Photosynthetic light-harvesting antenna complexes (LHCs) of plants, moss and green algae form dyn... more Photosynthetic light-harvesting antenna complexes (LHCs) of plants, moss and green algae form dynamic switches between light harvesting and excitation-quenched, dissipative states. This mechanism protects the photosynthetic apparatus under light stress via a photo protective membrane response. Herein, we demonstrate the application of solid-state NMR spectroscopy to wild type, heterogeneous thylakoid membranes of Chlamydomonas reinhardtii (Cr) and purified Cr Light harvesting Complex II (LHCII) reconstituted in thylakoid lipid membranes, to detect the conformational dynamics of LHCII under native conditions. We find that membrane-reconstituted LHCII contains sites that undergo fast, large-amplitude motions, including the phytol tails of two chlorophylls. Furthermore, plasticity is observed in the N-terminal stretch and in the trans-membrane helical edges facing the thylakoid lumen. In intact thylakoids, the dynamics of these protein and pigment sites is significantly reduced. We con...
Industrial & Engineering Chemistry Research, 2019
The economic sustainability of microalgae-based processes is still a major issue hindering the in... more The economic sustainability of microalgae-based processes is still a major issue hindering the industrial application of such technologies. In this work, a mathematical model describing microalgae in varying light and temperature conditions is used to propose an optimised operation policy to increase productivity. The model is calibrated
In the last years new renewable energy sources started to be exploited to compensate exhausting f... more In the last years new renewable energy sources started to be exploited to compensate exhausting fossil fuels and minimize anthropogenic factors on climate change. Microalgae have reemerged as potential next-generation feedstock for biofuels and they are considered very promising on the long term, since they have a potentially high productivity per area and they can be grown on marginal land without competing with food crops. Our work is focused on the seawater microalga Nannochloropsis gaditana, which combines a fast growth rate with a strong accumulation of lipids and therefore yields great potential for these kinds of applications. Solar radiation provides all the energy supporting algae growth and lipids production and for this reason the available radiation must be exploited with the highest possible efficiency to optimize productivity and make their cultivation on a large scale competitive. Investigation of the bases affecting light use efficiency is thus seminal to elucidate t...
When exposed to saturating light conditions photosynthetic eukaryotes activate the xanthophyll cy... more When exposed to saturating light conditions photosynthetic eukaryotes activate the xanthophyll cycle where the carotenoid violaxanthin is converted into zeaxanthin by the enzyme violaxanthin de-epoxidase (VDE). VDE protein sequence includes 13 cysteine residues, 12 of which are strongly conserved in both land plants and algae. Site directed mutagenesis of Arabidopsis thaliana VDE showed that all these 12 conserved cysteines have a major role in protein function and their mutation leads to a strong reduction of activity. VDE is also shown to be active in its completely oxidized form presenting six disulfide bonds. Redox titration showed that VDE activity is sensitive to variation in redox potential, suggesting the possibility that dithiol/disulfide exchange reactions may represent a mechanism for VDE regulation.
ABSTRACT Some species of unicellular algae are capable of accumulating large amount of lipids whi... more ABSTRACT Some species of unicellular algae are capable of accumulating large amount of lipids which can be exploited for the production of biodiesel. Their exploitation is highly interesting in the perspective of replacing at least partially fossil fuels. Unfortunately, algae large scale cultivation systems are still largely inefficient and strong research efforts are necessary to develop competitive production of biofuels from algae. One of the major factors influencing algae growth is light which provides all the energy supporting metabolism. For this reason a high light use efficiency is seminal for developing any competitive algae cultivation system. In this chapter the most recent work on the influence of illumination environment on algae growth and lipids production is reviewed, focusing in particular on the species belonging to the genus Nannochloropsis, which are emerging as models for this kind of applications thanks to their remarkable productivity. Nannochloropsis showed the ability of growing efficiently under a wide range of illumination conditions, a fundamental property in the perspective of cultivation in outdoor photobioreactors. Light intensity do not directly influence lipids biosynthesis but it plays a strong indirect role when combined with other factors like increased carbon dioxide supply.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2014
Nannochloropsis gaditana belongs to Eustigmatophyceae, a class of eukaryotic algae resulting from... more Nannochloropsis gaditana belongs to Eustigmatophyceae, a class of eukaryotic algae resulting from a secondary endosymbiotic event. Species of this class have been poorly characterized thus far but are now raising increasing interest in the scientific community because of their possible application in biofuel production. Nannochloropsis species have a peculiar photosynthetic apparatus characterized by the presence of only chlorophyll a, with violaxanthin and vaucheriaxanthin esters as the most abundant carotenoids. In this study, the photosynthetic apparatus of this species was analyzed by purifying the thylakoids and isolating the different pigment-binding complexes upon mild solubilization. The results from the biochemical and spectroscopic characterization showed that the photosystem II antenna is loosely bound to the reaction center, whereas the association is stronger in photosystem I, with the antenna-reaction center super-complexes surviving purification. Such a supramolecular organization was found to be conserved in photosystem I from several other photosynthetic eukaryotes, even though these taxa are evolutionarily distant. A hypothesis on the possible selective advantage of different associations of the antenna complexes of photosystems I and II is discussed.
