Differential sensitivity to oxygen among the bacteriochlorophylls g in the type-I reaction centers of Heliobacterium modesticaldum

The type-I, homodimeric photosynthetic reaction center (RC) of Heliobacteria (HbRC) is the only known RC in which bacteriochlorophyll g (BChl g) is found. It is also simpler than other RCs, having the smallest number of protein subunits and bound chromophores of any type-I RC. In the presence of oxygen, BChl g isomerizes to 81-hydroxychlorophyll aF (Chl aF). This naturally occurring process provides a way of altering the chlorophylls and studying the effect of these changes on energy and electron transfer. Transient absorbance difference spectroscopy reveals that triplet-state formation occurs in the antenna chlorophylls of HbRCs but does not provide site-specific information. Here, we report on an extended optically detected magnetic resonance (ODMR) study of the antenna triplet states in HbRCs with differing levels of conversion of BChl g to Chl aF. The data reveal pools of BChl g molecules with different triplet zero-field splitting parameters and different susceptibilities to chemical oxidation. By relating the detailed spectroscopic characteristics derived from the ODMR data to the recently solved crystallographic structure, we have tentatively identified BChl g molecules in which the probability of triplet formation is high and sites at which BChl g conversion is more likely, providing useful information about the fate of the excitation in the complex.

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Work Title Differential sensitivity to oxygen among the bacteriochlorophylls g in the type-I reaction centers of Heliobacterium modesticaldum
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Open Access
Creators
  1. Alessandro Agostini
  2. Marco Bortolus
  3. Bryan Ferlez
  4. Karim Walters
  5. John H. Golbeck
  6. Art van der Est
  7. Donatella Carbonera
License In Copyright (Rights Reserved)
Work Type Article
Publisher
  1. Photochemical and Photobiological Sciences
Publication Date June 1, 2021
Publisher Identifier (DOI)
  1. https://doi.org/10.1007/s43630-021-00049-3
Deposited November 15, 2021

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  • Created
  • Added Agostini_et_al._2021.pdf
  • Added Creator Alessandro Agostini
  • Added Creator Marco Bortolus
  • Added Creator Bryan Ferlez
  • Added Creator Karim Walters
  • Added Creator John H. Golbeck
  • Added Creator Art van der Est
  • Added Creator Donatella Carbonera
  • Published
  • Updated
  • Updated
  • Updated