Scientists have simulated every atom of a light-harvesting structure in a photosynthetic bacterium that generates energy for the organism. The simulated organelle behaves just like its counterpart in nature, the researchers reported in a recent publication in Cell. The work is a major step toward understanding how some biological structures convert sunlight into chemical energy, a biological innovation that is essential to life.

The team originally was led by University of Illinois physics professor Klaus Schulten, and the work continued after Schulten’s death in 2016. The study fulfills, in part, Schulten’s decades-long dream of discovering the mechanisms by which atomic-level interactions build and animate living systems.

Schulten decided very early in his career to study photosynthetic systems, said study co-author Melih Sener, a research scientist at the U. of I.’s Beckman Institute for Advanced Science and Technology, where much of the work was conducted. Schulten and Sener modeled the chromatophore, a primitive photosynthetic organelle that produces chemical energy in the form of a molecule known as ATP. That work involved a long-term collaboration with Neil Hunter from the University of Sheffield, who provided much of the experimental data.

“Schulten was a physicist; he wanted to understand biology at the physics level,” said Illinois biochemistry professor and study co-author Emad Tajkhorshid. “But then he realized biology only works if you put all of the complexity into the model. And the only way to do that was with supercomputers.”

The study confirms that, at the atomic scale, physics drives biology, the researchers said. The work will inform future studies of more complex energy-generating organelles in other microorganisms, and in plants and animals, they said. And it will advance scientists’ understanding of nature’s solution to a perpetual human problem: how to efficiently extract energy from the environment without poisoning oneself.