Single Silver Ions Facilitate Intramolecular Hydrogen Atom Transfer and C−C Bond Dissociation of Neurotransmitters^†

Tryptophan (Trp), tyrosine (Tyr), and histidine (His), known as three essential amino acids, are also precursors of vital neurotransmitters in brain nutrient metabolism. In this study, we have conducted a gas-phase study on their interactions with silver ions by a customized reflectron time-of-flight mass spectrometer combined with a magnetron sputtering source and a downstream flow tube reactor. It is unveiled that these physiological molecules are readily dissociated in the presence of Ag⁺ ions, giving rise to fragmentation and recombination products. Utilizing density functional theory calculations, we have clarified the reaction mechanism of the dissociative process. It is found that the silver ions facilitate the hydrogen atom transfer reaction followed by competitive C_α−C_β and C_β−C_γ bond dissociation. This study enriches the basic and precise properties of such neurotransmitter molecules and helps us understand similar physiological mechanisms in vivo.