Exploring Folding Pathways of Single Proteins Using Mechanical Manipulation

Protein folding is still a major area of active research. Despite significant progress in understanding the underlying principles, we still cannot efficiently predict the folding mechanism for even a moderately sized protein. Proteins are generally thought to fold by diffusion over a three-dimensional energy landscape. Traditional bulk methods have proven to be very powerful in the study of the folding process but they often suffer from inherent ensemble averaging. Single molecule techniques open up new vistas for studying protein folding, allowing direct analysis of the distribution of events that characterize the heterogeneous folding process. Recently it has become possible to directly manipulate individual proteins using optical tweezers. Here we illustrate the experimental strategy and how this approach has provided a fresh perspective on the protein folding problem.