Figure 5: Response of the probes with increasing concentrations of Na₂S.

(a–d) Imaging of aqueous sulphide in HeLa cells after 15 min incubation using SFP-1 (12) or SFP-2 (20). For 12, excitation and data collection were performed using the corresponding filters for DAPI (blue) on a DSU spinning disk confocal. For 20, similar experiments were performed using the filter for green fluorescent protein (green). Images were obtained by using widefield fluorescence capture with SFP-1 (10 μM), with increasing concentrations of Na₂S: (a) 0 μM, (b) 10 μM, (c) 50 μM, and (d) 100 μM. With SFP-2 (2 μM), confocal fluorescence capture was utilized, and Na₂S concentrations were varied from (e) 0 μM, (f) 50 μM, (g) 100 μM, and (h) 200 μM. Scale bar represents 20 μm.