Six aliquots of 125 ml of MyOne Streptavidin C1 Dynabeads (10 mg/ml suspension) were separated from their storage buffer and washed with twice with 50:50 methanol:water to remove potential MS contaminants. The beads were then washed with 1 Â B&W buffer. Six aliquots of 20 ml (1 nmol) of stock solution of one biotinylated target was mixed with 20, 10, 4, 2, 1 and 0.5 ml, respectively of the other biotinylated target. To these, water was added to make up the solution to a total of 40 ml. The aliquots were then made up to a volume of 80 ml by addition of 40 ml of 2 Â B&W buffer. These aliquots were then added to the aliquots of washed beads. The biotinylated targets were then incubated at room temperature with the streptavidin beads for 1 h according to the manufacturer's instructions to immobilize the targets on the beads. The target solution was then removed from the beads and the beads were washed twice with hybridization buffer.