Fig. 1. Comparison of total dissolved sulfide concentration following 2 h exposure to 0–3.2% H₂S in cell-free incubation buffer alone (A–F, blue symbols, N=15, with the same data set shown in each plot) or in cell-free incubation buffer with added hypotaurine (HT) or antioxidants (A–F, red symbols). (A) 50 mmol l^–1 HT (hypotaurine), (N=3–9). (B) 3 mmol l^–1 GEE (glutathione ethyl ester) (N=6). (C) 1.0 mmol l^–1 NAC (N-acetylcysteine) (N=6). (D) 0.10 mmol l^–1 ASC (L-ascorbic acid) (N=6). (E) 3.0 mmol l^–1 Tempol (4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl) (N=6). (F) 0.10 mmol l^–1 Trolox (6-hydoxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) (N=6). Data are means ± s.e.m. (G) Comparison of total dissolved sulfide concentration following 2 h exposure to 0–3.2% H₂S in cell-free incubation buffer alone (0 HT) and with 0.50, 5.0 and 50 mmol l^–1 HT. For each H₂S percentage, the sulfide concentration is expressed relative to the concentration in the absence of HT. Data are means ± 1 standard deviation. For all plots, asterisks represent significant differences from the dissolved sulfide concentration in incubation buffer alone at the same H₂S percentage.