Solar energy harnessed by plants and algae has great potential to be converted into biofuels for future generations. Understanding the regulatory mechanism of photosynthesis can increase biomass... Show moreSolar energy harnessed by plants and algae has great potential to be converted into biofuels for future generations. Understanding the regulatory mechanism of photosynthesis can increase biomass yield and drive the generation of biofuels to its maximum. PsbS, a membrane protein, is an essential component for NPQ and has been studied extensively in this thesis. PsbS is hypothesized to sense pH and to regulate photosynthesis under light stress conditions. The first objective in this thesis is to produce, purify and refold recombinant PsbS with sufficiently high yields for biochemical studies along with optimizing the detergent conditions for maintaining its stability. The second objective is the spectroscopic characterization of PsbS to understand its role as a pH sensor and its molecular mechanism during photoprotection. Show less
Solar energy is used by photosynthetic organisms to drive energy required cellular processes. Is absorbed by two groups of pigments, located in the LHCs. These proteins are essential for the... Show moreSolar energy is used by photosynthetic organisms to drive energy required cellular processes. Is absorbed by two groups of pigments, located in the LHCs. These proteins are essential for the performance of photosynthesis, because they are involved in harvesting the light and because they protect the photosynthetic system from excess of light that cause photodamage. I performed in vitro studies mimicking the two functions of LHCII by inserting the protein in nanodiscs and in liposomes. I demonstrate that Chl excitation quenching is dependent on protein-protein interactions. I investigated the specific interactions of LHCII with PsbS. The fluorescence study of our minimal membrane models strongly suggests that the pH-dependent role of PsbS lies in creating membrane rearrangements and supercomplex remodeling that could facilitate LHCII aggregation quenching. I successfully produced 13C lutein-rLhcb1 protein in detergent, mimicking the unquenched state, and protein aggregates, mimicking the quenched state, were biochemically and spectroscopically characterized and further analysed with solid state NMR.Ring current shifts of the lutein head signals indicate that the heads are in close proximity to specific Chls (Chl a610 and Chl a602), providing for the first-time structural information about lutein-Chl interactions in LHCII in its unquenched state. Show less