In a few years, space telescopes will investigate our Galaxy to detect evidence of life, mainly b... more In a few years, space telescopes will investigate our Galaxy to detect evidence of life, mainly by observing rocky planets. In the last decade, the observation of exoplanet atmospheres and the theoretical works on biosignature gasses have experienced a considerable acceleration. The most attractive feature of the realm of exoplanets is that 40% of M dwarfs host super-Earths with a minimum mass between 1 and 30 Earth masses, orbital periods shorter than 50 days, and radii between those of the Earth and Neptune (1–3.8 R⊕). Moreover, the recent finding of cyanobacteria able to use far-red (FR) light for oxygenic photosynthesis due to the synthesis of chlorophylls d and f, extending in vivo light absorption up to 750 nm, suggests the possibility of exotic photosynthesis in planets around M dwarfs. Using innovative laboratory instrumentation, we exposed different cyanobacteria to an M dwarf star simulated irradiation, comparing their responses to those under solar and FR simulated lights...
When exposed to saturating light conditions photosynthetic eukaryotes activate the xanthophyll cy... more When exposed to saturating light conditions photosynthetic eukaryotes activate the xanthophyll cycle where the carotenoid violaxanthin is converted into zeaxanthin by the enzyme violaxanthin de-epoxidase (VDE). VDE protein sequence includes 13 cysteine residues, 12 of which are strongly conserved in both land plants and algae. Site directed mutagenesis of Arabidopsis thaliana VDE showed that all these 12 conserved cysteines have a major role in protein function and their mutation leads to a strong reduction of activity. VDE is also shown to be active in its completely oxidized form presenting six disulfide bonds. Redox titration showed that VDE activity is sensitive to variation in redox potential, suggesting the possibility that dithiol/disulfide exchange reactions may represent a mechanism for VDE regulation.
In the last years new renewable energy sources started to be exploited to compensate exhausting f... more In the last years new renewable energy sources started to be exploited to compensate exhausting fossil fuels and minimize anthropogenic factors on climate change. Microalgae have reemerged as potential next-generation feedstock for biofuels and they are considered very promising on the long term, since they have a potentially high productivity per area and they can be grown on marginal land without competing with food crops. Our work is focused on the seawater microalga Nannochloropsis gaditana, which combines a fast growth rate with a strong accumulation of lipids and therefore yields great potential for these kinds of applications. Solar radiation provides all the energy supporting algae growth and lipids production and for this reason the available radiation must be exploited with the highest possible efficiency to optimize productivity and make their cultivation on a large scale competitive. Investigation of the bases affecting light use efficiency is thus seminal to elucidate t...
When exposed to saturating light conditions photosynthetic eukaryotes activate the xanthophyll cy... more When exposed to saturating light conditions photosynthetic eukaryotes activate the xanthophyll cycle where the carotenoid violaxanthin is converted into zeaxanthin by the enzyme violaxanthin de-epoxidase (VDE). VDE protein sequence includes 13 cysteine residues, 12 of which are strongly conserved in both land plants and algae. Site directed mutagenesis of Arabidopsis thaliana VDE showed that all these 12 conserved cysteines have a major role in protein function and their mutation leads to a strong reduction of activity. VDE is also shown to be active in its completely oxidized form presenting six disulfide bonds. Redox titration showed that VDE activity is sensitive to variation in redox potential, suggesting the possibility that dithiol/disulfide exchange reactions may represent a mechanism for VDE regulation.
