Monobromobimane fluoropure grade

Antimycin A, equine heart ferric Cyt C, HSA, iodoacetamide, and Na₂S nonahydrate (99.99%) were purchased from Sigma-Aldrich. Sodium disulfide (Na₂S₂) was from Dojindo Molecular Technologies, and monobromobimane FluoroPure grade was from Molecular Probes (Grand Island, NY). GYY4137, AP39, and MeRho-Az were synthesized in house as described previously.^{35 (link),36 ,49} 2-(Methylsulfonyl)-1,3-benzothiazole was from Santa Cruz Biotechnology, and CN-Cy3 was synthesized as reported previously.^{33 (link)} Murine procaspase 9 was from Enzo Life Science. The siRNA for Cyt C was purchased from Santa Cruz Biotechnology. For the anaerobic experiments, buffers were purged with argon. To maintain high purity, Na₂S solutions were made in an argon box by dissolving solid Na₂S·9H₂O into argon-purged water, as recommended.^{2 (link),19 (link)}

Equine skeletal muscle Fe^III-Mb, Na₂S nonahydrate,
and L-cystine, H₂S solution (0.8 M) in tetrahydrofuran and xylenol
orange were from Sigma (St. Louis, MO). Monobromobimane (FluoroPure grade) was
from Molecular Probes (Grand Island, NY) and HEPES was from Fisher Scientific
(Walham, MA). Recombinant human γ-cystathionase (CSE)
was prepared as described previously.^{27 (link)}