Based on experiments, the precise 3D structure of the protein, including hydrogen atoms, was determined, and theoretical calculations using this data visualized the electronic structure of the iron-sulfur cluster.

The researchers report that the electric potential of the iron-sulfur cluster changes dramatically depending on the presence or absence of a single hydrogen atom on an amino acid side chain, a so-called "nano-switch" mechanism.

The results not only deepen the scientific understanding of biological reactions but also provide a major clue to the future development of ultra-sensitive sensors for oxygen and nitric oxide and novel drugs.

Most reactions in living organisms involve electron transfer, which is called a redox reaction. For example, respiration and photosynthesis can be classified as redox reactions. Some proteins that assist in electron transfer contain iron and sulfur.

Ferredoxin is a small protein that contains iron-sulfur clusters and is known as the electron carrier in living organisms. Ferredoxin is a universal protein that is thought to be present in almost all living organisms; however, the mechanism by which ferredoxin stably carries electrons has remained a mystery to date.