Dipartimento di Fisica, Università di Modena e Reggio Emilia, via Campi, 213/a, 41125 Modena, Italy.
CNR NANO S3, Via Campi 213/A, 41125 Modena, Italy.
J R Soc Interface. 2020 Nov;17(172):20200813. doi: 10.1098/rsif.2020.0813. Epub 2020 Nov 11.
In this paper, we model the excitation energy transfer (EET) of photosystem I (PSI) of the common pea plant as a complex interacting network. The magnitude of the link energy transfer between nodes/chromophores is computed by Forster resonant energy transfer (FRET) using the pairwise physical distances between chromophores from the PDB 5L8R (Protein Data Bank). We measure the global PSI network EET efficiency adopting well-known network theory indicators: the network efficiency (Eff) and the largest connected component (LCC). We also account the number of connected nodes/chromophores to P700 (CN), a new ad hoc measure we introduce here to indicate how many nodes in the network can actually transfer energy to the P700 reaction centre. We find that when progressively removing the weak links of lower EET, the Eff decreases, while the EET paths integrity (LCC and CN) is still preserved. This finding would show that the PSI is a resilient system owning a large window of functioning feasibility and it is completely impaired only when removing most of the network links. From the study of different types of chromophore, we propose different primary functions within the PSI system: chlorophyll (CLA) molecules are the central nodes in the EET process, while other chromophore types have different primary functions. Furthermore, we perform nodes removal simulations to understand how the nodes/chromophores malfunctioning may affect PSI functioning. We discover that the removal of the CLA triggers the fastest decrease in the Eff, confirming that CAL is the main contributors to the high EET efficiency. Our outcomes open new perspectives of research, such comparing the PSI energy transfer efficiency of different natural and agricultural plant species and investigating the light-harvesting mechanisms of artificial photosynthesis both in plant agriculture and in the field of solar energy applications.
在本文中，我们将普通豌豆植物的光系统 I (PSI) 的激发能量转移 (EET) 建模为一个复杂的相互作用网络。节点/发色团之间的链接能量转移的大小通过使用来自 PDB 5L8R（蛋白质数据库）的发色团之间的成对物理距离的Förster 共振能量转移 (FRET) 来计算。我们采用著名的网络理论指标来测量全局 PSI 网络 EET 效率：网络效率 (Eff) 和最大连通分量 (LCC)。我们还考虑了与 P700（CN）连接的节点/发色团的数量，这是我们在这里引入的一个新的特定指标，用于指示网络中实际上有多少节点可以将能量转移到 P700 反应中心。我们发现，当逐步去除低 EET 的弱链接时，Eff 会降低，而 EET 路径完整性（LCC 和 CN）仍然保留。这一发现表明，PSI 是一个具有较大功能可行性窗口的有弹性系统，只有当去除大部分网络链接时才会完全受损。从不同类型的发色团的研究中，我们提出了 PSI 系统内的不同主要功能：叶绿素 (CLA) 分子是 EET 过程中的中心节点，而其他发色团类型具有不同的主要功能。此外，我们进行了节点去除模拟，以了解节点/发色团的故障可能如何影响 PSI 的功能。我们发现，CLA 的去除会导致 Eff 下降最快，这证实了 CAL 是高 EET 效率的主要贡献者。我们的研究结果为研究开辟了新的视角，例如比较不同自然和农业植物物种的 PSI 能量转移效率，以及研究人工光合作用的光捕获机制，包括在植物农业和太阳能应用领域。
