Influence of initial oxygen on the formation of thiol layers

In this study, X-ray photoelectron spectroscopy (XPS) has been used to study thin organic films. For comparison, monolayers were formed on clean and air-exposed metal substrates. Obtained results show that thiols remove contamination oxygen from gold, silver, platinum and copper surfaces. The tightly packed thiolate layers can be formed. In addition, oxygen does not take part in the final bonding of molecules to the surfaces. (c) 2005 Elsevier B.V. All rights reserved

ToF-SIMS study of 1-dodecanethiol adsorption on Au, Ag, Cu and Pt surfaces

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been used to perform a chemical analysis of long-chain thiol (CH3(CH2)(11)SH)-treated gold, silver, copper and platinum surfaces. All the mass peaks from positive and negative ion spectra within the range m/z = 0-2000 u are studied. ToF-SIMS data revealed that on gold, silver and copper substrates 1-dodecanethiol form dense standing-up phases, but on platinum being a catalytically active substrate, we were able to identify also surface-aligned parallel lying molecules in addition to a standing thiolate layer. Our study shows that when ToF-SIMS spectra are analyzed, not only the existence of oligomers but also metal + hydrocarbon fragments give information about the order of SAM. Copyright (c) 2008 John Wiley & Sons, Ltd

The collective excitations and static dipole polarizability in small nanoparticles

Collective dipole excitations for small clusters have been considered in the energy range close to the visible light. The absorption energies and static dipole polarizabilities are estimated. In the case of Ag-8, Na-18, Na-20, Cs-40, Mg-10, Ba-20, Ag-9(+), Na-21(+), and Mg-11(++) clusters, a semiclassical density functional method with the Thomas-Fermi approximation has been used. Also, applications in Al-6, Al-7, (ZnS)(3), and (ZnSe)(4) will be discussed. The results are compared with the available data

Core level spectroscopy of MoS2

X-ray photoelectron spectroscopy has been used to study mineral molybdenite, MoS2. The fitted core level spectra of sulphur 2p and molybdenum 3d states reveal several photon energy sensitive components. The high binding energy component in both spectra is proposed to originate from the uppermost sulphur or molybdenum atoms of an S-Mo-S sandwich layer of the hexagonal structure, respectively. The other features are suggested to be caused by the edge structures formed during the sample cleavage. The edge facets have much stronger chemical properties than the basal planes and they are known as the active sites of MoS2 when it is used as a catalyst. The spectral features and the effect of the structure of UHV cleaved MoS2 on them are discussed. (c) 2006 Elsevier B.V. All rights reserved

Core-level XPS spectra of fullerene, highly oriented pyrolitic graphite, and glassy carbon

The C 1s spectra of fullerene C-60, highly oriented pyrolitic graphite (HOPG) and amorphous carbon (a-C) have been measured using X-ray photoemission. The assumed background due to the inelastic scattering of electrons of these spectra has been subtracted by the Tougaard's method. The relative intensities and the energy positions for the core-level satellites have been determined. For C-60, a comparison of the low energy pi type shake-up satellites gives good agreement between theory and experiment. Also, the energies of these features for fullerene and glassy carbon are very similar, whereas the corresponding energies for HOPG are somewhat larger, presumably, because of the higher density of the latter. Moreover, the atomic force microscopy (AFM) study indicates that the C-60 samples consist of a thick layer of large clusters on the Si(111) surface, which is in line with the molecular character of the XPS spectrum. Furthermore, the broad high energy satellite does not consist of a single plasmon but of many components due to collective excitations characteristic of molecules and solids. These features are discussed in the light of theoretical excitation energies. (C) 2002 Elsevier Science B.V. All rights reserved

Photoelectron spectroscopy study of irradiation damage and metal-sulfur bonds of thiol on silver and copper surfaces

Self-assembled l-dodecanethiol monolayers (SAMs) on silver and copper surfaces have been characterized with X-ray photoelectron spectroscopy (XPS) using both the synchrotron radiation and conventional Mg Kalpha excitation. Irradiation-induced changes in thiolate SAMs on Cu and Ag were observed. The identification of the sulfur species has been done. Results obtained confirm earlier studies of n-alkanethiols on silver. On copper (C12S/Cu), the observed S 2p spectrum is quite broad but the use of different excitation energies enabled us to identify four sulfur species on the surface. A S 2P(3/2) component of copper thiolate is observed at 162.6 eV. Three more doublets (161.9 eV, 163.2 eV and 163.8 eV) have been observed to develop during irradiation and they are assigned to chemisorbed sulfur on copper, to different dialkylsulfides and to sulfur-sulfur bonding, (C) 2004 Elsevier B.V. All rights reserved

