DATE2025.06.20 #Press Releases

Quantum Transport Network Analysis Reveals the Significance of Chlorophyll Composition in Photosynthesis

Disclaimer: machine translated by DeepL which may contain errors.

— A strategy of “safety over efficiency” chosen by plants —

Summary

Plants have evolved to acquire the photosynthetic pigments chlorophyll a and chlorophyll b to perform photosynthesis. In the core complexes of photosynthesis, Photosystem I (PSI) and Photosystem II (PSII), only chlorophyll a is present. However, the light-harvesting antenna complex (LHCII), which plays a key role in capturing light energy, contains both chlorophyll a and chlorophyll b and contributes to the collection and transport of energy. The significance of having these two types of chlorophyll coexisting in their current ratio and spatial arrangement within LHCII, as well as the benefits derived from this arrangement, had remained an open question for many years.

Now, an international research team led by Assistant Professor Eunchul Kim (currently at Nihon University) and Professor Jun Minagawa of the National Institute for Basic Biology (NIBB), Professor Akihito Ishizaki of the Institute for Molecular Science (IMS) and the School of Science, The University of Tokyo, and Associate Professor Heetae Kim of Korea Institute of Energy Technology, has addressed this longstanding mystery using a novel approach called quantum transport network analysis, which visualizes the flow of energy at the molecular level. This method models energy transfer events between chlorophyll molecules based on quantum mechanics and network theory. By incorporating quantum effects such as delocalization (where energy exists across multiple molecules)—phenomena that have been overlooked in conventional analyses—this approach enables a more accurate understanding of the internal dynamics of photosynthesis. Moreover, by viewing the overall flow of energy as a "transportation network," the team succeeded in visualizing the design principles that allow plants to balance efficiency with risk avoidance by optimizing energy pathways and mitigating bottlenecks.

Using the molecular structure of the PSII-LHCII supercomplex—where PSII is associated with LHCII—the researchers constructed an energy transport network model on a computer. They then applied quantum dynamics calculations to this model, achieving for the first time a quantitative evaluation of energy flow within the supercomplex and the efficiency with which absorbed energy is utilized for photosynthesis. Their analysis revealed that the optimal spatial arrangement of chlorophyll a and chlorophyll b within LHCII not only enhances photosynthetic efficiency but also plays a critical role in activating photoprotective mechanisms under high-light conditions, such as strong sunlight. These findings suggest that green plants have evolved structural adaptations that prioritize not only “efficiency” but also “safety” (risk avoidance) in the design of their photosynthetic systems.

This research was published online in the U.S. international journal Science Advances on May 9, 2025.

Figure: Schematic representation of the study modeling the PSII-LHCII supercomplex as a network structure and analyzing the dynamics of energy transfer between chlorophyll molecules.

Related Links

National Institute for Basic Biology, Institute for Molecular Science, Quantum Life Science Institute

Published Journals

Journal Name	Science Advances
Title	Network analysis with quantum dynamics clarifies why photosystem II exploits both chlorophyll a and b