Wet-stamped precipitant gradients control the growth of protein microcrystals in an array of nanoliter wells

Wet stamping initiated from a hydrogel reservoir soaked in a salt precipitant sets-up multiple conditions for the growth of protein crystals over an array of nanoliter wells. Diffusive delivery of the precipitant translates into time- and space-varying fluxes of the precipitant in the wells. These fluxes, in turn, control the numbers of seeded crystals as well as their dimensions. Reaction-diffusion equations with a nucleation term are developed to model the process of crystal growth and to relate the 'schedules' of precipitant delivery to the dimensions and habits of the protein microcrystals in the array.