Chemisorption of alkyl thiols and S-alkyl thiosulfates on Pt(111) and polycrystalline platinum surfaces

The self-assembled monolayers prepared from 1-dodecanethiol (C12SH) or S-dodecylthio sulfate (Bunte salt, C12SSO3Na) have been characterised on polycrystalline gold and platinum surfaces and on Pt(111). Contact angle and impedance measurements show that the film quality decreases in the order Au/C12SH > Pt/C12SH similar to Au/C12SSO3-Na > Pt/C12S SO3Na. XPS measurements show that the S-SO3 bond of organic thiosulfates is broken on platinum surfaces and the state of the surface-bound sulfur is indistinguishable from that of thiolate. On platinum three sulfur species are formed upon SAM formation and we suggest that the catalytic activity of platinum is responsible for their existence in pristine monolayers. (c) 2005 Elsevier B.V. All rights reserved

Resveratrol, by Modulating RNA Processing Factor Levels, Can Influence the Alternative Splicing of Pre-mRNAs

Alternative pre-mRNA splicing defects can contribute to, or result from, various diseases, including cancer. Aberrant mRNAs, splicing factors and other RNA processing factors have therefore become targets for new therapeutic interventions. Here we report that the natural polyphenol resveratrol can modulate alternative splicing in a target-specific manner. We transfected minigenes of several alternatively spliceable primary mRNAs into HEK293 cells in the presence or absence of 1, 5, 20 and 50 µM resveratrol and measured exon levels by semi-quantitative PCR after separation by agarose gel electrophoresis. We found that 20 µg/ml and 50 µg/ml of resveratrol affected exon inclusion of SRp20 and SMN2 pre-mRNAs, but not CD44v5 or tau pre-mRNAs. By Western blotting and immunofluorescence we showed that this effect may be due to the ability of resveratrol to change the protein level but not the localization of several RNA processing factors. The processing factors that increased significantly were ASF/SF2, hnRNPA1 and HuR, but resveratrol did not change the levels of RBM4, PTBP1 and U2AF35. By means of siRNA-mediated knockdown we depleted cells of SIRT1, regarded as a major target of resveratrol, and showed that the effect on splicing was not dependent on SIRT1. Our results suggest that resveratrol might be an attractive small molecule to treat diseases in which aberrant splicing has been implicated, and justify more extensive research on the effects of resveratrol on the splicing machinery

Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set

We report a measurement of the bottom-strange meson mixing phase \beta_s using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays in which the quark-flavor content of the bottom-strange meson is identified at production. This measurement uses the full data set of proton-antiproton collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity. We report confidence regions in the two-dimensional space of \beta_s and the B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2, -1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in agreement with the standard model expectation. Assuming the standard model value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +- 0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +- 0.009 (syst) ps, which are consistent and competitive with determinations by other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012

Cryo-EM structures of complex I from mouse heart mitochondria in two biochemically defined states.

Complex I (NADH:ubiquinone oxidoreductase) uses the reducing potential of NADH to drive protons across the energy-transducing inner membrane and power oxidative phosphorylation in mammalian mitochondria. Recent cryo-EM analyses have produced near-complete models of all 45 subunits in the bovine, ovine and porcine complexes and have identified two states relevant to complex I in ischemia-reperfusion injury. Here, we describe the 3.3-Å structure of complex I from mouse heart mitochondria, a biomedically relevant model system, in the 'active' state. We reveal a nucleotide bound in subunit NDUFA10, a nucleoside kinase homolog, and define mechanistically critical elements in the mammalian enzyme. By comparisons with a 3.9-Å structure of the 'deactive' state and with known bacterial structures, we identify differences in helical geometry in the membrane domain that occur upon activation or that alter the positions of catalytically important charged residues. Our results demonstrate the capability of cryo-EM analyses to challenge and develop mechanistic models for mammalian complex I