Living quantum engines

All known oxygen-breathing life processes energy using a series of membrane-bound structures called the cellular respiratory chain (or "electron transport chain"). This system is essentially a chain of electric motors, powered by just a few tunneling electrons. Thanks to the advent of powerful experimental and numerical techniques, biological molecules have become a particularly attractive medium in which to study quantum transport. The bacterium Paracoccus denitrificans is believed to share a common ancestor with the modern mitochondrion (the "powerhouse of the cell"). I present my work on the characterization of a single tunneling step in the respiratory chain of Paracoccus denitrificans. This research is motivated by a recent experiment in which anomalous electron transfer rates were measured for this tunneling step [Biochemistry 46, 11137 (2007)]. I discuss ways in which specific amino acids may enhance the tunneling rate at the electron transfer interface, and the methods my collaborators and I are using to "get to the bottom of things."