LONG-TERM STUDIES ON TETRAGONAL LYSOZYME CRYSTALS GROWN IN QUIESCENT AND FORCED-CONVECTION ENVIRONMENTS

The growth of tetragonal hen lysozyme crystals in the size range 150-3 00 mu m was studied using digital microscopy; the size and orientation of the growing crystals were estimated from the geometry of the ideal tetragonal lysozyme crystal. At a confidence level above 99%, statist ical analyses indicate the (110) face growth rates of crystals grown i n quiescent conditions are not inhibited by weak buoyancy-driven natur al convection. Yet similar analyses of crystals subjected to a weak fo rced flow of the same magnitude indicate a statistically significant d ecrease in growth rate with time. This apparent paradox probably resul ts from mass transport limitations within the crystal growth cell. Mat hematical models of fluid mixing inside the growth chamber suggest tha t crystal growth is limited by the rate at which protein molecules are transported to crystals growing on the walls of the chamber. Our expe riments also reveal a large variation in the growth rates of crystals within a nominally homogeneous population. The local environment of th e crystal may account for some of the variation, but the mechanisms ar e not understood.