Figure 1: Serum protein electrophoresis: (a) Gel picture, showing two distinct M-bands (M1 and M2); (b) Densitometric tracing, showing two M-spikes (M1 and M2); (c) Gel picture after repeat testing the serum pretreated with β-mercaptoethanol, showing a single M-band; and (d) densitometric tracing after repeat testing the serum pretreated with β-mercaptoethanol, showing a single M-spike