FIG. 2.

Impurities in the ATP reagent affected the apparent selectivity of the ADP antibody. (A) Competitive binding assays with ADP (O) and two vendor sources (V1 [▴] and V2 [▪]) of ATP were performed with Ab1 in ADP Detection Mixture 1. The IC₅₀ values were 0.190 mM for ADP, 9 mM for ATP_V1, and 33 mM for ATP_V2. (B) HPLC chromatogram of ADP (—) and two vendor sources (V1 [–.–.] and V2 [– –]) of ATP. Percentage purity of ATP from Vendor 1 and Vendor 2 was calculated to be 95% and 99%, respectively.