorption spectra of Chl monolayers at the SnO/sub 2/-solution interface. Effects of light intensity, electrode potential, redox agents added, and solution pH on the magnitude of the photocurrent were studied in detail. The quantum efficiency for photocurrent generation was measuredmore » with Chl a--stearic acid mixed monolayers, and a highest value of 12 to 16% was attained at the Chl a/stearic acid molar ratio of ca. 1.0. The usefulness of the present system for an in vitro simulation of photosynthetic primary processes is suggested. 2 tables; 16 figures.« less