A NOVEL-APPROACH FOR THE CRYSTALLIZATION OF SOLUBLE-PROTEINS USING NONIONIC SURFACTANTS

Crystallization trials using three polyoxyethylene surfactants as prec ipitating agents are described. Of the eight soluble proteins screened , five were successfully crystallized at the first attempt. These incl uded lysozyme, catalase, ferritin, ribonuclease A and ubiquitin. Furth er work suggested that these surfactants could also be suitable for cr yo-crystallographic analysis of crystals. At the concentrations used i n the crystallization trials [10-40%(v/v)], they are capable of promot ing the formation of non-crystalline glasses at cryogenic temperatures (77 K). This would facilitate crystal mounting and allow the minimiza tion of crystal irradiation damage. Results from this study also sugge st that proteins remain stable at high concentrations of these surfact ants [40%(w/v)] and over long time periods (>1 month). A number of mem brane proteins were also screened for crystallization. These included photosystems I and II and light harvesting complexes I and II from spi nach and bacteriorhodopsin from Halobacterium halobium. The trials wer e unsuccessful both in the absence and presence of heptane-1,2,3-triol and over a wide range of surfactant concentrations.