Purification of DPS from E. coli. (a) DPS is a homododecamer of 20 kDa peptides. The Coomassie-stained denaturing gel shows DPS as purified after ion-exchange chromatography. Lane M contains molecular-weight markers (labelled in kDa). (b) Representative micrograph (100 kV, cropped from full frame) of DPS particles in unsupported vitreous ice.