Application of Polarization of Fluorescence Technique to Protein Studies. III. The Interaction of κ-Casein and β-Lactoglobulin

Open Access
Publisher Website
Google Scholar
Abstract
The polarization of fluorescence technic was applied to a study of the heat induced interaction between K-casein and [beta]-lactoglobulin by determining changes in molecular rotational properties. When a mixture of the fluorescent [beta]-lactoglobulin and nonfluorescent K-casein was held in phosphate buffer for 1 hr. at 25 C and 65 C, the average apparent molecular volume of the former increased approximately 42.5 % and 96%. The mole fraction of [beta]-lactoglobulin in the complex form was most highly dependent upon the weight ratio of [beta]-lactoglobulin to K-casein (r) in the region where (r) is 1.0 or less. With fluorescent K-casein and non-fluorescent [beta]-lactoglobulin the interaction of these proteins occurs in a manner that permits the [beta]-lactoglobulin molecules to attach themselves at the K-casein micelle-water interface to produce a complex whose properties are less temperature dependent than those of pure K-casein.