CONTAMINANT EFFECTS ON PROTEIN CRYSTAL MORPHOLOGY IN DIFFERENT GROWTHENVIRONMENTS

Contaminant effects on the morphology of turkey egg-white lysozyme (TE WL) crystals grown in ungelled and in gelled growth media have been in vestigated. The latter may serve as a model system for future microgra vity experiments. Hen egg-white lysozyme (HEWL) was added as the conta minant at levels ranging from 4 up to 70%(w/w) (total protein). Morpho logy measurements indicate a contaminant effect leading to a shortenin g along the c axis of the crystal. This shortening effect depends on t he contaminant concentration. It is attenuated and varies more regular ly in gelled than in ungelled growth media. The specificity of the HEW L contaminant effect was verified by addition of ribonuclease A, which did not influence crystal morphology. Contaminant inclusion into the growing TEWL crystals could be calculated directly from equilibrium pr otein concentration measurements. The level of HEWL inclusion is close ly related to the concentration of HEWL in the growth solutions. The s pecificity of the observed effect as well as the differences between t he two growth media are discussed.