Amicon ultra 0.5 ml centrifugal filters ultracel 50 k regenerated cellulose 50000 nmwl

To antibody in 0.1 mol · L⁻¹ HEPES at pH 8.5, 10 µL of DFO in dimtethyl sulfoxide (233.3 µmol · L⁻¹) was added three times followed by mixing to a final DFO:antibody ratio of 7:1. The reaction was mixed at room tempterature for 30–60 min. Excess unreacted DFO was removed by centrifugation using Amicon Ultra 0.5 mL Centrifugal Filters Ultracel 50 K Regenerated Cellulose 50000 NMWL (EMD Millipore, Billerica, MA).

To zirconium-89, an excess of 1 M oxalic acid was added. Slowly Na₂CO₃ was added to bring the pH to 7–7.5. ⁸⁹Zr was added to the DFO-conjugate antibody, and the reaction was mixed at room temperature for 40 min. To chelate free ⁸⁹Zr, 50 mmol · L⁻¹ EDTA, pH 5, was used and removed by centrifugation using sterile saline in Amicon Ultra 0.5 mL Centrifugal Filters Ultracel 50 K Regenerated Cellulose 50000 NMWL (EMD Millipore, Billerica, MA). Instant thin layer chromatography (ITLC) was performed using silica impregnated filter paper (Pall Corporation, Port Washington, NY). The ITLC was run in 50 mmol · L⁻¹ EDTA, pH 5, and subsequently imaged and quantified using the Phosphorimager and the AutoQuant software package, respectively (Packard, PerkinElmer, Hopkinton, MA). For both specific SAC55 and control antibodies, specific activities were in the range of 1.7–2.2 mCi · g⁻¹.