Atomic force microscopy of viruses.

Atomic force microscopy (AFM) is a helpful tool to acquire nanometric-resolution images, and also to perform a certain physical characterization of specimens, including their stiffness and mechanical resilience. Besides of the wide range of applications, from materials science to biology, this technique works in a variety of conditions as long as the sample is supported on a solid surface, in air, ultra high vacuum or, most importantly for virus research, in liquids. The adaptability of this technique is also fostered by the variety of sizes of the specimens that it can dealt with, such as atoms, molecules, molecular complexes including viruses and cells, and the possibility to observe dynamic processes in real time. Indeed, AFM facilitates single molecule experiments enabling not only to see but also to touch the material under study (i.e., to undertake mechanical manipulations), and constitutes a fundamental source of information for material characterization. In particular, the study of the mechanical properties at the nanoscale of viruses and other biomolecular aggregates, is providing an important set of data which help to elaborate mechano-chemical structure/function models of molecular biomachines, expanding and complementing the information obtained by other structural techniques.