After many years, scientists are starting to understand how the chemical reactions in living cells and certain batteries produce odd and harmful forms of oxygen.

Oxygen molecules are not all the same. In some, the two highest energy electrons have opposing quantum spins, while in others, the spins are aligned. When they align, the molecule is termed “singlet oxygen.” This variant is highly reactive and can lead to harmful transformations in cellular proteins and fats, affecting some batteries too. Since the 1960s, chemists have sought to pinpoint when these perilous oxygen forms, which we normally appreciate as breathable, become problematic during chemical reactions. Stefan Freunberger from Austria and his research team at the Institute of Science and Technology have made significant progress in this area.

The team carried out various experiments starting with superoxide molecules. They studied the oxygen-dependent reactions utilized by mitochondria in energy production and its influence on the generation of both oxygen forms. While cells possess enzymes to facilitate this process, the team tested various “mediator” molecules, enabling them to observe a broader spectrum of reactions that could yield oxygen under varying energy conditions. They found that this specific energy requirement is crucial; it needs to be notably high for singlet oxygen to be produced.

“There has been considerable debate over whether singlet oxygen truly depends on the cellular environment for its formation. Up until now, this has not been clearly established,” remarked Freunberger.

Because mitochondria maintain elevated pH levels that limit their driving force, recent findings indicate that significant amounts of singlet oxygen are not generated within these cellular areas, effectively safeguarding them against damage.

Christopher McNeill from Eszürich, Switzerland, indicates that understanding singlet oxygen generation extends beyond biological implications. “Even if it forms, it can cause harm or react adversely with nearby elements,” he explains. The insights from this study could clarify certain battery types and may help elucidate why they occasionally degrade from the inside, McNeill notes.