Tables for
Volume F
Crystallography of biological macromolecules
Edited by M. G. Rossmann and E. Arnold

International Tables for Crystallography (2006). Vol. F, ch. 5.2, p. 117   | 1 | 2 |

Section 5.2.1. Introduction

E. M. Westbrooka*

aMolecular Biology Consortium, Argonne, Illinois 60439, USA
Correspondence e-mail:

5.2.1. Introduction

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Crystal-density measurements have traditionally been a valuable and accurate (±4%) method for determining molecular weights of proteins (Crick, 1957[link]; Coleman & Matthews, 1971[link]; Matthews, 1985[link]). But since exact chemical compositions of proteins being crystallized today are usually known from DNA sequences, crystal densities are rarely used for this purpose. Rather, crystal-density measurements may be necessary to define a crystal's molecular-packing arrangement, particularly when a crystal has an unusual packing density (very dense or very open); when there are a large number of subunits in the crystallographic asymmetric unit; when the structure consists of heterogeneous subunits, so the molecular symmetry or packing is uncertain; and for crystals of nucleic acids, nucleic acid/protein complexes and viruses.


Coleman, P. M. & Matthews, B. W. (1971). Symmetry, molecular weight, and crystallographic data for sweet potato β-amylase. J. Mol. Biol. 60, 163–168.
Crick, F. (1957). X-ray diffraction of protein crystals. Methods Enzymol. 4, 127–146.
Matthews, B. W. (1985). Determination of protein molecular weight, hydration, and packing from crystal density. Methods Enzymol. 114, 176–187.

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