Methods to efficiently determine the phase behavior of novel proteins have the potential to significantly benefit structural biology efforts. Here, we present protocols to determine both the solubility boundary and the supersolubility boundary for protein/precipitant systems using an evaporation-based crystallization platform. This strategy takes advantage of the well-defined rates of evaporation that occur in this platform to determine the state of the droplet at any point in time without relying on an equilibrium-based end point. The dynamic nature of this method efficiently traverses phase space along a known path, such that a solubility diagram can be mapped out for both soluble and membrane proteins while using a smaller amount of protein than what is typically used in optimization screens. Furthermore, a variation on this method can be used to decouple crystal nucleation and growth events, so fewer and larger crystals can be obtained within a given droplet. The latter protocol can be used to rescue a crystallization trial where showers of tiny crystals were observed. We validated both of the protocols to determine the phase behavior and the protocol to optimize crystal quality using the soluble proteins lysozyme and ribonuclease A as well as the membrane protein bacteriorhodopsin.
[1]
G. G. Stokes.
"J."
,
1890,
The New Yale Book of Quotations.
[2]
J. Gilman,et al.
Nanotechnology
,
2001
.
[3]
J. Luft,et al.
[7] Kinetic aspects of macromolecular crystallization.
,
1997,
Methods in enzymology.
[4]
A. McPherson.
Crystallization of Biological Macromolecules
,
1999
.
[5]
宁北芳,et al.
疟原虫var基因转换速率变化导致抗原变异[英]/Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A
,
2005
.