Decomposition of protonated ronidazole studied by low-energy and high-energy collision-induced dissociation and density functional theory.

Nitroimidazoles are important compounds in medicine, biology, and the food industry. The growing need for their structural assignment, as well as the need for the development of the detection and screening methods, provides the motivation to understand their fundamental properties and reactivity. Here, we investigated the decomposition of protonated ronidazole [Roni+H] in low-energy and high-energy collision-induced dissociation (CID) experiments.

Interactions of low-energy electrons with the FEBID precursor chromium hexacarbonyl (Cr(CO)).

Interactions of low-energy electrons with the FEBID precursor Cr(CO) have been investigated in a crossed electron-molecular beam setup coupled with a double focusing mass spectrometer with reverse geometry. Dissociative electron attachment leads to the formation of a series of anions by the loss of CO ligand units. The bare chromium anion is formed by electron capture at an electron energy of about 9 eV.

High-energy collision-induced dissociation of histidine ions [His + H] and [His - H] and histidine dimer [His + H].

Rationale: Histidine (His) is an essential amino acid, whose side group consists of an aromatic imidazole moiety that can bind a proton or metal cation and act as a donor in intermolecular interactions in many biological processes. While the dissociation of His monomer ions is well known, information on the kinetic energy released in the dissociation is missing.

Methods: Using a new home-built electrospray ionization (ESI) source adapted to a double-focusing mass spectrometer of BE geometry, we investigated the fragmentation reactions of protonated and deprotonated His, [His + H] and [His - H] , and the protonated His dimer [His  + H] , accelerated to 6 keV in a high-energy collision with helium gas.