3 Centrifugation
K. OHLENDIECK
3.1 Introduction
3.2 Basic principles of sedimentation
3.3 Types, care and safety aspects of centrifuges
3.4 Preparative centrifugation
3.5 Analytical centrifugation
3.6 Suggestions for further reading
3.1 INTRODUCTION
Biologicalcentrifugationis a process that usescentrifugal forceto separate and
purify mixtures of biological particles in a liquid medium. It is a key technique for
isolating and analysing cells, subcellular fractions, supramolecular complexes and
isolated macromolecules such as proteins or nucleic acids. The development of the
firstanalytical ultracentrifugeby Svedberg in the late 1920s and the technical
refinement of thepreparative centrifugationtechnique by Claude and colleagues in
the 1940s positioned centrifugation technology at the centre of biological and bio-
medical research for many decades. Today, centrifugation techniques represent a
critical tool for modern biochemistry and are employed in almost all invasive sub-
cellular studies. Whileanalytical centrifugationis mainly concerned with the study
of purified macromolecules or isolated supramolecular assemblies, preparative centri-
fugation methodology is devoted to the actual separation of tissues, 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
into 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. To aid in the understanding of the basic principles
of centrifugation, the general design of various rotors and separation processes is
diagrammatically represented. Often the learning process of undergraduate students is
hampered by the lack of a proper linkage between theoretical knowledge and practical
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