Chicago Sky Blue 6B

COC1=C (C=CC (=C1) C2=CC (=C (C=C2) N=NC3=C (C4=C (C=C3) C (=CC (=C4N) S (=O) (=O) [O-]) S (=O) (=O) [O-]) O) OC) N=NC5=C (C6=C (C=C5) C (=CC (=C6N) S (=O) (=O) [O-]) S (=O) (=O) [O-]) O.[Na+].[Na+].[Na+].[Na+]

Chicago Sky Blue 6B (Direct Blue 1, Pontamine sky blue) is a counterstain for background autofluorescence in fluorescence and immunofluorescence histochemistry. It is an inhibitor of macrophage migration inhibitory factor (MIF) with an IC50 of 0.81 μM.