Fig. 4.

Mean fluorescence response of SSP4 (5 μM) in the presence of: (1) 25 μM cysteine polysulfide (Cys-polysulfide); (2) 25 μM sodium disulfide (Na₂S₂); (3) 25 μM elemental sulfur (S₈); (4) 1 mM l-cysteine (Cys); (5) 1 mM glutathione (GSH); (6) 1 mM homocysteine (Hcy); (7) 30 μΜ methionine (Met); (8) 100 μM N-acetyl-l-cysteine (NAC); (9) 100 μM oxidized glutathione (GSSG); (10) 100 μM sodium sulfate (Na₂SO₄); (11) 100 μM sodium thiosulfate (Na₂S₂O₃); (12) 100 μM sodium sulfite (Na₂SO₃); (13) 100 μM sodium sulfide (Na₂S); (14) 150 μM glycine (Gly); (15) 55 μM tyrosine (Tyr); (16) 40 μM tryptophan (Trp); (17) 100 μM arginine (Arg); (18) probe only. Results are expressed as mean ± SEM (n = 3).