Fig. 3

Schematic of HPLC based screening assay for PDE5A1-inhibitors. A Linear correlation of the standard curve for cGMP quantitatively detected by HPLC. The peaks from the bottom to the top showed the samples was prepared by 0.18 nM, 0.73 nM, 2.93 nM, 11.72 nM, 46.88 nM, 187.50 nM, 750.00 nM sildenafil. (B) The standard curve of cGMP. C Titration of PDE5A1 in the presence of 50 µg/mL of cGMP detected by HPLC. D Titration of cGMP in the presence of 0.15 µg/mL PDE5A1 (lower line) and the cGMP standard curve without PDE5A1 (upper line). E DMSO tolerance study for 0.15 µg/mL PDE5A1 in the presence of 7.5 µg/mL cGMP for 90 min reaction at 35 ℃