Cell-permeable. A slow, tight binding and highly selective inhibitor of iNOS (inducible nitric oxide synthase/NOS II) (Kd ≤ 7 nM). In contrast, inhibition of nNOS and eNOS is weaker and rapidly reversible with K? values of 2 and 50 μM respectively. Inhibits tumor growth in vivo. Prevents circulatory failure but not organ injury induced by endotoxin. Displays protective effects in oxygen-deprived brain slices. MW: 250.17. Purity ≥98% by NMR