Early in the evolution of life, cells gained the ability to perform reactions such as transferring electrons from one atom to another. These reactions, which help cells to build carbon-containing or nitrogen-containing compounds, rely on specialized enzymes with clusters of metal atoms.

By learning more about how those enzymes work, Suess hopes to eventually devise new ways to perform fundamental chemical reactions that could help capture carbon from the atmosphere or enable the development of alternative fuels.

Exploring chemistry

Suess, who grew up in Spokane, Washington, became interested in math at a young age, but ended up majoring in chemistry and English at Williams College, which he chose based on its appealing selection of courses.

I was interested in schools that were more focused on the liberal arts model, Williams being one of those. And I just thought they had the right combination of really interesting courses and freedom to take classes that you wanted he says. I went in not expecting to major in chemistry, but then I really enjoyed my chemistry classes and chemistry teachers.

I liked organic chemistry, because there’s an emphasis on making things. And I liked physical chemistry because there was an attempt to have at least a semiquantitative way of understanding the world. Physical chemistry describes some of the most important developments in science in the 20th century including quantum mechanics and its application to atoms and molecules, he says.

His project focused on molecules that consist of a metal such as iron or cobalt bound to a nonmetallic group known as a ligand. Within these molecules, the metal atom typically pulls in electrons from the ligand. However, the molecules Suess worked on were designed so that the metal would give up its own electrons to the ligand. Such molecules can be used to speed up difficult reactions that require breaking very strong bonds, like the nitrogen-nitrogen triple bond in N2.

During a postdoc at the University of California at Davis, Suess switched gears and began working on biomolecules — specifically, metalloproteins. These are protein enzymes that have metals tucked into their active sites, where they help to catalyze reactions.

Suess studied how cells synthesize the metal-containing active sites in these proteins, focusing on an enzyme called iron-iron hydrogenase. This enzyme, found mainly in anaerobic bacteria, including some that live in the human digestive tract, catalyzes reactions involving the transfer of protons and electrons. Specifically, it can combine two protons and two electrons to make H2, or can perform the reverse reaction, breaking H2 into protons and electrons.

That enzyme is really important because a lot of cellular metabolic processes either generate excess electrons or require excess electrons. If you generate excess electrons, they have to go somewhere, and one solution is to put them on protons to make H2, Suess says.

Global scale reactions

Photosynthesis, which emerged around 2.4 billion years ago, has had the biggest impact on the atmosphere, filling it with oxygen, but Suess focuses on reactions that cells began using even earlier, when the atmosphere lacked oxygen and cell metabolism could not be driven by respiration.

Many of these ancient reactions, which are still used by cells today, involve a class of metalloproteins called iron-sulfur proteins. These enzymes, which are found in all kingdoms of life, are involved in catalyzing many of the most difficult reactions that occur in cells, such as forming carbon radicals and converting nitrogen to ammonia.

To study the metalloenzymes that catalyze these reactions, Suess’s lab takes two different approaches. In one, they create synthetic versions of the proteins that may contain fewer metal atoms, which allows for greater control over the composition and shape of the protein, making them easier to study.

Source: https://news.mit.edu/2025/drawing-inspiration-ancient-chemical-reactions-daniel-suess-0320