PARTITION OF ADSORBED AND NONADSORBED BOVINE SERUM-ALBUMIN IN DODECANE-IN-WATER EMULSIONS CALCULATED FROM FRONT-FACE INTRINSIC FLUORESCENCEMEASUREMENTS

Front-face fluorescence spectroscopy was used to estimate directly the extent of adsorption of bovine serum albumin (BSA) onto dodecane-wate r interface in dodecane-in-buffer (pH 7.6, 0.1 M) emulsions. The wavel ength of the emission maximum (lambda(max)) of adsorbed BSA was blue-s hifted (-15 nm) as compared to that of nonadsorbed BSA in phosphate bu ffer (Castelain and Genot, 1994). The concentrations of adsorbed and n onadsorbed protein in emulsions and the partition of BSA between cream and serum were calculated from volume, oil, and protein balances and lambda(max) measured on emulsions (oil volume fraction = 0.5 and 0.16; 0.1-36 g of BSA/L aqueous phase), creams, and serums. In emulsions co ntaining 0.5 g of BSA/L, the protein was totally adsorbed at the inter face and the serum phase did not contain any protein. When the protein concentration increased, the nonadsorbed BSA concentration increased more rapidly than the adsorbed one. However, serum phase contained ads orbed proteins at concentrations which cannot be neglected.