Macromolecular assemblies: greater than their parts

Increasingly powerful methods of analysis have opened up complex macromolec ular assemblies to scrutiny at atomic detail. They reveal not only examples of assembly from preformed and prefolded components, but also examples in which the act of assembly drives changes to the components. In the most ext reme of these examples, some of the components only achieve a folded state when the complex is formed. Striking results have appeared for systems rang ing from the already mature field of virus structure and assembly, where no table progress has been made for rather complex capsids, to descriptions of ribosome structures in atomic detail, where recent results have emerged at breathtaking speed.