XPS and FTIR characterization of manganese ions deposited on alumina

Cataloged from PDF version of article.By application of XPS and FTIR spectroscopy of adsorbed CO the effect of preparation conditions on the state and localization of manganese ions deposited on h-Al2O3 is studied. Both Mn21 and Mn31 ions are observed on the impregnated sample. The sample obtained by ion exchange contains only Mn31 ions. The adsorbed CO species are identified. q 1999 Elsevier Science B.V. All rights reserved

Spectroscopic investigation of species arising from CO chemisorption on titania-supported manganese

Cataloged from PDF version of article.The nature of manganese species on the surface of TiO2 (anatase) has been investigated by means of XPS, visible absorption spectroscopy, and FTIR spectroscopy of adsorbed CO. The catalysts were prepared by ion-exchange from aqueous manganese(II) chloride solution and impregnation. The application of ion-exchange results in a loading of manganese oxide phase corresponding to a monolayer coverage. On the surface of the ion-exchanged sample two kinds of Mn3+ ions are stabilized, differing in their coordinative saturation and localization. The Mn3+ ions form two kinds of linear carbonyls characterized by absorption at 2194 and 2187 cm−1 , respectively. The impregnated catalyst contains a mixture of Mn3+ and Mn2+ species. The latter ions produce a carbonyl band at 2114 cm−1 . The adsorption of CO at room temperature on the catalysts studied results in formation of formate, carbonate, and hydrogen carbonate structures as well. It is found that the formation of formate species is associated with the Mn3+ ions and the possible mechanism is discussed. The stabilization of the hydrogen carbonates is favored by Mn2+ ions. The reduction of the catalyst studied with hydrogen strongly suppresses the adsorption of CO and is indicative of the occurrence of a strong metal–support interaction. (c) 2000 Academic Pres

XPS and IR characterization of manganese ions deposited on alumina

Abstract By application of XPS and FTIR spectroscopy of adsorbed CO the effect of preparation conditions on the state and localization of manganese ions deposited on h-Al 2 O 3 is studied. Both Mn 2ϩ and Mn 3ϩ ions are observed on the impregnated sample. The sample obtained by ion exchange contains only Mn 3ϩ ions. The adsorbed CO species are identified. ᭧ 1999 Elsevier Science B.V. All rights reserved

Computational Insights into Dynamics of Protein Aggregation and Enzyme–Substrate Interactions

In this Perspective, the roles of protein dynamics have been discussed in the aggregation of amyloid beta (Aβ) peptides and formation of enzyme-substrate complexes of beta-secretase (BACE1) and insulin-degrading enzyme (IDE). The studies regarding the influence of individual amino acid residues and specific regions on the structures and oligomerization of early Aβ aggregates and computations of their translational and rotational diffusion coefficients and order parameters exhibited that even the short-time-scale molecular dynamics simulations can reproduce certain experimental parameters with reasonable accuracy. The simulations elucidating the enzyme-substrate interactions of BACE1 and IDE successfully showed that the chemical nature and length of the substrates influence the dynamics and plasticity of both the enzyme and substrate. An atomic-level understanding of these processes will advance our efforts to develop therapeutic strategies for several deadly diseases through the design of small molecules with antiaggregation properties and substrate-specific "designer" forms of enzymes