Force denaturation of proteins - an unfolding story

Many proteins react or respond to mechanical force as part of their function. Until recently the mechanical properties of proteins on the nanoscale were unknown as techniques that allowed their manipulation and measurement were not available. Over the last decade, development of robust instruments capable of picoNewton force sensitivity and sub-nanometre positional accuracy has allowed such experiments to be routinely undertaken. These experimental data, in conjunction with computational simulation methods and the development of an underpinning theoretical framework, have resulted in a greater understanding of the effects of a mechanical perturbation on biomolecules. The aim of this review is to describe how mechanical extension is thought to denature proteins, how this process differs to the intrinsic unfolding pathway and, by reference to examples, to rationalise the wide range of mechanical responses that have been observed, sometimes in proteins with very similar structures.