Characterization of NOx species in dehydrated and hydrated Na- and Ba-Y, FAU zeolites formed in NO2 adsorption

Adsorbed ionic NO_x species formed upon the interaction of NO₂ with dehydrated or hydrated Na- and Ba-Y, FAU zeolites were characterized using FT-IR/TPD, solid state NMR, and XANES techniques. NO₂ disproportionates on both dehydrated catalyst materials forming NO⁺ and NO₃⁻ species. These ionic species are stabilized by their interactions with the negatively charged zeolite framework and the charge compensating cations (Na⁺ and Ba²⁺), respectively. Although the nature of the adsorbed NO_x species formed on the two catalysts is similar, their thermal stabilities are strongly dependent on the charge compensating cations. In the presence of water in the channels of these zeolite materials new paths open for reactions between NO⁺ and H₂O, and NO₂ and H₂O, resulting in significant changes in the adsorbed ionic species observed. These combined spectroscopic investigations afforded the understanding of the interactions between water and NO₂ on these zeolite catalysts.     

Adsorption, desorption, and clustering of H2O on Pt111

The adsorption, desorption, and clustering behavior of H2O on Pt111 has been investigated by specular He scattering. The data show that water adsorbed on a clean Pt111 surface undergoes a structural transition from a random distribution to clustered islands near 60 K. The initial helium scattering cross sections as a function of temperature are found to be insensitive to the incident H2O flux over a range of 0.005 monolayers (ML)/s-0.55 ML/s indicating that the clustering process is more complex than simple surface diffusion. The coarsening process of an initially random distribution of water deposited at 25 K is found to occur over a broad temperature range, 60相似文献   

Low temperature H2O and NO2 coadsorption on theta-Al2O3/NiAl(100) ultrathin films

The coadsorption of H(2)O and NO(2) molecules on a well-ordered, ultrathin theta-Al(2)O(3)/NiAl(100) film surface was studied using temperature programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS), and X-ray photoelectron spectroscopy (XPS). For H(2)O and NO(2) monolayers adsorbed separately on the theta-Al(2)O(3)/NiAl(100) surface, adsorption energies were estimated to be 44.8 and 36.6 kJ/mol, respectively. Coadsorption systems prepared by sequential deposition of NO(2) and H(2)O revealed the existence of coverage and temperature-dependent adsorption regimes where H(2)O molecules and the surface NO(x) species (NO(2)/N(2)O(4)/NO(2)(-),NO(3)(-)) form segregated and/or mixed domains. Influence of the changes in the crystallinity of solid water (amorphous vs crystalline) on the coadsorption properties of the NO(2)/H(2)O/theta-Al(2)O(3)/NiAl(100) system is also discussed.     

Water-induced morphology changes in BaO/gamma-Al2O3 NOx storage materials

Exposure of NO(2)-saturated BaO/gamma-Al(2)O(3) NO(x) storage materials to H(2)O vapour results in the conversion of surface nitrates to Ba(NO(3))(2) crystallites, causing dramatic morphological changes in the Ba-containing phase, demonstrating a role for water in affecting the NO(x) storage/reduction properties of these materials.     

The measurement of chemiluminescence,aggregation, and 5-hydroxy-6,8,11,14-eicosatetraenoic acid production of n-formyl-methioninyl-leucyl-phenylalanine-stimulated human polymorphonuclear leukocytes

Polymorphonuclear leukocytes (PMNs) which had been treated with nordihydroguaiaretic acid (NDGA) or indomethacin were stimulated with varying doses of n-formyl-methioninyl-leucyl-phenylalanine (FMLP). Aggregation and chemiluminescence (CL) were simulta-neously measured. Supernatant solutions were obtained and saved from cells stimulated with 10^?6M FMLP. These solutions were assayed for 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) using radioimmunoassay (RIA) techniques and used as a measure of 5-lipoxygenase (LO) activity. It was found that 10^?5M NDGA inhibited CL from PMNs stimulated with FMLP. However, NDGA had much less effect on aggregation of these cells. Indomethacin had little effect on PMN aggregation and less effect on CL than NDGA following FMLP stimulation. Indomethacin (10^?5M) did inhibit CL stimulated with FMLP at FMLP doses of 10^?7 and 10^?6M but had no effect of CL at FMLP doses of 10^?5M. Finally, RIA for 5-HETE showed that the effects of NDGA and indomethacin on 5-HETE production could be correlated with their effects on CL responses of cells stimulated with 10^?6M FMLP. These results support two conclusions. First, PMN-CL and LO activity may be correlated. Second, PMN-CL is not necessarily associated with PMN aggregation. These observations may indicate that LO products are not necessary for PMN aggregation to occur.     

Mass spectrometric detection for capillary isoelectric focusing separations of complex protein mixtures

Capillary isoelectric focusing (CIEF) can provide high-resolution separations of complex protein mixtures, but until recently it has primarily been used with conventional UV detection. This technique would be greatly enhanced by much more information-rich detection methods that can aid in protein characterization. We describe progress in the development of the combination of CIEF with Fourier transform ion cyclotron resonance (FTICR) mass spectrometry and its application to proteome characterization. Studies have revealed 400-1000 putative proteins in the mass range of 2-100 kDa from total injections of approximately 300 ng protein in single CIEF-FTICR analyses of cell lysates for both Escherichia coli (E. coli) and Deinococcus radiodurans (D. radiodurans). We also demonstrate the use of isotope labeling of the cell growth media to improve mass measurement accuracy and provide a means for quantitative proteome-wide measurements of protein expression. The ability to make such comprehensive and precise measurements of differences in protein expression in response to cellular perturbations should provide new insights into complex cellular processes.     

A novel method for measuring initial-burst chemiluminescence in a liquid scintillation counter using the myeloperoxidase-H20Cl− reaction

These studies show that there is an initial quantifiable burst of luminol-enhanced CL associated with the interaction of MPO with H₂O₂ and Cl^?. They also confirm that the reaction is H₂O₂-concentration dependent (2). The novel method for quantifying initial-burst CL in a liquid scintillation counter introduced in this study provides many advantages over previous CL studies using the same counter, as noted above. This method provides for more efficient representation of CL associated with the MPO reaction, and allows for valid conclusions concerning the drug effects on this reaction. The ability to “see” the initial part of the reaction may also allow kinetic analysis of this (and other) enzyme CL reactions.