LASER MICHELSON INTERFEROMETRY INVESTIGATION OF PROTEIN CRYSTAL-GROWTH

Laser Michelson interferometry was applied to study the elementary growth mechanism of protein crystals. The results for the (101) face of tetragonal lysozyme show that for supersaturations sigma higher than 1.6, growth proceeds by two-dimensional nucleation. However, at lower supersaturations growth is governed by dislocation sources. The observed non-linearity of the step velocity versus supersaturation dependence for supersaturations up to 1.2 is proved to be due to strong impurity effects. At sigma < 0.4 the crystal surface is covered with macrosteps. The effective step kinetic coefficient for the studied face is determined: beta = 2.8 x 10(-6) m/s. The applicability of general crystal growth principles and theories to protein crystallization is thus illustrated.