Probing the selectivity of Li and Na cations on noradrenaline at the molecular level.

Although several mechanisms concerning the biological function of lithium salts, drugs having tranquilizing abilities, have been proposed so far, the key mechanism for its selectivity and subsequent interaction with neurotransmitters has not been established yet. We report ultraviolet (UV) and infrared (IR) spectra under ultra-cold conditions of Li+ and Na+ complexes of noradrenaline (NAd, norepinephrine), a neurotransmitter responsible for the body's response to stress or danger, in an effort to provide a molecular level understanding of the conformational changes of NAd due to its interactions with these two cations. A detailed analysis of the IR spectra, aided by quantum chemical calculations, reveals that the Li+-noradrenaline (NAd-Li+) complex forms only an extended structure, while the NAd-Na+ and protonated (NAd-H+) complexes form both folded and extended structures.

A conformational study of protonated noradrenaline by UV-UV and IR dip double resonance laser spectroscopy combined with an electrospray and a cold ion trap method.

The conformer-selected ultraviolet (UV) and infrared (IR) spectra of protonated noradrenaline were measured using an electrospray/cryogenic ion trap technique combined with photo-dissociation spectroscopy. By comparing the UV photo dissociation (UVPD) spectra with the UV-UV hole burning (HB) spectra, it was found that five conformers coexist under ultra-cold conditions. Based on the spectral features of the IR dip spectra of each conformer, two different conformations on the amine side chain were identified.

Gas phase ultraviolet and infrared spectroscopy on a partial peptide of β2-adrenoceptor SIVSF-NH2 by a laser desorption supersonic jet technique.

Laser desorption supersonic jet laser spectroscopy has been applied to a penta-peptide, Ser-Ile-Val-Ser-Phe-NH2 (SIVSF-NH2), which is a partial sequence of a binding site in a β2-adrenaline receptor protein. By comparing the resonance enhanced multiphoton ionization spectrum with the ultraviolet-ultraviolet hole burning (HB) spectrum, it is concluded that only a single conformer exists. The infrared (IR) spectrum of the X-H stretching region, measured by IR dip spectroscopy, shows that all of the OH and NH groups form hydrogen bonds.