The transfer of protein crystals from their original mother liquor to a solution with a completely different precipitant

A procedure is described for the transfer of protein crystals form an ammonium sulfate-containing mother liquor to a solution with another precipitant, such as polyethylene glycol. The suitable concentration of the alternative precipitant is established via a novel protocol, using a hanging-drop equilibration method. This crystal transfer procedure is illustrated by experiments with crystals of trypanosomal triosephosphate isomerase and bacterial p-hydroxybenzoate hydroxylase, but it might have more general applicability. (orig.)