Sino Biologicals 40143-MM08 was first buffer exchanged into PBS to remove any interfering substances using Amicon filters (Sigma, St Louis, MO, 50 kDa MWCO, UFC5050). Specifically, the antibody was concentrated 20-fold and brought back to the original volume with PBS. This was done three times to remove sodium azide. The antibody was biotinylated at 1.5 mg/mL with 50 molar excess NHS-dPEG₁₂-biotin (10198, Quanta Biodesign, Plain City, OH, USA). Excess biotin was removed using Amicon filters again, this time with five total concentration and resuspension cycles. The concentration of the biotinylated antibody was determined using the A280. The final biotinylation molar ratio was determined to be 20 moles of biotin per mole of antibody using the QuantTag Biotin Quantification Kit (BDK-2000, Vector Laboratories, UK). If supply or cost constraints limit the utility of the above antibodies, our previously reported antibody screening effort may be used to select alternates.