B. To selectively label intracellular HC575A, cells were treated with 1 nM Halo-tag TMR Direct Ligand for 24 hours. The left panel shows aliquots of the lysates of the indicated transfectants, resolved under non-reducing conditions and decorated with anti-λ antibodies. In the two right panels, samples were precipitated with NP-Sepharose and electrophoresed under non reducing conditions. The signal for the Halo-tag TMR was checked directly in the gel. The arrows point at the various assemblies between µ, HC575A and λ chains. 