Scanning Transmission Electron Microscopy of DNA-Protein Complexes

The scanning transmission electron microscope (STEM) at Brookhaven National Laboratorundefined (BNL) is nearly unique in its ability not only to image isolated unstained and unshadowed biological molecules but also to obtain quantitative information about them such as their oligomeric state (1 ) (see Note 1 ). This makes it ideal, in principle, for looking at protein-DNA complexes and obtaining information about the masses bound. However, there are very stringent requirements on the purity and stability of the samples.