Yale Scientists Achieve Breakthrough in Proton Movement Measurement
Yale scientists have achieved a landmark breakthrough by directly measuring the timescale of proton movement through water molecules, setting new experimental benchmarks for a process fundamental to chemistry and biology.
Yale University researchers have, for the first time, directly measured how long it takes for protons to move through a network of six charged water molecules, marking a significant advance in understanding one of chemistry’s most fundamental processes. The findings, published September 11, 2025, by the Mark Johnson lab, provide the first experimental benchmarks for proton transfer—a process essential to phenomena ranging from vision to energy storage.
The research team, led by Professor Mark Johnson and co-lead authors Payten Harville and Abhijit Rana, used a highly specialized mass spectrometer developed over several years in Yale’s Sterling Chemistry Laboratory. This instrument, which combines precise laser pulses and cryogenic cooling, allowed the scientists to observe proton movement at an atomic scale, a feat previously considered nearly impossible due to the rapid and elusive nature of protons in water.
Unveiling the Proton Relay
Proton transfer in water, often described as a relay race where protons "jump" from one molecule to another, has been theorized for over two centuries but never directly observed or timed. The Yale team designed an organic molecule—4-aminobenzoic acid with an extra proton—attached to six water molecules, creating a controlled environment where the only path for the proton was via the water network. By monitoring changes in light absorption, the researchers could determine the proton’s starting and ending points, and crucially, the time it took to traverse the network.
"They aren't polite enough to stay in one place long enough to let us observe them easily," Johnson explained, highlighting the challenge of capturing such fleeting events. The team’s approach allowed them to set precise parameters for the beginning and end of the proton’s journey, even if the intermediate steps remained invisible.
Implications for Science and Technology
This breakthrough provides theorists with much-needed experimental data to validate and refine computational models of proton transfer, which underpin research in fields as diverse as biochemistry, materials science, and renewable energy. "We're able to provide parameters that will give theorists a well-defined target for their chemical simulations, which are ubiquitous but have been unchallenged by experimental benchmarks," Johnson noted.
The research was supported by the U.S. Department of Energy, the U.S. Air Force Office of Scientific Research, and the National Institutes of Health, underscoring its broad scientific and technological relevance. The ability to measure proton movement at this scale could inform the design of better fuel cells, batteries, and even medical diagnostics.
Years in the Making
The achievement is the culmination of years of instrument development and experimental refinement. "It took years to get the instrument to this point," said co-lead author Rana. The team’s success in measuring the rate of a chemical reaction within a finite system sets a new standard for experimental physical chemistry and opens the door to further studies of proton dynamics in increasingly complex environments.