Characterization, substrate elemental

The chemical and electronic properties of elements at the interfaces between very thin films and bulk substrates are important in several technological areas, particularly microelectronics, sensors, catalysis, metal protection, and solar cells. To study conditions at an interface, depth profiling by ion bombardment is inadvisable, because both composition and chemical state can be altered by interaction with energetic positive ions. The normal procedure is, therefore, to start with a clean or other well-characterized substrate and deposit the thin film on to it slowly at a chosen temperature while XPS is used to monitor the composition and chemical state by recording selected characteristic spectra. The procedure continues until no further spectral changes occur, as a function of film thickness, of time elapsed since deposition, or of changes in substrate temperature. 

Dimercury(I) n complexes are formed between aromatic compounds and Hg2(AsF6)2 in liquid S02 as solvent.113,121 Insoluble complexes with the ratio arene Hg2+ = 1 1 (arene = benzene, naphthalene, 2-methylnaphthalene, 2,6-dimethylnaphthalene, acenaphthene, fluor-anthrene, phenanthrene, anthracene, 9,10-dimethylanthracene or 1,3-dinitrobenzene) or 1 2 (arene = 9,10-benzophenanthrene) have been characterized by elemental analysis and, in some cases, by Raman spectrometry.113,120 The 13CNMR data allow the estimation of formation constants for the hexamethylbenzene, p-xylene and 1,4-dichlorobenzene complexes together with the chemical shifts for the bound substrates in these cases.121 Probably the coordination compounds of dimercury(I) salts with carbazole, dibenzofuran and diben-zothiophene are also n complexes.122... 

ETS-10 is a thermally stable titanosilicate molecular sieve with potential for application in catalysis and adsorption. The as-synthesized Si/Ti ratio is 5. Methods for modification of the Si/Ti of ETS-10 are described. The resulting materials are characterized by elemental analysis, XRD, NMR, IR and raman techniques. These modified sieves show catalytic activity for oxidation of organic substrates with peroxide. 

Full kinetic characterization for mechanism-based inhibition can be a challenge. Not only are there multiple rates to determine, but the mechanism of inhibition is often a combination of several different steps. The dividing line between alternate substrate inhibitors and the more eom-plex suicide inhibitors is often blurred, with some alternate substrates being virtually irreversible and some suicide substrates with high partition ratios and a significant alternate substrate element of inhibition. The following examples describe the characterization of an alternate substrate inhibitor and a suicide inhibitor of the serine protease human leukocyte elastase. 

De Neve et al. (2000) have carried out a feasibility study to investigate the possibilities and limitations of CPAA as a thin layer characterization method (rather than for the determination of elemental concentrations in bulk samples). The required experimental conditions are (a) that the surface layer containing the analyzed element is thinner (1 pm or less) than the range of the charged particles used and (b) that the substrate (i.e. the layer on which the thin layer is deposited) does not contain the element(s) to be analysed. 

The experimental approach discussed in this article is, in contrast, particularly amenable to investigating solvent contributions to the interfacial properties 131. Species, which electrolyte solutions are composed of, are dosed in controlled amounts from the gas phase, in ultrahigh vacuum, onto clean metal substrates. Sticking is ensured, where necessary, by cooling the sample to sufficiently low temperature. Again surface-sensitive techniques can be used, to characterize microscopically the interaction of solvent molecules and ionic species with the solid surface. Even without further consideration such information is certainly most valuable. The ultimate goal in these studies, however, is to actually mimic structural elements of the interfacial region and to be able to assess the extent to which this may be achieved. 

P-gp substrate 64 substrates Different sources P-gp substrates characterized by well-defined sets of H-bond acceptor elements (type I and type II units). Strength and number of H-bond [40]... 

Of the protein kinases, protein kinase A is the best investigated and characterized (review Francis and Corbin, 1994). The functions of protein kinase A are diverse. Protein kinase A is involved in the regulation of metabolism of glycogen, lipids and sugars. Substrates of protein kinase A may be other protein kinases, as well as enzymes of intermediary metabolism. Protein kinase A is also involved in cAMP-stimulated transcription of genes that have a cAMP-responsive element in their control region (review Montminy, 1997). An increase in cAMP concentration leads to activation of protein kinase A which phosphorylates the transcription factor CREB at Ser 133. CREB only binds to the transcriptional coactivator CBP in the phosphorylated state and stimulates transcription (see Chapter 1.4.4.2). 

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