Modeling the photosynthetic system I as complex interacting network

In this paper we model the excitation energy transfer (EET) of the photosynthetic system I (PSI) of the common pea plant Pisum Sativum as 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 (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 find that when progressively removing the weak links of lower EET, the network efficiency (Eff) decreases while the EET paths integrity (LCC) 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. Furthermore, we perform nodes removal simulations to understand how the nodes-chromophores malfunctioning may affect the PSI functioning. We discover that the removal of the core chlorophylls triggers the fastest decrease in the network efficiency (Eff), unveiling them as the key component boosting 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.