Photosynthetic light-harvesting antenna complexes (LHCs) of plants, moss and green algae form dyn... more Photosynthetic light-harvesting antenna complexes (LHCs) of plants, moss and green algae form dynamic switches between light harvesting and excitation-quenched, dissipative states. This mechanism protects the photosynthetic apparatus under light stress via a photo protective membrane response. Herein, we demonstrate the application of solid-state NMR spectroscopy to wild type, heterogeneous thylakoid membranes of Chlamydomonas reinhardtii (Cr) and purified Cr Light harvesting Complex II (LHCII) reconstituted in thylakoid lipid membranes, to detect the conformational dynamics of LHCII under native conditions. We find that membrane-reconstituted LHCII contains sites that undergo fast, large-amplitude motions, including the phytol tails of two chlorophylls. Furthermore, plasticity is observed in the N-terminal stretch and in the trans-membrane helical edges facing the thylakoid lumen. In intact thylakoids, the dynamics of these protein and pigment sites is significantly reduced. We con...
Industrial & Engineering Chemistry Research, 2019
The economic sustainability of microalgae-based processes is still a major issue hindering the in... more The economic sustainability of microalgae-based processes is still a major issue hindering the industrial application of such technologies. In this work, a mathematical model describing microalgae in varying light and temperature conditions is used to propose an optimised operation policy to increase productivity. The model is calibrated
In the last years new renewable energy sources started to be exploited to compensate exhausting f... more In the last years new renewable energy sources started to be exploited to compensate exhausting fossil fuels and minimize anthropogenic factors on climate change. Microalgae have reemerged as potential next-generation feedstock for biofuels and they are considered very promising on the long term, since they have a potentially high productivity per area and they can be grown on marginal land without competing with food crops. Our work is focused on the seawater microalga Nannochloropsis gaditana, which combines a fast growth rate with a strong accumulation of lipids and therefore yields great potential for these kinds of applications. Solar radiation provides all the energy supporting algae growth and lipids production and for this reason the available radiation must be exploited with the highest possible efficiency to optimize productivity and make their cultivation on a large scale competitive. Investigation of the bases affecting light use efficiency is thus seminal to elucidate t...
When exposed to saturating light conditions photosynthetic eukaryotes activate the xanthophyll cy... more When exposed to saturating light conditions photosynthetic eukaryotes activate the xanthophyll cycle where the carotenoid violaxanthin is converted into zeaxanthin by the enzyme violaxanthin de-epoxidase (VDE). VDE protein sequence includes 13 cysteine residues, 12 of which are strongly conserved in both land plants and algae. Site directed mutagenesis of Arabidopsis thaliana VDE showed that all these 12 conserved cysteines have a major role in protein function and their mutation leads to a strong reduction of activity. VDE is also shown to be active in its completely oxidized form presenting six disulfide bonds. Redox titration showed that VDE activity is sensitive to variation in redox potential, suggesting the possibility that dithiol/disulfide exchange reactions may represent a mechanism for VDE regulation.
ABSTRACT Some species of unicellular algae are capable of accumulating large amount of lipids whi... more ABSTRACT Some species of unicellular algae are capable of accumulating large amount of lipids which can be exploited for the production of biodiesel. Their exploitation is highly interesting in the perspective of replacing at least partially fossil fuels. Unfortunately, algae large scale cultivation systems are still largely inefficient and strong research efforts are necessary to develop competitive production of biofuels from algae. One of the major factors influencing algae growth is light which provides all the energy supporting metabolism. For this reason a high light use efficiency is seminal for developing any competitive algae cultivation system. In this chapter the most recent work on the influence of illumination environment on algae growth and lipids production is reviewed, focusing in particular on the species belonging to the genus Nannochloropsis, which are emerging as models for this kind of applications thanks to their remarkable productivity. Nannochloropsis showed the ability of growing efficiently under a wide range of illumination conditions, a fundamental property in the perspective of cultivation in outdoor photobioreactors. Light intensity do not directly influence lipids biosynthesis but it plays a strong indirect role when combined with other factors like increased carbon dioxide supply.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2014
Nannochloropsis gaditana belongs to Eustigmatophyceae, a class of eukaryotic algae resulting from... more Nannochloropsis gaditana belongs to Eustigmatophyceae, a class of eukaryotic algae resulting from a secondary endosymbiotic event. Species of this class have been poorly characterized thus far but are now raising increasing interest in the scientific community because of their possible application in biofuel production. Nannochloropsis species have a peculiar photosynthetic apparatus characterized by the presence of only chlorophyll a, with violaxanthin and vaucheriaxanthin esters as the most abundant carotenoids. In this study, the photosynthetic apparatus of this species was analyzed by purifying the thylakoids and isolating the different pigment-binding complexes upon mild solubilization. The results from the biochemical and spectroscopic characterization showed that the photosystem II antenna is loosely bound to the reaction center, whereas the association is stronger in photosystem I, with the antenna-reaction center super-complexes surviving purification. Such a supramolecular organization was found to be conserved in photosystem I from several other photosynthetic eukaryotes, even though these taxa are evolutionarily distant. A hypothesis on the possible selective advantage of different associations of the antenna complexes of photosystems I and II is discussed.
