The stability of binuclear dinitrosyl iron complexes with various thiol-containing ligands (glutathione, N-acetyl-L-cysteine, mercaptoethanol, mercaptosuccinate, and L-cysteine) upon exposure to air at room temperature and neutral pH, determined by the efficiency of oxidation of thiol-containing ligands by oxygen, was comparatively assessed. The complexes with glutathione and N-acetyl-L-cysteine proved to be the most stable, while the complexes with L-cysteine were the least stable. Similar relationships were obtained when assessing the stability of the same complexes upon storage in aqueous solutions at pH 1–2, determined under these conditions by the efficiency of protonation of the thiol group of the thiol-containing ligands. The obtained results provide a basis for using complexes with L-cysteine, due to their low stability, as the most effective donors of NO molecules and nitrosonium cations NO+ in experiments on the effect of binuclear dinitrosyl iron complexes on living organisms.
Raevskaya et al. (Thu,) studied this question.