Selective inhibitor of protein kinase G (Ki values are 0.23, 4 and > 10 μM for inhibition of PKG, PKC and PKA respectively). Inhibits SNP-stimulated PKG activity with an IC50 of 60 nM in dispersed smooth muscle cells and has little effect on PKA activity at concentrations of up to 10 μM. Purity 98%. MW (observed): 495.53