In a few years, space telescopes will investigate our Galaxy to detect evidence of life, mainly b... more In a few years, space telescopes will investigate our Galaxy to detect evidence of life, mainly by observing rocky planets. In the last decade, the observation of exoplanet atmospheres and the theoretical works on biosignature gasses have experienced a considerable acceleration. The most attractive feature of the realm of exoplanets is that 40% of M dwarfs host super-Earths with a minimum mass between 1 and 30 Earth masses, orbital periods shorter than 50 days, and radii between those of the Earth and Neptune (1–3.8 R⊕). Moreover, the recent finding of cyanobacteria able to use far-red (FR) light for oxygenic photosynthesis due to the synthesis of chlorophylls d and f, extending in vivo light absorption up to 750 nm, suggests the possibility of exotic photosynthesis in planets around M dwarfs. Using innovative laboratory instrumentation, we exposed different cyanobacteria to an M dwarf star simulated irradiation, comparing their responses to those under solar and FR simulated lights...
When exposed to saturating light conditions photosynthetic eukaryotes activate the xanthophyll cy... more When exposed to saturating light conditions photosynthetic eukaryotes activate the xanthophyll cycle where the carotenoid violaxanthin is converted into zeaxanthin by the enzyme violaxanthin de-epoxidase (VDE). VDE protein sequence includes 13 cysteine residues, 12 of which are strongly conserved in both land plants and algae. Site directed mutagenesis of Arabidopsis thaliana VDE showed that all these 12 conserved cysteines have a major role in protein function and their mutation leads to a strong reduction of activity. VDE is also shown to be active in its completely oxidized form presenting six disulfide bonds. Redox titration showed that VDE activity is sensitive to variation in redox potential, suggesting the possibility that dithiol/disulfide exchange reactions may represent a mechanism for VDE regulation.
In the last years new renewable energy sources started to be exploited to compensate exhausting f... more In the last years new renewable energy sources started to be exploited to compensate exhausting fossil fuels and minimize anthropogenic factors on climate change. Microalgae have reemerged as potential next-generation feedstock for biofuels and they are considered very promising on the long term, since they have a potentially high productivity per area and they can be grown on marginal land without competing with food crops. Our work is focused on the seawater microalga Nannochloropsis gaditana, which combines a fast growth rate with a strong accumulation of lipids and therefore yields great potential for these kinds of applications. Solar radiation provides all the energy supporting algae growth and lipids production and for this reason the available radiation must be exploited with the highest possible efficiency to optimize productivity and make their cultivation on a large scale competitive. Investigation of the bases affecting light use efficiency is thus seminal to elucidate t...
When exposed to saturating light conditions photosynthetic eukaryotes activate the xanthophyll cy... more When exposed to saturating light conditions photosynthetic eukaryotes activate the xanthophyll cycle where the carotenoid violaxanthin is converted into zeaxanthin by the enzyme violaxanthin de-epoxidase (VDE). VDE protein sequence includes 13 cysteine residues, 12 of which are strongly conserved in both land plants and algae. Site directed mutagenesis of Arabidopsis thaliana VDE showed that all these 12 conserved cysteines have a major role in protein function and their mutation leads to a strong reduction of activity. VDE is also shown to be active in its completely oxidized form presenting six disulfide bonds. Redox titration showed that VDE activity is sensitive to variation in redox potential, suggesting the possibility that dithiol/disulfide exchange reactions may represent a mechanism for VDE regulation.
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