(a) Competitive elution assay using thalidomide-immobilized beads coupled with racemic thalidomide. Beads were washed three times with 0.5% NP-40 lysis buffer and bound proteins were eluted with wash buffer containing 1 mM S-, R-thalidomide (S-Thal or R-Thal) or 0.1% DMSO for the indicated time. The eluate was then analysed by SDS-PAGE and immunoblotting (IB). (b) As in a but eluted with a buffer solution containing the indicated concentrations of S or R-thalidomide (S- or R-Thal). (c) Inhibitory effects of thalidomide enantiomers on auto-ubiquitylation of FH-CRBN were detected in the presence of MG132. Cells were treated with DMSO or the indicated concentrations of S- or R-thalidomide for 4 hours prior to harvesting.