A NEW ADDITIVE FOR PROTEIN CRYSTALLIZATION

The potential usefulness of the new zwitterionic solubilizing agent, d imethyl ethylammonium propane sulfonate (NDSB195), in protein crystall ization was shown using hen egg-white lysozyme. In the presence of thi s agent, highly diffracting crystals were obtained using ammonium sulp hate as a precipitant, whereas in its absence only amorphous precipita tes were obtained. The crystals possess a triclinic unit cell not prev iously described and diffract to a resolution of 2 Angstrom. To ascert ain that the new reagent had not produced significant changes in the p rotein fold the structure was determined to a resolution of 2.6 Angstr om. Only minor differences were observed (notably in regions of crysta l contacts) with the known tetragonal lysozyme structure (Brookhaven P rotein Data Bank entry 1HEL).