Single particle macromolecular structure determination via electron microscopy

Three-dimensional structure determination of macromolecules and macromolecu lar complexes is an integral part of understanding biological functions. Fo r large protein and macromolecular complexes structure determination is oft en performed using electron cryomicroscopy where projection images of indiv idual macromolecular complexes are combined to produce a three-dimensional reconstruction. Single particle methods have been devised to perform this s tructure determination for macromolecular complexes with little or no under lying symmetry. These computational methods generally involve an iterative process of aligning unique views of the macromolecular images followed by d etermination of the angular components that define those views. In this rev iew, this structure determination process is described with the aim of clar ifying a seemingly complex structural method. (C) 2001 Federation of Europe an Biochemical Societies. Published by Elsevier Science B.V. All rights res erved.