Grant J. Jensen PhD

Dr. Grant Jensen is a structural biologist at the California Institute of Technology who believes that seeing can be the fastest path to believing. Seeing brings bursts of understanding at a single glance, even though those glances can sometimes be extraordinarily difficult to obtain. Jensen works at the front edge of an emerging microscope technology called electron cryotomography (ECT). ECT combines an electron microscope beam, a cryogenic plunge freezing to fix the sample, and a motor-driven stage to tilt it, one degree at a time, through two axes while a charge-coupled device (CCD) camera reels off still shots of the sample. This river of images and positional data flow to a tomographic computer program, which merges it all and calculates three-dimensional models. With those, Jensen makes moving pictures of things once invisible.

Take, for example, the stator, or an anchored portion, of the bacterial flagellar motor. Flagellar motors are a great natural wonder of biology: self-assembling nanomachines that spin whip-like flagella, propelling bacteria like speedboats. Over the past 30 years, molecular biologists have labored to deconstruct the flagellar motor into its constituent parts and evolutionary origins. Yet no one had ever seen the stator, the part that holds the motor in place on the cell, in molecular detail. A flagellar motor is like an electric drill, except it spins, not a drill bit, but the flagellum, Jensen explains. But somebody has to hold the drill for it to work. Likewise, something has to hold the flagellar motor for it to spin the flagellum effectively. That's the stator. In previous attempts to study the motor, researchers had been unable to see the stator, since it was left behind, stuck to the cell.