Self-assembly of β-casein and lysozyme

The self-assembly of β-casein and lysozyme, a linear and a globular protein with isoelectric point of pH 5.0 and 10.7, respectively, was studied. Polydisperse electrostatic complex micelles formed when mixing β-casein and lysozyme aqueous solutions. After the micelle solution was heated, lysozyme gelated and β-casein was trapped in the gel, producing narrowly dispersed nanoparticles. The nanoparticles were characterized with laser light scattering, ζ -potential, steady state fluorescence, atomic force microscopy, and transmission electron microscopy. The nanoparticles have spherical shape and their sizes depend on the pH of the heat treatment and the molar ratio of β-casein to lysozyme. The nanoparticles display amphoteric property and are relatively hydrophobic at pH around 5 and around 10. The net charges on the surface stabilize the nanoparticles in the solution. © 2007 Elsevier Inc. All rights reserved.