Structures of Gas-Phase Hydrated Phosphotyrosine Revealed by Soft X-ray Action Spectroscopy.

Gas-phase near-edge X-ray absorption mass spectrometry (NEXAMS) was employed at the carbon and oxygen K-edges to probe the influence of a single water molecule on the protonated phosphotyrosine molecule. The results of the photodissociation experiments revealed that the water molecule forms two bonds, with the phosphate group and another chemical group. By comparing the NEXAMS spectra at the carbon and oxygen K-edges with density functional theory calculations, we attributed the electronic transitions responsible for the observed resonances, especially the transitions due to the presence of the water molecule.

A velocity map imaging spectrometer for measuring absolute differential cross sections for ion-induced electron emission from molecules.

In this paper, we present a newly developed crossed beam experimental setup that utilizes the velocity map imaging (VMI) technique to simultaneously measure both the kinetic energy and emission angle of electrons emitted from atoms or molecules upon ion collision. The projectile ion beam with keV to MeV kinetic energy orthogonally crosses the neutral target beam produced by an effusion cell. The emitted electrons are extracted and analyzed by a multi-electrode VMI spectrometer.

An electrostatic in-line charge-state purification system for multicharged ions in the kiloelectronvolt energy range.

The performance of a newly built omega type electrostatic analyzer designed to act as an in-line charge-state purification system for ions in the kiloelectronvolt energy range is reported. The analyzer consists of a set of four consecutive electrostatic 140° concentric cylindrical electrodes enclosed by Matsuda electrodes. This setup was recently tested and validated using O, Ar, and Xe ion beams at an energy of 14 qkeV at the ARIBE facility.

A tandem mass spectrometer for crossed-beam irradiation of mass-selected molecular systems by keV atomic ions.

In the present paper, we describe a new home-built crossed-beam apparatus devoted to ion-induced ionization and fragmentation of isolated biologically relevant molecular systems. The biomolecular ions are produced by an electrospray ionization source, mass-over-charge selected, accumulated in a 3D ion trap, and then guided to the extraction region of an orthogonal time-of-flight mass spectrometer. Here, the target molecular ions interact with a keV atomic ion beam produced by an electron cyclotron resonance ion source.

Formation and Fragmentation of Protonated Molecules after Ionization of Amino Acid and Lactic Acid Clusters by Collision with Ions in the Gas Phase.

Collisions between O(3+) ions and neutral clusters of amino acids (alanine, valine and glycine) as well as lactic acid are performed in the gas phase, in order to investigate the effect of ionizing radiation on these biologically relevant molecular systems. All monomers and dimers are found to be predominantly protonated, and ab initio quantum-chemical calculations on model systems indicate that for amino acids, this is due to proton transfer within the clusters after ionization. For lactic acid, which has a lower proton affinity than amino acids, a significant non-negligible amount of the radical cation monomer is observed.