Verification of McCabe's ΔL Law for Growth of Lysozyme Crystals by Hanging Drop Method

Abstract

Lysozyme is a naturally occurring enzyme in egg white and has high commercial importance due to its antimicrobial properties. The main objective of this work was to study the growth rate of lysozyme crystals isolated from egg for the first 72 hours and verify the results with McCabe's constant crystal growth theory. The separation of lysozyme was carried out by adsorption onto a cationic Amberlite resin using phosphate buffer at pH 4.8. Hanging drop crystallization method was used to form high purity lysozyme crystals from the embryonic stage. To this end, this work differs from an earlier work of Forsythe et al., who used seed crystals in the size range of 10 lm-40 lm for face growth measurements at different pH values. The maximum crystal size recorded in the present work was 392.86 lm, which is within the typical size range of 50 lm-500 lm for which constant crystal growth is expected to hold according to McCabe's DL law. Electron micrographs (SEM) revealed the structure and dimensions of the crystals while SDS-Page was used to measure the purity of the crystals. The SEM results showed that lysozyme growth rate was linear and agreed with McCabe's constant growth theory, producing a growth rate of 1.77 Â 10 À3 mm Á s À1 .