Functional Changes in β-Lactoglobulin upon Conjugation with Carboxymethyl Cyclodextrin

Bovine beta-lactoglobulin-carboxymethyl cyclodextrin (beta-LG-CMCyD) conjugate was prepared using water-soluble carbodiimide, in an effort to improve the functional properties of the protein. The molar ratio of beta-LG to CMCyD in the conjugate was 1:2. The isoelectric point of the conjugate was 4.1-5.8. Spectroscopic studies indicated that the global conformation of the conjugate was similar to that of native beta-LG. Structural analyses with monoclonal antibodies indicated that there was a conformational change around (15)Val-(29)Ile (beta-sheet). The denaturation temperature of the conjugate was about 77 degrees C, which is about 4 degrees C higher than that of native beta-LG. The beta-LG-CMCyD conjugate maintained retinol-binding activity as strong as that of beta-LG. The emulsifying activity of beta-LG was much improved and the antioxidative activity of beta-LG was maintained after conjugation with CMCyD.