5 - Measuring forces and manipulating single molecules

Summary

If everything seems under control, you’re just not going fast enough.

(Attributed to Mario Gabrielle Andretti, born 1940, former world champion racing car driver)

GENERAL IDEA

In this chapter we encounter the biophysical methods which can be used to measure forces exerted by single biological molecules, and also techniques which can allow us to manipulate single molecules controllably.

Introduction

There now exist several methods which permit highly controlled measurement and manipulation of the forces experienced by single biological molecules. These varied tools all come under the banner of force transduction devices, since they convert mechanical molecular forces into some form of amplified, measurable signal. They share other common features, for example, in general, the single molecules are not manipulated directly but are in effect physically conjugated, usually via one or more chemical links, to some form of adapter which is the the real force transduction element in the system. The principal forces which are used to manipulate the relevant adapter include optical, magnetic, electrical and mechanical forces, and in general all these forces are implemented in an environment of complex feedback electronics and stable, noise-minimizing microscope stages, for the purposes of both measurement and manipulation.