Molecular mechanism of photodamages of chloroplast thylakoids

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Photosynthetic organisms suffer photodamages under the conditions where light energy is in excess of the electron acceptor. This project has been aimed at understanding under what conditions photodamages are enhanced, what is the primary target molecule, and by what molecular mechanism the target molecule is photodamaged. 1. Photodamages are enhanced under anaerogic conditions indicating that dioxygen works as the electron acceptor and suppresses photodzmages. 2. The primary target site of photodamages is identified to be the reaction center of photosystem II. This is also the case under anaerobic conditions indicating triplet excited molecules damage the target molecules without the participation of sctive oxygen. 3. Lysine endopeptides digestion allows to isolate and determine the D1 and D2 proteins of photosystem II reaction center. 4 In photodamaged thylakoids little fragmentation of D1 and D2 proteins occurs confirming that the proteins suffer damages of amino acid residues but ara not fragmented. 5. Functional size for the Mn-binding in photosystem was determined. The molecular mechanism of photooxidation of hydrogen peroxide in thylakoids was revealed. 6. Ascorbate peroxidase of spinach chloroplasts was purified and its molecular properties was determined. A review article for the production and scavenging of active oxygen in chloroplasts was described.