溶菌酶中等电点检测方案(激光粒度仪)

ADS-SZ-ZE-004ANano Particle AnalyzernanoparticaNANO PARTICLE ANALYZERSZ-100Applications Data SheetHORIBAC 2011 HORIBA， Ltd. All rights reserved. Isoelectric Point Measurement of Lysozyme Lysozyme is an enzyme which can be foundin egg albumen as well as in tears， salivaand other secreting fluids； it serves toprotect eggs， eyes and mouth frommicroorganism infection. Commercially， it isextracted from egg albumen for use in fooditems alnd medical supplies.Included among its physical properties are amolecular weight of 14，307， an isoelectricpoint of 11.1-11.4， an optimum pH of closeto 5 and an optimum temperature of 50degree C (Fig.1). Fig.1 Tertiary structure of lysozymeSource： Free encyclopedia "Wikipedia"(2011/8/21) Method Analyzer： SZ-100 Temperature： 25.0 degree C Sample： Lysozyme， 100 mg/mL， pH 3.8 Disperse medium： Pure water Results The lysozyme sample was prepared using pure water. With an optional pH controllerconnected to the SZ-100， sodium hydroxide was added dropwise to the sample to adjust thepH value， and the zeta potential at each pH was measured. The zeta potential at each pH isshown in Table 1. Fig. 2 illustrates a trend graph which plots the zeta potential as a function ofpH. From this graph it is obvious that the isoelectric point is pH 11.4. pH Zeta PotentialmV) 3.8 16.3 5.0 8.8 6.0 6.8 7.0 7.6 8.0 7.9 9.0 6.7 10.0 6.7 11.0 2.1 12.0 -10.6 12.8 -9.8 Fig. 2 Dependence of zeta potential on pH Table 1 Zeta potential at each pH Conclusion The isoelectric point of lysozyme (which is a protein) was measured. The value obtained coincides well with the one reported in literature. Lysozyme is a form of enzyme that catalyzes the hydrolysis of polysaccharides in vivo. While in vivo, this protein is denatured by changes in temperature and pH, either varying or losing its liveliness. Measuring its dependence on these two parameters thus provides valuable information for the study of enzymatic reactions.