Microscopy Reveals Molecular Motion

Extract

Microscopes are known for demonstrating structure, but there have been many examples of how this is changing. A novel use of the atomic force microscope (AFM) by Manfred Radmacher, Monika Fritz, Helen Hansma, and Paul Hansma at the University of California, Santa Barbara, has extended the versatility of this instrument even further. They demonstrated a conformational change in a molecule that happened in a fraction of a second.

Radmacher et al. pointed out that enzymes perform their biologic function by undergoing a conformational change and that this change is within the spatial and temporal resolving capabilities of the AFM. They set out to prove this by lowering the tip of the AFM onto lysozyme, a molecule that is roughly egg-shaped, measuring about 4.5 nm by 3 nm by 3 nm. Using the tapping mode in liquid, they found that single molecules exhibited a spike-like height fluctation when in the presence of a suitable substrate.