Molecular mechanism of photodamages of chloroplast thylakoids

在光能超过电子受体的条件下，光合作用生物遭受光损伤。这个项目的目的是了解在什么条件下光损伤被增强，什么是主要的靶分子，以及靶分子通过什么分子机制被光损伤。1.在厌氧条件下，光损伤增强，说明氧气作为电子受体，抑制光损伤。2.确定光损伤的主要靶点是光系统II的反应中心。在厌氧条件下也是如此，表明三重态激发的分子在没有稀有氧参与的情况下对靶分子造成损伤。3.赖氨酸内肽的消化可以分离和测定光系统II反应中心的D_1和D_2蛋白。4在光损伤的类囊体膜中，D_1和D_2蛋白几乎没有发生断裂，证实了蛋白质受到氨基酸残基的破坏，但Ara没有发生断裂。5.确定了光系统中锰结合的功能大小。揭示了类囊体过氧化氢光氧化的分子机制。6.对菠菜叶绿体抗坏血酸过氧化物酶进行了纯化，并对其分子性质进行了测定。对叶绿体中活性氧的产生和清除进行了综述。

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.