The technique of X-ray crystallography, essential to our attempts at structure-assisted vaccine design, is dependent on the relatively poorly understood process of protein crystallization. A central stumbling block in our investigations of the HIV-1 envelope has been the difficulty in obtaining well-diffracting crystals. To solve this problem, we have focused on the development of methods to enhance the probability of crystallization. These have ranged from developing novel crystallization screens, to examining the effect of precipitant point optimization on crystallization frequency, to combining variational crystallization with robotic liquid handling techniques. These methodological improvements have proven critical to the crystallization of HIV-1 envelope:antibody complexes, especially for complexes containing the flexibly, highly glycosylated, gp120 envelope glycoprotein.
