Binding of galactosylsphingosine (psychosine) by albumin

On applying [3H]galactosylsphingosine (psychosine) and albumin to a gel filtration column, either as a pre-incubated mixture or as separate solutions, the lipid and albumin co-eluted. When albumin and [3H]galactosylsphingosine were incubated with Sephadex G-50, the concentration of galactosylsphingosine outside the gel increased as the concentration of albumin increased. These observations indicate that albumin binds galactosylsphingosine. By using an equilibrium gel procedure, it was estimated that one molecule of albumin has 7.4 binding sites for galactosylsphingosine, and that the dissociation constant is 3.9×10−6 M. These values appear compatible with the potency of albumin to suppress galactosylsphingosine-induced hemolysis.