Biomedical subjects

Judit Sztáray

Publications and source records attributed to Judit Sztáray.

3 recordsLinked to original sources

PubMed2005

Internal energy distribution in electrospray ionization.

Internal energies and energy distributions were studied using the 'survival yield' method developed previously. In addition to conventional benzylpyridinium salts, protonated esters (fragmenting by rearrangement) and protonated leucine enkephalin were also used, extending the validity of the technique. Fragmentation processes were studied in the cone voltage region and modeled by the RRKM-based MassKinetics program. The results show that the shapes of the energy distributions are similar to thermal distributions. The mean internal energies are very similar for all compound classes studied, and show a linear increase with collision energy in the 10-50 eV region.

Energy Transfer↗

PubMed2004

Electron impact ionization in helium nanodroplets: controlling fragmentation by active cooling of molecular ions.

Reported here is a study of the effects of liquid helium cooling on the fragmentation of ions formed by electron impact mass ionization. The molecules of interest are picked up by the helium nanodroplets as they pass through a low pressure oven. Electron impact ionization of a helium atom in the droplet is followed by resonant charge transfer to neighboring helium atoms. When the charge is transferred to the target molecule, the difference in the ionization potentials between helium and the molecule results in the formation of a vibrationally hot ion. In isolation, the hot parent ion would undergo subsequent fragmentation. On the other hand, if the cooling due to the helium is fast enough, the parent ion will be actively cooled before fragmentation occurs. The target molecule used in the present study is triphenylmethanol (TPM), an important species in synthetic chemistry, used to sterically protect hydroxyl groups. Threshold PhotoElectron PhotoIon COincidence (TPEPICO) experiments are also reported for gas-phase TPM to help quantify the ion energetics resulting from the cooling effects of the helium droplets.

Journal Article↗

PubMed2004

Kinetic energy release of protonated methanol clusters using the low-temperature fast-atom bombardment: experiment and theory combined.

Low-temperature fast-atom bombardment was found to be an excellent method for generating large protonated methanol clusters, (CH(3)OH)(n)H(+) (n = 2 to 15). Metastable dissociations of these clusters, involving elimination of one methanol molecule, were studied using mass-analyzed ion kinetic energy spectra (MIKES). From metastable peak profiles kinetic energy release (KER) distributions were obtained, even for clusters as large as (CH(3)OH)(15)H(+). The results were analyzed by a simple thermal model, by the finite heat bath theory (FHBT) and by the RRKM-based MassKinetics algorithm. The KER distribution was shown to correspond to a three-dimensional translational energy distribution, implying statistical energy partitioning in the transition state. The mean KER values and transition state temperatures were found to increase with cluster size, reaching 25 meV and approximately 210 K for large clusters (n = 10).

Journal Article↗