ABSTRACT
In principle, the crystallization of a protein, nucleic acid, or virus is a little different than the crystallization of conventional small molecules. The greater difficulties that arise in the crystallization of macromolecules in comparison with conventional small molecules stem from the greater complexity, lability, and dynamic properties of proteins and nucleic acids. Certain properties of proteins render the problem of crystallization particularly difficult to treat systematically or in strictly analytical terms. Macromolecular crystals are by comparison usually much more limited in size, are very soft and crush easily, disintegrate if allowed to dehydrate, exhibit weak optical properties, and diffract X-rays poorly. Macromolecular crystals are temperature sensitive and undergo extensive damage after prolonged exposure to radiation. A macromolecule may be guided gradually toward crystallization by dialysis against a solution of salt or organic solvent concentration nearly adequate to produce precipitation. A means for limiting nonspecific aggregation is the inclusion of mild, usually nonionic, detergents in the crystallization mother liquor.
