Search results for "substrate"
showing 10 items of 1018 documents
Reflection high energy electron diffraction as a tool in cluster deposition experiments
2010
Reflection high energy electron diffraction (RHEED) is used to study the structure and orientation of mass-filtered iron clusters upon deposition ontoW(110). The present setup enables in situ investigations during deposition and thermal annealing. Particles as small as 2 nm at low density on the surface can be studied. The experiments reveal that larger particles with a diameter of about 13 nm are randomly oriented on the substrate with a preferred tendency to rest on their surface facets. Thermal annealing leads to a partial realignment and a significant flattening of the particles. In contrast 2 nm particles are found to align spontaneously in an epitaxial manner on W(110). Thermodynamic …
Monolayer Structure of Arachidic Acid on Graphite
2010
The self-assembly of arachidic acid (C(19)H(39)COOH) at the liquid solid interface between 1-phenyloctane (C(6)H(5)(CH(2))(7)CH(3)) and highly oriented pyrolytic graphite (HOPG) is studied by scanning tunneling microscopy (STM) to identify the structure of the monomolecular film. We observe the formation of highly ordered domains with molecules oriented in three different orientations compatible with the symmetry of the HOPG substrate, a spontaneous enantiomeric separation of the pro-chiral molecules, and reveal structural details with submolecular resolution. To determine the surface unit cell with an intrinsic calibration to the substrate atomic structure, the intermolecular distance is p…
Electronic and vibrational properties of meso-tetraphenylporphyrin on silver substrates.
2014
The electronic and vibrational properties of meso-tetraphenylporphyrin (mtpp) on silver substrates are investigated using UV–vis and surface-enhanced resonance Raman scattering (SERRS) spectroscopy. Whereas the vibrational signatures associated with the tetrapyrrole backbone exhibit minor variations throughout sequences of consecutively recorded SERRS spectra, the C═C stretching vibrational modes localized on the meso-phenyl moieties of mtpp exhibit noticeable intensity fluctuations, masked in the average SERRS response. We attribute the observed vibrational-state-specific blinking events to conformational changes in mtpp, namely, torsional flexibility which mediates the coupling between th…
Retinal neurodegenerative changes in the adult insulin receptor substrate-2 deficient mouse.
2014
Abstract Insulin receptor substrate-2 (Irs2) mediates peripheral insulin action and is essential for retinal health. Previous investigations have reported severe photoreceptor degeneration and abnormal visual function in Irs2-deficient mice. However, molecular changes in the Irs2 − / − mouse retina have not been described. In this study, we examined retinal degenerative changes in neuronal and glial cells of adult (9- and 12-week old) Irs2 − / − mice by immunohistochemistry. 9-week old Irs2 − / − mice showed significant thinning of outer retinal layers, concomitant to Muller and microglial cell activation. Photoreceptor cells displayed different signs of degeneration, such as outer/inner…
Flash-Floods Influence Macroinvertebrate Communities Distribution in Lotic Ecosystems
2019
Abstract Stream dwelling invertebrate populations are facing an ample array of stressors including the habitat imbalance caused by important floods. In this research we used a novel way to estimate the impact of floods upon the substrate, by utilising a remote variable named “flash-flood potential” (FFP), which accounts for the site slope and the average slope of the upstream catchment. The results showed that certain groups are sensitive to the influence of the FFP whereas other are not. We propose this remote variable as a surrogate for assessing stress imposed by floods and sediment scouring for lotic macroinvertebrates.
Selective Inhibition of STAT3 with Respect to STAT1: Insights from Molecular Dynamics and Ensemble Docking Simulations
2016
STAT3 protein, which is known to be involved in cancer development, is a promising target for anticancer therapy. Successful inhibitors of STAT3 should not affect an activity of closely related protein STAT1, which makes their development challenging. The mechanisms of selectivity of several existing STAT3 inhibitors are not clear. In this work, we studied molecular mechanisms of selectivity of 13 experimentally tested STAT3 inhibitors by means of extensive molecular dynamics and ensemble docking simulations. It is shown that all studied inhibitors bind to the large part of the protein surface in an unspecific statistical manner. The binding to the dimerization interface of the SH2 domain, …
Surface preparation by using laser cleaning in thermal spray
2008
International audience; Pulsed laser cleaning has emerged as a promising technology to challenge traditional surface preparation methods. This paper introduces the PROTAL(R) process, which combines an in situ pulsed laser cleaning with thermal spraying techniques. This laser surface preparation avoids some drawbacks of the traditional degreasing and sand-blasting stages prior to thermal spraying, which is especially meaningful for ductile and notch-sensitive materials. The laser induced phenomenon and the significant role of such laser irradiation in the coating deposition are presented. (C) 2008 Laser Institute of America.
Yeast contains multiple forms of histone acetyltransferase.
1989
We have assayed several methods to quantitatively recover yeast histone acetyltransferases in an attempt to study the multiplicity of enzymatic activities. Two methods, namely (NH4)2SO4 precipitation and salt dissociation of chromatin in 0.5 M NaCl, yielded convenient preparations of total histone acetyltransferases. DEAE-Sepharose chromatography of the crude extracts resulted in the separation of three peaks of activity when total yeast histones were used as substrate. However, the scanning of the enzymatic activity toward individual histones along the chromatography, achieved by determining the specific activity of the individual histones after incubating whole histones and [14C]acetyl-Co…
Site specificity of pea histone acetyltransferase B in vitro.
1993
Histone acetyltransferase B from pea embryonic axes has been purified approximately 300-fold by a combination of chromatographic procedures, including affinity chromatography on histone-agarose. The enzyme preparation has been used for the in vitro transfer of acetyl groups from [1-14C]acetyl-CoA to non-acetylated pea histone H4. Up to three acetyl groups can be introduced into the histone. The resulting mono-, di-, and triacetylated H4 isoforms were separated and sequenced to determine the acetylated sites. Only sites 5, 12, and 16 were used by histone acetyltransferase B, but no clear preference among them was observed. The absence of modification of other potentially acetylatable sites i…
HAT1 and HAT2 Proteins Are Components of a Yeast Nuclear Histone Acetyltransferase Enzyme Specific for Free Histone H4
1998
We have analyzed the histone acetyltransferase enzymes obtained from a series of yeast hat1, hat2, and gcn5 single mutants and hat1,hat2 and hat1,gcn5 double mutants. Extracts prepared from both hat1 and hat2 mutant strains specifically lack the following two histone acetyltransferase activities: the well known cytoplasmic type B enzyme and a free histone H4-specific histone acetyltransferase located in the nucleus. The catalytic subunits of both cytoplasmic and nuclear enzymes have identical molecular masses (42 kDa), the same as that of HAT1. However, the cytoplasmic complex has a molecular mass (150 kDa) greater than that of the nuclear complex (110 kDa). The possible functions of HAT1 a…