INTRODUCTION

The biochemical analysis of subcellular structures, supramolecular complexes and isolated macromolecules is of central importance for our understanding of the molecular biology of the cell. An important prerequisite for studying the biochemical and physiological properties of organelles and biomolecules is the preservation of their biological functions and properties during the separation of cellular components. A key technique for separating and analysing the various elements of a cellular homogenate is represented by centrifugation. The development of the first analytical ultracentrifuge by Svedberg in the late 1920s and the technical refinement of the preparative centrifugation technique by Albert Claude and colleagues in the 1940s positioned centrifugation technology at the centre of biological and biomedical research for many decades. Today, centrifugation techniques are an indispensable tool of modern biochemistry and employed in almost all invasive subcellular studies. While analytical centrifugation is concerned mainly with the study of purified macromolecules or isolated supramolecular assemblies, preparative centrifugation methodology is devoted to the actual separation of cells, subcellular structures, membrane vesicles and other particles of biochemical interest.

Most undergraduate students will be exposed to preparative centrifugation protocols during practical classes and might also experience a demonstration of analytical centrifugation techniques. This chapter is accordingly divided into a short introduction to the theoretical background of sedimentation, an overview of practical aspects of using centrifuges in the biochemical laboratory, an outline of preparative centrifugation and a description of the usefulness of ultracentrifugation techniques in the biochemical characterisation of macromolecules.