Studies of Microtubule Intracellular Highways: Building Bridges between Physics and Biology
Because it wasn't discovered until the 1960s, it's still news to some people that the cells of animals and plants have a sort of skeleton—biologists call it a "cytoskeleton"—composed of a network of protein filaments, much like the bones inside a person. Scientists call the tiny protein filaments that make up the cell's bones "microtubules" because they are hollow tubes that are micrometers in length. That's amazing enough, but Cottrell Scholar Jennifer Ross is studying microtubules because we have since learned they play a role much like that of a "smart" railroad or roadway in transporting —"translocating" in biospeak—organelles, useful proteins and other cargo around the cell's interior. These items are moved along by "motor proteins" powered by adenosine triphosphate (ATP), the energy source of the cell. Previous studies have examined one motor protein "walking" on one microtubule, but the cell is more complicated and crowded that that. As a physicist, Ross is using her Cottrell Award to focus on how bundles of microtubules affect motility within the cell under more "real-world" conditions. Using the tools of molecular biology and biochemistry, she will construct a variety of roadway types and explore their behavior with a number of different "motor assemblies." Ross has built a special type of microscope to image single motors and associated proteins bound to microtubules during these experiments. The "single molecule total internal reflection fluorescence microscope," as the name implies, can look at single molecules inside live cells. She will use "optical tweezers," or beams of light, much like a tractor beam on Star Trek, to manipulate and measure the forces of the tiny motors. If successful, her experiments may be the first systematic study of how the architecture of microtubule networks controls molecular motor transport.
"Optics is an applied sub-field of physics that life science researchers employ daily," Ross says. "To bridge the gap and educate more life science students in the field of physics, I've developed a new course called ‘Optics for Biophysics,' an interdisciplinary course engaging students from physics, chemistry, life science, and engineering." She says the lecture portion of the course seeks to educate all participants in advanced mathematics and physics, focusing especially on helping the life science students to understand these theoretical methods. In the laboratory section, the students design and build a fluorescence microscope, using the theory learned in the lecture. With the Cottrell Scholars Fellowship, Ross has been able to purchase the equipment needed for the students to build novel microscopes to address a biological question.