2.1 Materials

The wt-like-G3C9-derived PON1 variants 2D8, IIG1, VIID2 and PG11 were expressed and purified as described by Goldsmith et al. [9]. Variant 11C1 was generated by M. Goldsmith et al, (this issue). The evolution of rePON1 4E9 was reported by Gupta et al. [8], and PTE-C23 was described by Cherny et al. [11]. Human acetylcholinesterase (rhAChE) was expressed and purified in the Israeli Center for Structural Proteomics (ISPC), at the Weizmann Institute of Science. Cyclosarin (GF) was obtained in situ, in water, at non-hazardous concentrations, as described earlier [8].