Titer of HRP-301-3 The 0.5 µg/ml of SAH coating standard (Cat # ACT00301 Lot# ACP420210) was coated on micro-titer wells (The top curve). The HRP-301-3 was serially diluted and added to the wells. After incubation of about 60 minutes, substrates were added and OD450 was measured. The flat curve in the bottom showed the experiment control where no SAH was coated to the plate.