Formation Of HeH Research Articles

Identification of a furazolidone metabolite responsible for the inhibition of amino oxidases

1 Furazolidone, a drug widely used in human and veterinary medicine, exhibits inhibition of monoamine oxidase activity, as observed in the tissues of a number of different animal species, including man. The aim of the current study was to determine which of the two possible metabolites, 3-amino-2-oxazolidone (AOZ) or β-hydroxyethylhydrazine (HEH), a well-known carcinogenic compound, is involved in the toxicological effects reported. 2 A new spectrometric method was set up to differentiate intracellular HEH from AOZ inside cells. This method works well at low pH where both AOZ and HEH are free in solution and available to react with the chemical chromophore (DAB). 3 The results confirm that furazolidone has to be metabolized in the intact cell in order to exhibit mitochondrial monoamine oxidase inhibition, whereas AOZ itself is able to exert a reversible monoamine oxidase inhibition. AOZ also inhibits bovine serum amino oxidase. On the contrary, HEH gives irreversible inhibition of both enzymes. However, the reversible nature of the AOZ inhibition with respect to HEH suggests that the two metabolites act by different mechanisms which do not require the biotransformation of AOZ to HEH. 4 Cell lysates, previously incubated with AOZ, were directly analysed and the formation of HEH from AOZ was not detected, supporting the conclusion that the amino oxidase inhibition observed on treatment with furazolidone was attributable to AOZ and not to HEH.

ChemInform Abstract: Quantum‐Mechanical Studies of Radiative Association Reactions: Formation of HeH+, NeH+ and ArH+

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A classical trajectory study of the reaction He(1S) + H2(B1Σu+) → HeH(A2Σ+) + H(2S)

Cross sections for the formation of HeH on the A 1 A′ excited potential surface of HeH2 are calculated in a quasiclassical trajectory study.

A view of bond-formation in HeH+ from the separated species

The detailed course of events that occur during the formation of HeH+ from the separated atoms of He+H+ and He++H is presented and interpreted in terms of the changes in the molecular electron distributions and the forces which they exert on the nuclei. The charge distributions and the forces are calculated from the two-centre Slater elliptic molecular orbital wavefunctions and employing the Hellmann-Feynman theorem. It is seen that the binding in the ground state of the HeH+ molecule is almost covalent while the origin of the binding in the lowest excited state of HeH+ is the long-range attractive force arising from the ion-induced dipole interaction.

Trajectory calculation of the effectiveness of reagent vibration in the H+2+He→HeH++H or He+H+H+ reactions

Total cross sections for the reaction of H+2(v′) with He were calculated for v′=0 to 5 over a range of total energies between 1 and 5 eV using classical mechanics. The potential surface used was an appropriate diatomics-in-molecules function adjusted to fit existing ab initio points. In agreement with experiment, reagent vibrational excitation is very effective in promoting formation of HeH+ or dissociation, a fact which we explain in terms of the increased range of the attractive forces when the H+2 bond is extended. This effect is not properly described by comparison collinear calculations.

Formation of HeH+ from Low-Energy Collisions of Metastable Helium and Molecular Hydrogen

A merging-beams technique has been used to study HeH+ formation resulting from the interaction of a composite beam of He(21S) and He (23S) with a beam of H2. The experiments were conducted over a range of interaction energy W from 0.05 to 10 eV. It was learned that the dominant process for producing HeH+ is the rearrangement ionization reaction He*+H2→HeH++H+e, where He* represents the metastable helium. The experiment consisted of measuring the lab-energy distributions of HeH+. Relative and absolute cross sections were obtained from these distributions. The distributions indicate that, in the center-of-mass system, most of the HeH+ is scattered in the direction of the incident He*. The energies associated with the HeH+ at the peaks of these distributions are very close to those expected for spectator stripping. Conservation of energy for the reaction can only be achieved by assuming that the electron carries away a substantial portion of the available energy. It is shown that the two-step model He*+H2→He+H2+†+e→HeH++H+e (where † indicates ground-state or vibrationally excited H2+) satisfactorily explains the measured lab-energy distributions near W=0.05 eV but does not agree completely with the results for W≥ 2 eV.