Imaging of the crotoxin crystal in vitreous ice at 3.9 Å resolution

Abstract

The crotoxin complex is a 24,500 dalton neurotoxic protein isolated from the venom of the Brazilian rattlesnake Crotalus durissus terrificus. The crotoxin complex crystallizes as thin crystals suitable for high resolution 3-D reconstruction by electron crystallographic analysis. High resolution imaging of an untilted crotoxin complex crystal embedded in glucose has been reported. Presented here is high resolution (3.9 Å) imaging of an untilted crotoxin complex crystal embedded in vitreous ice.Several technical problems are involved in the collection of high resolution electron crystallographic data for 3-D reconstruction. First, the specimen should be as flat as possible on the grid since bending due to specimen preparation or due to beam-induced movement may cause smeared reflections in electron diffraction patterns or optical diffractograms, a phenomenon that is particularly noticeable in highly tilted specimens.