Hindered rotational physisorption states of H2 on Ag(111) surfaces.

We have investigated the physisorption states of H2 on Ag(111) surfaces. To clarify the accurate adsorption properties of H2 on Ag(111), we performed first-principles calculations based on spin-polarized density functional theory (DFT) with the semiempirical DFT-D2 method and the newly-developed exchange functional with the non-local correlation functional vdW-DF2 (rev-vdW-DF2). We constructed exhaustive potential energy surfaces, and revealed that non-negligible out-of-plane potential anisotropy with a perpendicular orientation preference exists even for H2 physisorption on planar Ag(111), as predicted by previous results of resonance-enhanced multiphoton ionization spectroscopy and temperature-programmed desorption experiments. Therefore, the molecular rotational ground states of ortho-H2 split into two energy levels in the anisotropic potential. The obtained adsorption energy and the number of bound states, including the zero-point energies and the rotational energy shift, agree with diffractive and rotationally mediated selective adsorption scattering resonance measurements. The origin of the potential anisotropy on Ag(111) is a combination of the London dispersion interaction and the virtual transition of the metal electron to the unoccupied molecular state.

Surface magnetism in O2 dissociation-from basics to application.

First-principles calculations were performed to investigate magnetic phenomena in surface reactions involving O(2). We present two magnetized surface cases: (1) oxidation of paramagnetic Ag, and magnetic properties of the high coverage oxide phase, which correspond to a magnetic impurity superlattice on paramagnetic surfaces and (2) oxidation of ferromagnetic Pt, represented by the Pt layer on M (M = Fe and Co) relevant to the oxidation reduction reaction (ORR) on Pt, in relation to both fundamental and application interests. In the first case, we found that the dissociative adsorption of O(2), resulting in oxide phases in Ag(111), reveals interesting magnetic interactions. We note that the magnetic states are induced by the ferromagnetic superexchange interactions and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions. Specifically, the superlattice structures with short O-O distances have an effective ferromagnetic superexchange and RKKY interaction. In the second case, we found that a magnetic moment is induced on the Pt layer by the M substrate. The spin polarization of Pt-d states is due to hybridization with M-d states. The d-band center (ε(d)) of Pt (on M), is shifted downwards with respect to pure Pt. However, because of the spin polarization, the otherwise filled spin-down d(zz) orbital in paramagnetic pure Pt is shifted towards the Fermi level. This promotes π(z↑)-d(zz↓) interactions, which influences the O(2)-Pt interaction at O(2) far from the surface. Details and mechanisms of these two magnetic phenomena are discussed.

Generation of chromioenamines by reduction of O-acetyloximes with chromium(II) and their application.

Chromioenamines can be generated by treatment of O-acetyloximes with chromium(II) via two steps of one-electron reduction and successive isomerization, and the species react with aldehydes to give gamma-amino alcohols after reduction with LiAlH4.

An acute exercise-induced translocation of beta-adrenergic receptors in rat myocardium.

The effect of acute exercise (treadmill running) on rat myocardium beta-adrenergic receptors (beta-AR) was studied. beta-AR was identified in purified sarcolemmal membrane fractions and light vesicle fractions. In control hearts, the number of beta-AR was 21.25 +/- 2.25 and 20.89 +/- 2.89 fmol/mg protein (mean +/- SE) in sarcolemmal membranes and light vesicles, respectively. Immediately after a single bout of dynamic exercise, about 35% of beta-AR was transferred from light vesicles to sarcolemmal membranes (p less than 0.05); concomitantly, isoproterenol-stimulated adenylate cyclase activity also significantly increased in sarcolemmal membranes (p less than 0.05). These results suggest that acute exercise provokes the translocation of beta-AR from a presumably intracellular site (light vesicles) to functional membrane fractions (sarcolemmal membranes) in rat myocardium.

Some characteristics of the beta-adrenergic system in rat adipocyte membranes after the chronic administrations of isoproterenol.

The effects of chronic administrations of isoproterenol (IPR) on adipocyte beta-adrenergic system were investigated. A 21-days in vivo administration of IPR (2.5 mg/kg BW/day) reduced (-)-IPR- and 5'-guanylylimidodiphosphate-stimulated adenylate cyclase activities. Moreover, the number of beta-adrenergic receptors (beta-AR) and (-)-IPR-stimulated [3H]GDP release from adipocyte membranes were significantly depressed in the treated rats compared to controls. These results suggest that the desensitized response of adenylate cyclase to beta-agonists, induced by chronic in vivo administrations of IPR, may result from impaired coupling efficiency between beta-AR and adenylate cyclase with the significant loss of the number of beta-AR and possible change(s) of guanine nucleotide regulatory proteins.