Tuning antenna function through hydrogen bonds to chlorophyll a

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Llansola-Portoles, Manuel J. | Pascal, Andrew A. | Llansola-Portoles, Manuel, J. | Li, Fei | Xu, Pengqi | Streckaite, Simona | Ilioaia, Cristian | Yang, Chunhong | Gall, Andrew | Croce, Roberta | Robert, Bruno | Pascal, Andrew, A

Edité par CCSD ; Elsevier -

International audience. We describe a molecular mechanism tuning the functional properties of chlorophyll a (Chl-a) molecules in photosynthetic antenna proteins. Light-harvesting complexes from photosystem II in higher plants - specifically LHCII purified with α- or β-dodecyl-maltoside, along with CP29 - were probed by low-temperature absorption and resonance Raman spectroscopies. We show that hydrogen bonding to the conjugated keto carbonyl group of protein-bound Chl-a tunes the energy of its Soret and Qy absorption transitions, inducing red-shifts that are proportional to the strength of the hydrogen bond involved. Chls-a with non-H-bonded keto C131 groups exhibit the blue-most absorption bands, while both transitions are progressively red-shifted with increasing hydrogen-bonding strength - by up 382 & 605 cm-1 in the Qy and Soret band, respectively. These hydrogen bonds thus tune the site energy of Chl-a in light-harvesting proteins, determining (at least in part) the cascade of energy transfer events in these complexes.

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