Papers by Gabriel de la Cruz Valbuena
The Journal of Physical Chemistry Letters
Light-harvesting complex stress-related (LHCSR) proteins in green algae are essential for photopr... more Light-harvesting complex stress-related (LHCSR) proteins in green algae are essential for photoprotection via a non-photochemical quenching (NPQ), playing the dual roles of pH sensing and dissipation of chlorophylls excited-state energy. pH sensing occurs via a protonation of acidic residues located mainly on its lumen-exposed C-terminus. Here, we combine in vivo and in vitro studies to ascertain the role in NPQ of these protonatable C-terminal residues in LHCSR3 from Chlamydomonas reinhardtii. In vivo studies show that four of the residues, D239, D240, E242, and D244, are not involved in NPQ. In vitro experiments on an LHCSR3 chimeric protein, obtained by a substitution of the C terminal with that of another LHC protein lacking acidic residues, show a reduction of NPQ compared to the wild type but preserve the quenching mechanism involving a charge transfer from carotenoids to chlorophylls. NPQ in LHCSR3 is thus a complex mechanism, composed of multiple contributions triggered by different acidic residues.
Metadata of "Incorporating a molecular antenna in diatom microalgae cells enhances photosynt... more Metadata of "Incorporating a molecular antenna in diatom microalgae cells enhances photosynthesis"
2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2019
The survival of photosynthetical organisms crucially depends on their ability to adapt to differe... more The survival of photosynthetical organisms crucially depends on their ability to adapt to different light intensities. Under excess light conditions, the fastest photoprotection response consists in the turn-on of a dissipation mechanism of the energy absorbed by the chlorophylls into heat, called non-photochemical quenching (NPQ). NPQ requires the action of an intrathylakoidal protein, LHCSR3, composed of different chlorophylls and carotenoids bound to a tri-helicoidal carbon chain. During the light phase of photosynthesis, high light stress conditions generate a pH gradient across the thylakoid membrane which is sensed by the acid groups of LHCSR3 and triggers the protein quenching activity In this work, we reproduce the quenching of the LHCSR3 protein in vitro considering two different pH conditions and two protein aggregation states (HA: high aggregation, LA: low aggregation). NPQ was studied using a combination of picosecond time-resolved photoluminescence (TRPL) and femtosecond transient absorption (TA) techniques in the visible and NIR spectral regions.
New Phytologist, 2020
Summary The xanthophyll cycle is the metabolic process by which the carotenoid violaxanthin is de... more Summary The xanthophyll cycle is the metabolic process by which the carotenoid violaxanthin is de‐epoxidated to zeaxanthin, a xanthophyll with a crucial photoprotective role in higher plants and mosses. The role of zeaxanthin is still unclear in green algae, and a peculiar violaxanthin de‐epoxidating enzyme was found in the model organism Chlamydomonas reinhardtii. Here, we investigated the molecular details and functions of the xanthophyll cycle in the case of Chlorella vulgaris, one of the green algae most considered for industrial cultivation, where resistance to high light stress is a prerequisite for sustainable biomass production. Identification of the violaxanthin de‐epoxidase enzyme in C. vulgaris was performed by genome mining and in vitro analysis of the catalytic activity of the gene product identified. The photoprotective role of zeaxanthin was then investigated in vivo and in isolated pigment‐binding complexes. The results obtained demonstrate the functioning, even thou...
ACS Sustainable Chemistry & Engineering, 2019
Photosystem I (PSI) is a pigment binding multi-subunit protein complex involved in the light phas... more Photosystem I (PSI) is a pigment binding multi-subunit protein complex involved in the light phase of photosynthesis, catalyzing a light dependent electron transfer reaction from plastocyanin to ferredoxin. PSI is characterized by a photochemical efficiency close to one, suggesting its possible application in light dependent redox reaction in extra-cellular context. The stability of PSI complexes isolated from plant cells is however Page 2 of 49 ACS Paragon Plus Environment ACS Sustainable Chemistry & Engineering 3 limited if not embedded in a protective environment. Here we show an innovative solution for exploiting the photochemical properties of PSI, by encapsulation of isolated PSI complexes in PLGA (poly lactic-co-glycolic acid) organic microparticles. These encapsulated PSI complexes were able to catalyze light dependent redox reactions with electron acceptors and donors outside the PLGA microparticles. Moreover, PSI complexes encapsulated in PLGA microparticles were characterized by a higher photochemical activity and stability compared to PSI complexes in detergent solution, suggesting their possible application for ex vivo photocatalysis.
The Journal of Physical Chemistry Letters, 2019
Photosynthetic organisms possess photoprotection mechanisms from excess light conditions. The fas... more 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 S 1 state of carotenoids.
Scientific Reports, 2021
Diatom microalgae have great industrial potential as next-generation sources of biomaterials and ... more Diatom microalgae have great industrial potential as next-generation sources of biomaterials and biofuels. Effective scale-up of their production can be pursued by enhancing the efficiency of their photosynthetic process in a way that increases the solar-to-biomass conversion yield. A proof-of-concept demonstration is given of the possibility of enhancing the light absorption of algae and of increasing their efficiency in photosynthesis by in vivo incorporation of an organic dye which acts as an antenna and enhances cells’ growth and biomass production without resorting to genetic modification. A molecular dye (Cy5) is incorporated in Thalassiosira weissflogii diatom cells by simply adding it to the culture medium and thus filling the orange gap that limits their absorption of sunlight. Cy5 enhances diatoms’ photosynthetic oxygen production and cell density by 49% and 40%, respectively. Cy5 incorporation also increases by 12% the algal lipid free fatty acid (FFA) production versus t...
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Papers by Gabriel de la Cruz Valbuena