The findings challenge decades of scientific assumptions and provide new insights into fundamental biological processes.
Scientists have discovered that carbon monoxide (CO) separates from haemoglobin through at least two distinct steps, overturning the long-held belief that this process occurs in a single event.
Haemoglobin discovery challenges assumptions
The research, published in Nature Communications, represents the first direct experimental evidence of multiple pathways in how CO detaches from haemoglobin.
The discovery is particularly significant because haemoglobin is one of the most important proteins in nature and serves as the key constituent of blood.
Haemoglobin is responsible for delivering oxygen throughout the body but it is also what CO binds to during carbon monoxide poisoning.
This makes CO dangerous as it prevents oxygen transport.
Advanced laser technology reveals
The breakthrough was made possible through advanced spectroscopic techniques available at the Central Laser Facility, operated by the Science and Technology Facilities Council (STFC).
Researchers investigated the CO-haemoglobin bond breaking process called photodissociation by using laser pulses to separate carbon monoxide and studying the resulting processes.
The team identified a previously unknown slower separation step that occurs approximately 15 picoseconds after the well-documented ultra-fast separation, which happens in under 50 femtoseconds.
An additional pathway
To put these timescales in perspective, there are more femtoseconds in one second than there are seconds in 32 million years.
A picosecond is still unimaginably fast to humans, but it is 1,000 times slower than a femtosecond.
Instead of CO simply being removed all at once, researchers discovered there are two separate events.
This includes an additional pathway for bond breaking between the iron atom of haemoglobin and the small molecule it carries.
Future research implications
This finding resolves an ongoing scientific debate about the mechanism of CO photodissociation from haeme iron.
It also offers new insights into protein dynamics, a critical factor in understanding how proteins function in living systems.
Such bond breaking and formation forms the basis for respiration and serves as the key trigger of important reactions in biology, including:
- protein conformational changes
- cellular signalling
- electron transfer
Subject of scientific curiosity
Dr Igor Sazanovich explains the significance:
This discovery advances our understanding of the key fundamental process in chemistry and biology, which is bond breaking and formation between ligands and proteins.
This work will help other researchers to better understand how biological processes work and how proteins work, so that they can design new medicines and find new ways to treat diseases.
Although haemoglobin has been the subject of scientific curiosity for many years, it was not previously possible to observe these details.
It requires a unique laser instrument capable of measuring infrared light with superior sensitivity and time resolution.
Collaborative research excellence
The research was conducted by scientists from:
- the Central Laser Facility operated by the STFC
- the Institute of Physics and Institute of Bioorganic Chemistry in Minsk
- the University of Sheffield
This work demonstrates the unique experimental capabilities and expertise provided by the Central Laser Facility to the scientific community in the UK and worldwide to facilitate world-class research and innovation.
The work provides researchers with better knowledge of how biological processes and proteins function.
Help make more informed decisions
This improved understanding could help scientists make more informed decisions when designing new treatments or finding new approaches to address diseases.
However, this research represents fundamental science rather than direct medical applications.
The paper was published in Nature Communications on 20 August 2025.