Enzymes² carry out fundamental biological processes such as photosynthesis³, nitrogen fixation and respiration⁴, with the help of clusters of metal atoms as "active" sites. But scientists lack basic information about their function because the states thought to be critical to their chemical abilities cannot be experimentally observed. Now, researchers at Princeton University have reported the first direct observation of the electronic states of iron-sulfur clusters, common to many enzyme¹ active sites. Published on August 31 in the journal Nature Chemistry, the states were revealed by computing⁵ the complicated quantum mechanical behavior of the electrons in the clusters.

 

"These complexes were thought of as impossible to model, due to the complexity⁶ of the quantum mechanics," said Garnet Chan, the A. Barton Hepburn Professor of Chemistry and corresponding author on the paper.

 

In these systems, the electrons interact strongly with each other, their movements resembling a complicated dance. To reduce the complexity, the researchers drew on a new understanding, gained from fundamental work in quantum information theory, that the motion of the electrons had a special pattern.

 

"At first glance, the electrons appear to move in a complicated way, but eventually you realize that they only care about what their immediate⁷ neighbors are doing, similar to being in a crowded room. This restriction⁸ on their behavior leads to important simplifications: the calculations become very difficult rather than impossible -- it's just on the edge of what can be done," Chan said.

 

Using their new method, Chan and coworkers found that iron-sulfur clusters possess an order of magnitude more accessible electronic states than previously⁹ reported. The researchers suggested that this unusual richness might explain their ubiquity in biological processes.

点击收听单词发音