Kinetic fingerprint betrays active contaminant of nonpurified pyridine dinucleotides. (A–C) Macroscopic T5L-TRPM2 current repeatedly activated by brief exposures to 32 µM ADPR (dark blue bars) or saturating concentrations of nonpurified NAD (1 mM; A, green bars), NAAD (1 mM; B, blue bars), or NAADP (2 mM; C, purple bars) in the continued presence of saturating Ca²⁺ (black bars). Current decay time courses upon nucleotide removal were fitted by single-exponential functions (colored curves), with time constants indicated (in seconds). (D) Average T5L-TRPM2 current relaxation time constants (in seconds) upon sudden removal of saturating NAD (green), NAAD (blue), or NAADP (purple) in the maintained presence of Ca²⁺. Analogous parameters for ADPR (dark blue) and ADPRP (red) are replotted from Fig. 5 D for comparison. Error bars represent mean ± SEM.