September 23, 2019
What Is a Single Molecule, and What Can You Do With It?
A single molecule is ridiculously tiny, about 1 nanometer, roughly 100,000 times smaller than the diameter of a human hair. Yet individual molecules rule the nanoscale activity and structure in our cells. Thirty years ago, single molecules were first detected optically, but how do we really detect a single molecule today, and what good is it? It is an amazing fact that you can even detect single molecules with your own eyes. When a new regime of science is breached, surprises often occur: single molecules show amazing dynamics, blink on and off, and can be controlled by light. Far from being only an esoteric effect, these “switching properties” of molecules can now be used to obtain “super-resolution” to see the tiny nanoscale structures inside cells. Essentially, with tiny single-molecule light sources decorating a structure, the on/off process is used to light up only subsets at a time, and a pointillist reconstruction reveals the hidden nanometer-scale structure, opening up a new frontier for understanding and applications. And if we watch single molecules moving around, we learn about details of local environments and time-dependent changes inside cells.
September 24, 2019
Providing 3D for Super-Resolution Microscopy and Single-Particle Tracking in Cells with Single Molecules
Super-resolution microscopy has opened up a new frontier in which biological structures and behavior can be observed in fixed and live cells with resolutions down to 20-40 nm and below. Examples range from protein superstructures in bacteria to bands in axons to details of the shapes of amyloid fibrils, cell surface sugars, and much more. Current methods development research addresses ways to extract more information from each single molecule such as 3D position and orientation, and to assure not only precision, but also accuracy. Low temperature single-molecule imaging can be combined with cryo-electron microscopy, too. Still, it is worth noting that in spite of all the interest in super-resolution microscopy of extended structures, even in the “conventional” single-molecule tracking regime where the motions of individual biomolecules are recorded in cellular environments, much can be learned. Combining super-resolution imaging of a static structure with 3D tracking of other biomolecules provides a powerful view of cellular dynamics.
William Esco Moerner (born June 24, 1953) is an American physical chemist and chemical physicist with current work in the biophysics and imaging of single molecules. He is credited with achieving the first optical detection and spectroscopy of a single molecule in condensed phases, along with his postdoc, Lothar Kador. Optical study of single molecules has subsequently become a widely used single-molecule experiment in chemistry, physics and biology. In 2014, he was awarded the Nobel Prize in Chemistry.