VeraCode™ beads are 240 × 28 μm, holographically encoded, glass micro-cylinders with a carboxylated surface chemistry. First, 10,000 to 40,000 VeraCode™ beads were washed 3 × 800 μL with MES Buffer (0.1 M MES, pH 4.7, 0.9% NaCl) by sequential
mixing, pelleting the beads by brief and gentle spinning (or allowing beads to settle by gravity) and removing the supernatant (wash buffer) by manual pipetting, being careful not to lose the bead pellet. All washes were performed in this manner unless otherwise indicated. After discarding the final wash, 200 μL of Sulfo-NHS Buffer (1 mg/mL in MES Buffer; prepared immediately prior to use) was added to each washed bead pellet. Beads were mixed immediately and buy Thiazovivin briefly. 200 μL of EDC Buffer (1 mg/mL in MES Buffer; prepared immediately prior to use) PD0325901 was immediately added to each sample (containing both beads and Sulfo-NHS Buffer) and immediately mixed to combine. Following incubation for 1 h with mixing (all extended mixing steps for VeraCode™ beads were done at 1200 rpm on a VorTemp 56 shaker, Labnet International Inc., Edison, NJ), the beads were then washed 3 × 800 μL briefly with MES Buffer and then 1 × 800 μL quickly with 1 × PBS (for proteins or antibodies prepared in MES Buffer, this PBS wash was omitted). The protein coupling reaction immediately followed, in which 10–40 μg of the
previously prepared recombinant protein or 100 μg of antibody was added to the beads, mixed, and incubated for 1 h with mixing (a comprehensive titration analysis was not performed due to the wide range of protein classes and wide range of concentrations at which they were supplied by the manufacturers, however, the amounts added are believed to be sufficient to saturate the bead surface, as using a calculation of 2.5 mg/m2 binding capacity of a solid non-porous surface as reported for avidin and 15 mg/m2 for antibodies (Plant et al., 1991), we estimate that 40,000 beads can bind a maximum of roughly 2–10 μg). Beads were then spun
down, and the protein solution was removed. The beads were washed 2 × 800 μL briefly with BSA Block (1% BSA [w/v] in TBS-T; TBS = 50 mM Tris, pH 7.5, 200 mM NaCl; TBS-T contains 0.05% [v/v] Tween-20) before discarding the wash and incubation with an additional 400 μL of BSA Block for 30 min. N-acetylglucosamine-1-phosphate transferase Beads were then washed briefly 1 × with 800 μL of PBS-1 M NaCl, 1 × 30 min with 400 μL of PBS-1 M NaCl (with shaking) and then 2 times briefly with 800 μL TBS-T. Beads were stored in TBS-T at 4 °C. For optimal performance, we used an indirect method of coating VeraCode™ beads with biotin followed by streptavidin. Streptavidin beads were then used to in situ capture/purify cell-free produced proteins carrying the SBP-Tag (Keefe et al., 2001), directly from the crude expression reaction. First, a vial of 20,000 carboxyl-terminated VeraCode™ beads was washed 5 × 400 μL with MES Buffer (0.1 M MES, pH 4.7, 0.9% NaCl).