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Molecular Mechanisms of Nonphotochemical Quenching in the LHCSR3 Protein of Chlamydomonas reinhardtii.

Gabriel de la Cruz ValbuenaFranco V A CamargoRocio Borrego-VarillasFederico PerozeniCosimo D'AndreaMatteo BallottariGiulio Cerullo
Published in: The journal of physical chemistry letters (2019)
Photosynthetic organisms possess photoprotection mechanisms from excess light conditions. The fastest response consists in the pH-triggered activation of a dissipation channel of the energy absorbed by the chlorophylls into heat, called nonphotochemical quenching. In green algae, the pigment binding complex LHCSR3 acts both as a chlorophyll quencher and as a pH detector. In this work, we study the quenching of the LHCSR3 protein in vitro considering two different protein aggregation states and two pH conditions using a combination of picosecond time-resolved photoluminescence and femtosecond transient absorption in the visible and NIR spectral regions. We find that the mechanisms at the basis of LHCSR3 quenching activity are always active, even at pH 7.5 and low aggregation. However, quenching efficiency is strongly enhanced by pH and by aggregation conditions. In particular, we find that electron transfer from carotenoids to chlorophylls is enhanced at low pH, while quenching mediated by protein-protein interactions is increased by going to a high aggregation state. We also observe a weak pH-dependent energy transfer from the chlorophylls to the S1 state of carotenoids.
Keyphrases
  • energy transfer
  • quantum dots
  • protein protein
  • amino acid
  • small molecule
  • magnetic resonance
  • binding protein
  • electron transfer
  • multidrug resistant
  • gram negative
  • transcription factor
  • blood brain barrier
  • water soluble