Abstract
The interaction between β- and κ-casein-like fractions of human milk was studied by analytical ultracentrifugation and difference spectrophotometry. The mixture of human β- and κ-casein-like fractions was stabilized against precipitation by calcium. In the ultracentrifugal analysis, the sedimentation coefficient of the fast peak of the β-casein-like fraction was s20, ω=14.7 S and that of the κ-casein-like fraction was s20, ω=19.5 S. When both caseins were mixed with the ratio of 1 : 1 or 2 : 1, a new peak of 17 S was observed at 25°C.The change in difference spectrum of the mixture was larger than that in the case of each solution alone, and agreed with that of human whole casein between the temperatures of 10 and 25°C These results seemed to show that β- and κ-casein-like fractions interact at 25°C.
