Agarose gel as a medium for growing and tailoring protein crystals

The nucleation inducing ability of agarose gels has been exploited to study the crystallization of proteins in diffusion-dominated environments. The crystal size was successfully tuned in a wide range of gel, protein, and precipitant concentrations. The impact of the gel content on crystal size was independent of the specific protein, allowing the mathematical prediction of crystal size and pointing out the exclusivity of physical interactions between the gel and the protein. The versatility of the technique and the fine-tuning of the nucleation flux was demonstrated by crystallizing five different proteins and implementing batch and counter-diffusion crystallization. In addition, the potential of agarose gel to be used not only as a growth but also as a delivery medium for serial crystallography applications has been proven by preparing unidimensional microcrystal slurries with 0.1% (w/v) gel.