Removal of SDS from proteins for immunochemical analyses: a simple method utilizing ultracentrifugation in sucrose density gradients containing non-ionic detergent.

A simple method for removal of SDS from proteins is described. SDS-treated proteins are centrifuged through sucrose density gradients containing Triton X-100. Proteins possessing sedimentation coefficients of > 4 S separate from the bulk of SDS, which remains at the top of the sucrose gradients. Quantitative immunoelectrophoretic analyses of SDS-treated human serum proteins and human erythrocyte membrane proteins indicate that the majority of the proteins tested is subsequently precipitable with specific antisera. Initial membrane solubilization with SDS can thus be followed up by a fractionation step that will yield many proteins in a state immediately suitable for bioimmunochemical analyses.