光合成におけるコヒーレンスダイナミクス:刺激的コヒーレンスに対するタンパク質の保護
Hohjai Lee1, Yuan-Chung Cheng, Graham R Fleming
1Department of Chemistry and QB3 Institute, University of California, Berkeley, USA.
Science (New York, N.Y.)
|June 9, 2007
まとめ
光合成における量子相関性は,効率的なエネルギー転送の鍵です. 相関するタンパク質環境は,この電子的相関性を保ち,光合成複合体の中で効率的な光採集と捕獲を可能にします.
科学分野:
- * バイオフィジックス
- * 量子生物学について
- * 光合成の研究
背景:
- * 初期の光合成の効率における量子コヘランスの役割は,まだ未解決の問題である.
- * 一貫性ダイナミクスを理解することは,自然のシステムにおける非常に効率的な光エネルギー伝達の説明に不可欠です.
研究 の 目的:
- * 光合成の初期段階における量子コヘランスの役割を調査する.
- * 細菌の反応センターにおけるコヒーレンスダイナミクスを視覚化するために,高度なスペクトロスコーピーの技術を用いた.
主な方法:
- * 二色フォトンエコー実験を行った.
- * 細菌の反応センター内のコヒーレンスダイナミクスを直接視覚化しました.
主要な成果:
- * 混合バクテリオフェオフィチンと付属バクテリオクロロフィルの興奮状態の間の長時間持続する電子相関が明らかになった.
- * タンパク質によって引き起こされる変動の強い相関が,この観察された一貫性を説明することを示した.
- * 電子的一貫性の維持に不可欠な相関タンパク質環境を特定した.
結論:
- * 相関タンパク質環境は,光合成複合体の電子連結を維持する上で重要な役割を果たします.
- * この保たれたコヒーレンスにより,コヒーレントな興奮エネルギー転送が容易になり,効率的な光の採集と捕獲につながります.
- * 発見は,光合成の驚くべき効率のメカニズムを示唆しています.
関連する概念動画
01:32Photosystems
Photosystems are multiprotein complexes that form the functional units of photosynthesis in plants, algae, and cyanobacteria. They are found embedded in the membrane of tiny sac-like structures called thylakoids placed inside the chloroplast.
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
01:34The Z-Scheme of Electron Transport in Photosynthesis
The light reactions of photosynthesis assume a linear flow of electrons from water to NADP+. During this process, light energy drives the splitting of water molecules to produce oxygen. However, oxidation of water molecules is a thermodynamically unfavorable reaction and requires a strong oxidizing agent. This is accomplished by the first product of light reactions: oxidized P680 (or P680+), the most powerful oxidizing agent known in biology. The oxidized P680 that acquires an electron from the...
01:27Photosystem I
Although structurally similar to photosystem II (PSII), photosystem I (PSI) is has a different electron supplier and electron acceptor.
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
01:22Photosystem II
The multi-protein complex photosystem II (PS II) harvests photons and transfers their energy through its bound pigments to its reaction center, and ultimately to photosystem I (PSI) through the electron transport chain. The pigments responsible for caputirng the light energy in photosystems include chlorophyll a, chlorophyll b, and carotenoids.
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
01:15The Antenna Complex
Plants and other photosynthetic organisms comprise pigments capable of absorption of direct sunlight. These pigments are present in the reaction center - the main site of photochemical reactions as well as in the antenna complex. Under average light conditions, the rate at which reaction center pigments absorb light is far below the electron transport chain's capacity. As a result, the reaction center alone cannot provide enough energy to drive photosynthesis. The photosynthetic efficiency can...
01:29The Photochemical Reaction Center
Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center is a more appropriate term that describes these complexes. The Nobel laureates Robert Emerson and William Arnold provided the first experimental evidence of photochemical reaction centers by demonstrating the participation of nearly 2,500 chlorophyll molecules for the release of just one molecule of oxygen. Despite thousands of photosynthetic...