- 學位論文
PSII複合體光捕捉動力學的理論研究
A Theoretical Study on Dynamics of Light Harvesting in Photosystem II Supercomplex
若您是本文的作者，可授權文章由華藝線上圖書館中協助推廣。
摘要
光合作用系統 II (PSII)仰賴一個巨大的天線複合體用以蒐集充足的光能，這些光能能夠驅動光合作用系統II中的反應中心 (RCs)。在這個光捕捉的過程中，太陽光會激發天線複合體中的色素分子，將光能轉換成激發能。然而，在激發能從天線複合體轉移到RCs的過程中，蛋白質結構的振動會擾動各個色素分子的激發能，從而在PSII上形成一個波動的能量曲面。此外，巨大的天線複合體中的色素分子數目遠遠超過RC中的數目，這樣的差異使得巨大的天線複合體具有更高的自由度，同時也產生了相對應的熵效應。即便在這些限制下，PSII仍能在光捕捉的過程中保持高量子效率。因此，我們需要瞭解大自然使用了哪些策略。了解這些策略對於我們理解PSII如何在限制條件下實現高效能光捕捉至關重要。為此，我們建立了一個光合作用系統II激發能轉移的簡化群集模型，我們能夠建立有效的內能能量曲面。從這個能量曲面上，我們發現在群集中有一些特殊的時標分離(timescale separation)的性質，降低了激發能在天線複合體中的自由度並促進激發能進入反應中心。另外，光合作用系統II在其主要的能量轉移路徑上設計了精巧的能量梯度，這些優化能量曲面的設計是用來達成高效地光捕捉。同時，PSII還利用熱能來克服激發能擾動所產生的障礙。透過研究PSII能量曲面的優化設計，我們可以為未來設計大型高效光捕捉系統提供一些有價值的指引。
並列摘要
Photosystem II (PSII) relies on a large antenna complex to collect sufficient light energy to power its reaction centers (RCs). In this light harvesting process, molecular excitation must pass through the fluctuating energy surface where the static disorder perturb site energies, and overcome unfavorable entropic effects to be transferred from the large antenna to the much smaller RC with low energy loss. It is thus of significant importance to uncover the strategies that the nature applied to achieve the remarkably high quantum efficiency of PSII under the constrains. To this end, we constructed a coarse-grained model for exciton energy transfer in PSII, which allows us to establish an effective internal energy surface for excitation energy transfer in the PSII. We found that the energy landscape exhibits timescale separation characteristics among the clusters, which suppresses the entropic effect and facilitates the energy transfer to the RC. Further investigation revealed that the energy surface is optimized for efficient light harvesting and tolerating static disorder of site energy by using a specifically designed energy gradient along the main energy-transfer pathways and utilization of thermal energy to overcome the barriers. The optimal energy landscape for EET in the PSII provides important insight towards how to achieve highly efficient energy harvesting in a large and fluctuating system.
參考文獻
[1] Roberta Croce and Herbert van Amerongen. Light harvesting in oxygenic photosynthesis: Structural biology meets spectroscopy. Science, 369(6506):eaay2058, 2020.
[2] Roman Kouřil, Jan P Dekker, and Egbert J Boekema. Supramolecular organization of photosystem II in green plants. Biochim. Biophys. Acta Bioenerg., 1817(1):2–12, 2012.
[3] Cristina Pagliano, Guido Saracco, and James Barber. Structural, functional and auxiliary proteins of photosystem ii. Photosynth. Res., 116:167–188, 2013.
[4] Xiaodong Su, Jun Ma, Xuepeng Wei, Peng Cao, Dongjie Zhu, Wenrui Chang, Zhenfeng Liu, Xinzheng Zhang, and Mei Li. Structure and assembly mechanism of plant c2s2m2type psIILHCII supercomplex. Science, 357(6353):815–820, 2017.
[5] Jan P Dekker and Egbert J Boekema. Supramolecular organization of thylakoid membrane proteins in green plants. Biochim. Biophys. Acta Bioenerg.,1706(12): 12–39, 2005.