Abstract
It was indicated from fluorescence spectra and fluorescence titration that a hydrophobic probe, 1-anilino-8-naphthalenesulfonate (ANS), binds to casein components (αs-, β- and κ-casein). Fluorescence intensity and affinity of ANS- κ-casein complex were larger than that of ANS- αs- and ANS-β-casein complexes. Enhancements of fluorescence intensity of complexes of casein components were observed by the addition of KCI or CaCl2. Reason for the enhancement was postulated to be the increase of the quantum yield of the ANS fluorescence caused by the environmental change of ANS binding region of the casein components.
Marked increase of sedimentation coefficient of β-casein in the presence of KCI or CaCl2 at 10°C was caused by the addition of ANS. This may be responsible for the stimulation of the Ca-dependent precipitation of β-casein by the addition of ANS.
It was found that αs•κ-association was prevented by ANS and that hydrophobic interaction have an important role for αs•κ-association.
