Watching Protons Move in Chemical Reactions

New study provides direct evidence of proton transfer at the molecular level.

The Science

The transfer of protons has been widely regarded as a key step in many electrochemical and biological processes. But scientists have never had direct molecular evidence of how these positively charged particles move. Now an international team of scientists has examined the transfer of protons as acetaminophen breaks down at the molecular level. Their work is building a fundamental understanding of the proton transfer process and provides the direct molecular evidence that has been lacking for so long.

The Impact

The transfer of protons plays an important role in chemical and biological processes, especially when water is involved. In biology, the transport and storage of protons form the basis for how our bodies use energy. Protons also affect how our enzymes function. A better understanding of how protons move in chemical reactions enables the development of new bioproducts such as environmentally friendly biochemicals and renewable energy sources.


Scientists at the East China University of Science and Technology, China’s National Centre for Mass Spectrometry, and the Chinese Academy of Sciences teamed with their counterparts at EMSL, the Environmental Molecular Sciences Laboratory, a U.S. Department of Energy Office of Science user facility, to find a way to directly observe proton transfer. They faced challenges because proton transfer is fast and takes place in a confined space on the nanometer scale, making it impossible for traditional analysis tools to measure. By coupling a specially designed analysis cell with EMSL’s time-of-flight secondary ion mass spectrometry, they were able to directly examine the release and recombination of protons as acetaminophen dissolved in water. Their observations marked direct evidence of the process at the molecular level. Computer simulations mirrored their observations. The work offered the most comprehensive understanding of the complex chemistries involved to date and was featured on the cover of The Journal of Physical Chemistry Letters.

Principal Investigator(s)

Zihua Zhu
Environmental Molecular Sciences Laboratory


This work was supported by the U.S. Department of Energy’s Office of Science, Office of Biological and Environmental Research, including support of the Environmental Molecular Sciences Laboratory (EMSL), a DOE Office of Science User Facility; Open Call Laboratory-Directed Research and Development funds from Pacific Northwest National Laboratory; the National Natural Science Foundation of China; and the China Scholarship Council.


Wang, J.-G., Y. Zhang, X. Yu, X. Hua, F. Wang, Y.-T. Long, and Z. Zhu. “Direct molecular evidence of proton transfer and mass dynamics at the electrode-electrolyte interface.” The Journal of Physical Chemistry Letters 10(2), 251-258 (2019). [DOI:10.1021/acs.jpclett.8b03282]