Nanometer Scale Motion
How do you observe motions when they are too small to see?
A microscope is typically limited to resolving spots not much smaller than about 250nm for visible light. Most people think that light microscopy is not useful for observing motions and structures of molecules. This is wrong! We use bright fluorescent semiconductor labels, quantum dots, to follow these motions. What we see are the diffraction spots from the quantum dots, just as astronomers see only diffraction spots of stars. By following the centers of gravity of the spot we can track nanometer scale motion.
We use this method to follow the motion of molecules and tissues in our studies of bone biomechanics and RNA and mRNA translation dynamics.