Cysteine-Activated Small-Molecule H2Se Donors Inspired by Synthetic H2S Donors

The importance of selenium (Se) in biology and health has become increasingly clear. Hydrogen selenide (H2Se), the biologically available and active form of Se, is suggested to be an emerging nitric oxide (NO)-like signaling molecule. Nevertheless, the research on H2Se chemical biology has technique difficulties due to the lack of well-characterized and controllable H2Se donors under physiological conditions, as well as a robust assay for direct H2Se quantification. Motivated by these needs, here, we demonstrate that selenocyclopropenones and selenoamides are tunable donor motifs that release H2Se upon reaction with cysteine (Cys) at pH 7.4 and that structural modifications enable the rate of Cys-mediated H2Se release to be tuned. We monitored the reaction pathways for the H2Se release and confirmed H2Se generation qualitatively using different methods. We further developed a quantitative assay for direct H2Se trapping and quantitation in an aqueous solution, which should also be operative for investigating future H2Se donor motifs. In addition, we demonstrate that arylselenoamide has the capability of Cys-mediated H2Se release in cellular environments. Importantly, mechanistic investigations and density functional theory (DFT) calculations illustrate the plausible pathways of Cys-activated H2Se release from arylselenoamides in detail, which may help understand the mechanistic issues of the H2S release from pharmacologically important arylthioamides. We anticipate that the well-defined chemistries of Cys-activated H2Se donor motifs will be useful for studying Se biology and for development of new H2Se donors and bioconjugate techniques.