Ricin Toxin Purification and Characterization

Ricin toxin (Ricinus communis agglutinin II) was purchased from Vector Laboratories (Burlingame, CA) and was dialyzed to remove sodium azide, as described [29 (link)]. Native RTA from Ricinus communis seeds was obtained from BEI Resources (Catalog NR-2619; Manassas, VA) [30 (link)]. HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) buffer consisted of 0.22 g/L KCl, 7.7 g/L NaCl, 0.14 g/L Na₂HPO₄, 1.8 g/L D-glucose, 7.15 g/L HEPES, and 0.001 g/L phenol red in distilled water. Gey’s balanced salt solution (GBSS) contained 0.220 g CaCl₂.2H₂O, 0.370 g/L KCl, 0.030 g/L KH₂PO₄, 0.210 g/L MgCl₂.6H₂O, 0.070 g/L MgSO₄.7H₂O, 8.00 g/L NaCl, 0.227 g/L NaHCO₃, 0.120 g/L Na₂HPO₄, and 1.00 g/L D-glucose in distilled water. Magnetic-activated cell sorting (MACS) buffer consisted of 0.5% w/v bovine serum albumin (BSA) and 2 mM ethylenediaminetetraacetic acid (EDTA) in phosphate buffer saline (PBS) without Ca²⁺ and Mg⁺ (Thermo Fisher, Waltham, MA, USA). Staining/wash buffer (SWB) for flow cytometry contained 2% (w/w) fetal bovine serum (FBS; ThermoFisher) in PBS.