Cold atmospheric Plasma Jet-Generated Oxidized Derivatives of Tryptophan and Their Selective Effects on Murine Melanoma and Fibroblast Cells

Cold atmospheric pressure plasma is widely used in research for biomedical applications and is a promising therapy to selectively eradicate cancer cells. However, fundamental information related to the plasma modification of biomolecules in aqueous solution remains elusive. In this work, we studied the chemical basis of tryptophan (Trp) oxidation using an Ar plasma jet and investigated the effects of plasma-treated tryptophan (PTT) on cell viability. The results show that the main product of the Trp of plasma induced oxidation is a mixture of hydroxyl derivatives and hydroperoxides in aqueous form. The products result primarily from the hydroxyl radical (·OH) attacking the Trp, which can be explained by the interaction with both the aromatic and the pyrrole rings. We observed that the PTT has a different proliferation effect between the growth of the B16 melanoma cells and the L929 fibroblast cells. The experimental results indicated that the effect of the PTT is dose-dependent in the B16 cells, ranging from cell proliferation to cytotoxic damage with apoptosis. Furthermore, we examined the intracellular changes in hydrogen peroxide (H₂O₂) and superoxide radicals (\({\text{O}}_{2}^{{\bar{ \cdot }}}\)) following the Trp-derived treatment using the fluorescence probe method. Rigorous identification of the reactive oxygen species (ROS) produced by PTT in cells as \({\text{O}}_{2}^{{\bar{ \cdot }}}\) and H₂O₂ helped establish the cellular source of ROS. It is shown that the intracellular H₂O₂ might originate from the activation of NADPH. These results suggested that the amino acid and protein hydroperoxides may play a crucial role in the action of plasma on the biologic target.     

The tautomerization of H2NCH2C(OH)NH to H2NCH2CONH2 in the interstellar medium

The tautomerization of H2NCH2C(OH)NH to H2NCH2CONH2 is an important step by way of Strecker synthesis for the production of glycine in the interstellar medium (ISM) with respect to the origin of amino acids on the early Earth.Our work indicates two mechanisms for the tautomerization to occur.k CVT/SCT (rate constant) is 45.6s-1 at 50 K,obtained with the small curvature tunneling (SCT) approximation and canonical variational transition state theory (CVT),to support one mechanism assisted by quantum tunneling...