In this paper, we model the excitation energy transfer (EET) of photosystem I (PSI) of the common pea plant Pisum sativum 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 a (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.

中文翻译：

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将光系统 I 建模为复杂的交互网络

在本文中，我们将普通豌豆植物 Pisum sativum 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/生色团之间的链接能量转移的大小是通过 Forster 共振能量转移 (FRET) 使用来自 PDB 5L8R（蛋白质数据库）的生色团之间的成对物理距离计算的。我们采用众所周知的网络理论指标来衡量全球 PSI 网络 EET 效率：网络效率（Eff）和最大连通分量（LCC）。我们还将连接节点/发色团的数量计入 P700 (CN)，这是我们在此引入的一种新的临时措施，以表明网络中有多少节点可以实际将能量传输到 P700 反应中心。我们发现，当逐步去除较低 EET 的薄弱环节时，Eff 会降低，而 EET 路径完整性（LCC 和 CN）仍然保留。这一发现将表明 PSI 是一个弹性系统，拥有一个大的功能可行性窗口，并且只有在移除大部分网络链接时才会完全受损。通过对不同类型发色团的研究，我们提出了 PSI 系统内不同的主要功能：叶绿素 a (CLA) 分子是 EET 过程中的中心节点，而其他类型的发色团具有不同的主要功能。此外，我们执行节点移除模拟以了解节点/发色团故障如何影响 PSI 功能。我们发现 CLA 的去除触发了 Eff 的最快下降，证实了 CAL 是高 EET 效率的主要贡献者。我们的成果开辟了新的研究视角，