衣藻中光保护蛋白LhcSR实现非光化学能量猝灭的物理分子机理

Non-photochemical quenching (NPQ) is an energy dissipation process broadly employed by photosynthetic organisms for protection from high light photo-damage. NPQ is a common occurrence in nature as it constantly operates during most of the day-time. It effectively protects the photosynthetic organisms against high light stress, yet it decreases significantly the overall photosynthetic efficiency. Thus to decipher the protection mechanism is of great importance not only for our better understanding of the nature, but also for better usage of sunlight, optimizing the crops production and improving the biomass yield. In green algae, the LhcSR proteins are the key players. To protect the reaction centers, these proteins are triggered by the low luminal pH and dissipate the excess absorbed energy as harmless heat. However, the quenching mechanism and kinetics remain unclear. This lack of physical understanding is largely due to the high complexity of the in vivo system, which makes its characterization nearly impossible and the absence of a simpler in vitro system that could mimic the biological reality. Recently we have developed a system of isolated thylakoid membrane (an in vivo-like situation), which is able to undergo a complete NPQ process. In this proposal, we will take advantage of this system on which to perform ultrafast transient-absorption spectroscopic measurements to capture the quenching kinetics of chlorophylls in their excited energy state. By analyzing the kinetic curves, we aim to describe in detail the ultrafast kinetics of this NPQ process and from which gain more insight into the underlying physical and molecular mechanisms.

非光化学保护过程是指光合生物针对强光胁迫进行的一种光保护行为，广泛存在于自然界大多数光合生物，并实时发生在大部分日照时间内。它有效保障了光合生物安全生长，但同时也显著降低光合作用太阳能转化的总体效率。了解该过程运作的物理分子机制不仅有助于我们认识自然，也为未来提高太阳能利用效率、优化农业生产乃至发展绿色新能源提供必要的理论基础。在衣藻光保护过程中，细胞通过特定光保护蛋白LhcSR，将过量吸收的太阳光转化为热，避免光致损伤。目前该过程发生的物理机制尚不明确。研究瓶颈在于针对细胞体系的表征非常困难，而具有光保护生物功能的分离蛋白体系还尚未实现。申请人最近提取出具有光保护功能的类囊体膜，为该方面研究提供了简单生物体系。本项目拟利用该体系，结合超快光谱技术实现对该叶绿素激发态淬灭过程在位的飞秒瞬态吸收检测，并通过数据拟合和建模，揭示该光保护功能发生的动力学过程和能量猝灭机理。

非光化学保护过程是指光合生物针对强光胁迫进行的一种光保护行为，广泛存在于自然界的大多数光合生物中，该机制实时发生在大部分日照时间内，有效保障了光合生物安全生长，但同时由于它伴随着热量的损失，显著降低了光合作用太阳能转化的总体效率。了解该过程运作的物理分子机制不仅有助于我们认识自然，也为未来提高太阳能利用效率、优化农业生产乃至发展绿色新能源提供必要的理论基础。在衣藻光保护过程中，细胞通过特定光保护蛋白LhcSR，将过量吸收的太阳光转化为热.，避免光致损伤。目前该过程发生的物理机制尚不明确。研究瓶颈在于针对细胞体系的表征非常困难，而具有光保护生物功能的分离蛋白体系还尚未实现。申请人最近提取出具有光保护功能的类囊体膜，为该方面研究提供了简单生物体系。本项目利用该分离提纯体系，利用超快光谱技术成功实现了对该叶绿素激发态淬灭过程在位的飞秒瞬态吸收检测，并通过数据拟合和建模，揭示该光保护功能发生的动力学过程和能量猝灭机理，结果证明该能量猝灭过程很可能是由叶绿素的S1能级能量传递给叶黄素的S1能级进行的，这一发现与高等植物中通过LHCII聚集体研究得出的光保护的猝灭机理基本一致。 该研究是首次通过对光保护体系的原位超快光谱表征，排除了诸多人为引入的不确定性，从而加深人们对光保护过程的理解。