QUANTITATIVE STUDY OF CRYSTALLIZATION KINETICS OF HEN EGG-WHITE LYSOZYME USING MAGNETIC ORIENTATION

Magnetic stabilization energy of a lysozyme crystal is a function of b oth magnetic strength and the number of molecules in a crystal. We the refore used magnetic orientation to clarify the process under normal g ravity where crystals grow in solution and then sediment to the bottom of the vessel, where they continue to grow. When a magnetic field of 1.6 T was applied immediately after the solution preparation (t = 0) a nd was continued for various duration times, photomicrographs taken af ter completion of the crystallization process showed that magnetically oriented crystals sediment before the field was switched off (t = t). The ratio of the number of magnetically orientated crystals to the to tal number of crystals could be approximated by Ratio = 1 - exp(- kt), where k is a rate constant of the crystal growth and sedimentation. W hen the supersaturation ratio beta was 5.3, 6.7, and 8.0, the approxim ated value of k was 0.016, 0.15, and 0.48h, respectively, k significan tly increases with increasing beta. This equation explains quantitativ ely the transient behavior of the growth and sedimentation of crystals . We also analyzed Ratio by growing crystals under various magnetic-fi eld strengths (0-1.6 T), and found that most crystals sediment to the bottom, when their size is 2-6 mu m Numerical simulation also showed t hat the process of sedimentation is determined by the size of crystals . In conclusion, a rate constant k that we determined in this study ch aracterizes the process where crystals grow to 2-6 mu m and then sedim ent to the bottom of the vessel, and that crystallization growth stron gly depends on the supersaturation ratio beta. (C) 1998 Elsevier Scien ce B.V. All rights reserved.