Use of the Airfuge for analysis and preparation of receptors incorporated into liposomes: Studies with the receptor for immunoglobulin E

A Beckman Airfuge has been employed for studying the interaction between lipids and the receptor for immunoglobulin E (IgE). For analytic experiments, samples were applied underneath a discontinuous sucrose gradient. After a 30-min centrifugation in a fixed-angle rotor, liposomes floated toward the top of the gradient whereas unincorporated receptor-IgE complexes remained at the bottom of the tube. Liposomes with incorporated receptors were also efficiently separated in the ACR-90 preparative rotor. These methods of "Airfuge flotation" can provide useful adjuncts to more traditional methods for density-gradient centrifugation especially when rapid analysis of small samples is desired.