IN-SITU STUDIES OF PROTEIN CRYSTAL-GROWTH BY ATOMIC-FORCE MICROSCOPY

Atomic force microscopy was used to obtain images of lysozyme crystals growing in their native solution environment. We observed growth by b oth two-dimensional nucleation and screw dislocation mechanisms. Nucle ation centres appeared to occur randomly over the surface, and were un correlated from layer to layer. Surface defects on the (110) face were found in the form of double-arm spirals, opposing pairs of such spira ls, or more complex structures. The formation of defects as layers gre w over foreign particles, and occasional later healing of the defects, were followed. At sufficiently low supersaturation, defect-mediated g rowth dominated over growth by two-dimensional nucleation.