Macromolecular Crystals—Growth and Characterization

Abstract

This chapter reviews the techniques used to characterize macromolecular crystals. It discusses the relationship between the growth conditions and the crystal quality. The macromolecular crystals are grown according to the classical crystal growth mechanisms. They contain all the crystalline defects found in crystals of small molecules. Biological macromolecules such as proteins, carbohydrates, nucleic acids and viruses form crystals. The crystallization of these large molecules takes place by the same mechanisms that account for the growth of crystals of small molecules, namely normal growth and tangential growth either by two-dimensional nucleation or by screw dislocation. Macromolecules form crystals through intermolecular contacts driven by unspecific attractive interactions that are stabilized by hydrogen bonding, hydrophobic interactions, ion pairing, and other weak forces. One of the main differences between the macromolecular crystals and the crystals of small molecules is the role of water in preserving their crystalline order. Water molecules help to maintain the crystal structure of the macromolecular crystals, and sometimes account for more then 60% of the crystal mass. Thus, the characterization of the macromolecular crystals is possible only with techniques that do not require an environment for sample preparation or observation that provokes water evaporation.