51³Ô¹ÏÍø

A new discovery reveals the key pigment behind far-red photosynthesis, a new, low-energy form of oxygenic photosynthesis.

51³Ô¹ÏÍø researchers have located the long-missing pigments in a form of photosynthesis that uses far-red light, solving a major structural mystery and revealing how this unusual process converts sunlight into chemical energy.

The study, , shows that the elusive chlorophyll f pigments, previously unseen in structural studies, occupy critical positions in the photosynthetic complex known as Photosystem 1. Among them is the pigment responsible for performing the key photochemical reaction, finally confirming chlorophyll f’s active role in solar energy conversion.

"Far-red photosynthesis provides a new paradigm for how life can capture and use light. By combining advances in cryo-EM and computational approaches with classic spectroscopy, we resolved this long-standing mystery at the heart of the field." Professor Bill Rutherford

The study was a collaboration across 51³Ô¹ÏÍø’s Departments of Life Sciences, Physics, and Chemical Engineering, supported by the , , and , EU and , with partners from the in Austria.

Co-first author from the Department of Life Sciences said: ‘At the beginning of my PhD I would have never expected to be involved in something like this. It’s incredible what can be achieved with strong and open collaborations and great facilities. We found the chlorophyll f molecules missing from previous structural studies, and they turned out to be the in the most important places.’

A new type of photosynthesis

Far-red photosynthesis was discovered only recently, in cyanobacteria that grow in shaded environments where visible light is scarce but far-red light, which is just beyond the range of human vision, still penetrates.

In this form of photosynthesis, chlorophyll f replaces a small number of the usual chlorophyll a molecules, allowing the organisms to harvest lower-energy light.

This low-energy variant is not just a biological curiosity - it could offer a blueprint for engineering more efficient crops by extending the range of light wavelengths plants can use.

, team leader from Life Sciences, said: ‘Far-red photosynthesis provides a new paradigm for how life can capture and use light. By combining advances in cryo-EM and computational approaches with classic spectroscopy, we resolved this long-standing mystery at the heart of the field.’

The missing pigments

Previous cryo-electron microscopy (cryo-EM) models had failed to find chlorophyll f in the heart of Photosystem I, contradicting earlier biophysical evidence suggesting it played the main photochemical role.

The 51³Ô¹ÏÍø-led team used higher resolution cryo-EM, at up to 1.89 Å resolution, alongside advanced computational and spectroscopic simulations to pinpoint eight chlorophyll f molecules, including the elusive “A-1B” pigment that drives the primary electron transfer.

The team also found the other chlorophyll f molecules were grouped around the interface between the three Photosystem I complexes that make up the trimer structure, suggesting a mechanism for sharing excitation energy between monomers and improving light-harvesting efficiency.

, co-corresponding author, said: ‘Now that we have located the chlorophyll f molecules, we’re well on the way to linking each pigment’s colour, energy and function. That’s something we could never do in conventional chlorophyll a-based photosynthesis.’

A subtle structural signature

The team’s high-resolution models also revealed a previously unseen conserved structural motif that appears to stabilise the key chlorophyll f site. This motif, involving a cysteine-phenylalanine pair near the pigment, likely fine-tunes its binding and redox properties, allowing this pigment to perform photochemistry despite its lower energy.

"This discovery really highlights the power of interdisciplinary collaboration. By combining expertise from physics and life sciences we were able to apply physical science methods to biological systems and reach a coherent explanation of how far-red photosynthesis works." Professor Jenny Nelson

Earlier models had missed this because the formyl group that distinguishes chlorophyll f from chlorophyll a is almost invisible to cryo-EM, especially when not stabilised by hydrogen bonds. The combination of improved statistical methods and electrostatic simulations finally made these subtle differences detectable.

Professor Jenny Nelson, Department of Physics, said: ‘This discovery really highlights the power of interdisciplinary collaboration. By combining expertise from physics and life sciences, both at 51³Ô¹ÏÍø and with our partners in Linz, we were able to apply physical science methods to biological systems and reach a coherent explanation of how far-red photosynthesis works.’

Looking ahead

By revealing where and how chlorophyll f operates, the work provides a foundation for understanding and potentially applying far-red photosynthesis.

Professor Rutherford said: ‘As we improve our understanding of how this new form of photosynthesis works, its potential as a model for improving the efficiency of light use in crops can be explored. At the same time, it gives us a powerful comparative framework for understanding how conventional photosynthesis works – the process that powers life on Earth.’

Publication: Science, 9 October 2025
Title: “”
Authors: G. Consoli, F. Tufail, H.F. Leong, S. Viola, G.A. Davis, D. Medranda, N. Rew, M. Hofer, P. Simpson, M. Sandrin, B. Chachuat, J. Nelson, T. Renger, J.W. Murray, A. Fantuzzi, and A. William Rutherford.