Laser Desorption Supersonic Jet Spectroscopy of Octopamine by Its Hydrochloride Salt

Abstract

Octopamine is a phenol analog of noradrenaline and acts as a neurotransmitter in invertebrates such as octopus. It is available as a hydrochloride salt to avoid air oxidation. We applied laser desorption supersonic jet technique to octopamine hydrochloride without any chemical preparations and found that molecular ion of octopamine, not salt, is observed. Resonance-enhanced 2-photon ionization and ultraviolet–ultraviolet hole-burning spectra of octopamine were measured, and four conformers were identified. This number of conformations is rationalized by conformations of ethanolamine chain and orientations of phenolic OH.

Laser Desorption of Tryptophan from Tryptophan–HCl Salt on a Graphite Substrate

“…Chemical processing is required to recover a neutral amine compound from its salt, thus limiting the applicability of laser‐desorption spectroscopy of biomolecules. However, recently Fujii and coworkers have shown that neutral octopamine can be desorbed from its HCl salt . Our group has also succeeded in desorbing intact biomolecules from its HCl salt.…”

“…However, recently Fujii and coworkers have shown that neutral octopamine can be desorbed from its HCl salt. 13 Our group has also succeeded in desorbing intact biomolecules from its HCl salt. We obtained REMPI spectra of laser-desorbed Trp and Trp-HCl salt, and confirmed that both of the spectra match well with the previously reported REMPI spectrum of Trp.…”