Free-falling crystals: Biological macromolecular crystal growth studies in low earth orbit

Spacecraft orbiting the earth experience a reduced acceleration environment due to being in a state of continuous free-fall. This state colloquially termed microgravity, has produced improved X-ray diffraction quality crystals of biological macromolecules. Improvements in X-ray diffraction resolution (or detail) or signal to noise, provide greater detail in the three-dimensional molecular structure providing information about the molecule, how it works, how to improve its function or how to impede it. Greater molecular detail obtained by crystallization in microgravity, has important implications for structural biology. In this paper we examine the theories behind macromolecule crystal quality improvement in microgravity using results obtained from studies with the model protein, chicken egg white lysozyme.