273 resultados para Sphere Redox Reactions
Resumo:
In last 30 years innovative research in the area of auto exhaust catalysis is being developed and CeO2 has been found to play a major role in this area due to its unique redox properties. In this review, auto exhaust emission and its impact on earth’s environment, global concern and recent advances in science and technology in automotive exhaust catalysis have been documented. A new preparative method of dispersing metal ions by solution combustion technique over CeO2 and TiO2 resulting mainly Ce1−xMxO2−δ, Ti1−xMxO2−δ and Ce1−x−yTixMyO2−δ (M = Pd, Rh and Pt) catalysts, structure of these materials, their catalytic properties towards auto exhaust catalysis, structure–property relation and mechanism of catalytic reactions are accounted here. In these materials, metal ions are incorporated into substrate matrix to a certain limit in the solid solution form and we have established a new direction in heterogeneous catalysis by turning to the concept of dispersed metal ions as catalytically active sites from the conventionally nurtured idea of metal particles as active centers for catalysis.
Resumo:
Protein-protein interactions are crucial for many biological functions. The redox interactome encompasses numerous weak transient interactions in which thioredoxin plays a central role. Proteomic studies have shown that thioredoxin binds to numerous proteins belonging to various cellular processes, including energy metabolism. Thioredoxin has cross talk with other redox mechanisms involving glutathionylation and has functional overlap with glutaredoxin in deglutathionylation reactions. In this study, we have explored the structural and biochemical interactions of thioredoxin with the glycolytic enzyme, triosephosphate isomerase. Nuclear magnetic resonance chemical shift mapping methods and molecular dynamics-based docking have been applied in deriving a structural model of the thioredoxin-triosephosphate isomerase complex. The spatial proximity of active site cysteine residues of thioredoxin to reactive thiol groups on triosephosphate isomerase provides a direct link to the observed deglutathionylation of cysteine 217 in triosephosphate isomerase, thereby reversing the inhibitory effect of S-glutathionylation of triosephosphate isomerase.
Resumo:
Protein−protein interactions are crucial for many biological functions. The redox interactome encompasses numerous weak transient interactions in which thioredoxin plays a central role. Proteomic studies have shown that thioredoxin binds to numerous proteins belonging to various cellular processes, including energy metabolism. Thioredoxin has cross talk with other redox mechanisms involving glutathionylation and has functional overlap with glutaredoxin in deglutathionylation reactions. In this study, we have explored the structural and biochemical interactions of thioredoxin with the glycolytic enzyme, triosephosphate isomerase. Nuclear magnetic resonance chemical shift mapping methods and molecular dynamics-based docking have been applied in deriving a structural model of the thioredoxin−triosephosphate isomerase complex. The spatial proximity of active site cysteine residues of thioredoxin to reactive thiol groups on triosephosphate isomerase provides a direct link to the observed deglutathionylation of cysteine 217 in triosephosphate isomerase, thereby reversing the inhibitory effect of S-glutathionylation of triosephosphate isomerase.
Resumo:
A solvent-free synthesis of alpha-aminonitriles and beta-nitroamines by oxidative cross-dehydrogenative coupling under aerobic condition is reported. A catalytic amount of molybdenum(VI) acetylacetonoate was found to catalyze cyanation of tertiary amines to form alpha-aminonitriles, whereas vanadium pentoxide was found to promote aza-Henry reaction to furnish beta-nitroamines. Both of these environmentally benign reactions are performed in the absence of solvents using molecular oxygen as an oxidant.
Resumo:
In this paper, the synthesis and characterization of some imidazole-based gold-selenolates are described. This study indicates that the nature of selenolate plays an important role in ligand exchange reactions in gold(I) selenolates. Furthermore, the reactivity of imidazole-based gold(I) selenolates toward nucleophiles such as selenols and phosphines is strikingly different from that of the N,N-dimethylaminobenzylamine-based gold(I) complexes. The presence of Se ... N non-bonded interactions in N,N-dimethylaminobenzylamine-based gold(I) complexes modulates the reactivity of Au(I) centre towards incoming nucleophiles.
Resumo:
Dendrimers are ideal platforms to study multivalent effects due to the presence of uniform end groups at their peripheries. This report concerns with a study of multivalent dendritic catalysts, both within and across dendrimer generations, and their effects to mediate C-C bond forming reactions on multivalent substrates that have two and three acrylate reactive sites. As many as fourteen multivalent dendritic catalysts were prepared using 0-3 generations of poly(propyl ether imine) dendrimers, incorporated with Pd(II) catalytic sites, both within and across the dendrimer generations. C-C Bond forming reactions of these substrates with iodobenzene, mediated by uniform concentration of the metal across all catalysts, showed formation of partially and fully functionalized cinnamates in varying ratios, depending on the extent of clustering of catalytic moieties at the peripheries of dendrimers within a dendrimer generation. In a given generation, higher clustering of catalytic moieties greatly assisted multiple C-C bond formations than presenting the same in lesser number. The studies demonstrate true benefits of clustering catalytic moieties within a dendrimer generation and the beneficial effects applicable to catalysis of substrates presenting more than one reactive center. (C) 2011 Elsevier B.V. All rights reserved.
Resumo:
Scattering of water waves by a sphere in a two-layer fluid, where the upper layer has an ice-cover modelled as an elastic plate of very small thickness, while the lower one has a rigid horizontal bottom surface, is investigated within the framework of linearized water wave theory. The effects of surface tension at the surface of separation is neglected. There exist two modes of time-harmonic waves - the one with lower wave number propagating along the ice-cover and the one with higher wave number along the interface. Method of multipole expansions is used to find the particular solution for the problem of wave scattering by a submerged sphere placed in either of the layers. The exciting forces for vertical and horizontal directions are derived and plotted against different values of the wave number for different submersion depths of the sphere and flexural rigidity of the ice-cover. When the flexural rigidity and the density of the ice-cover are taken to be zero, the numerical results for the exciting forces for the problem with free surface are recovered as particular cases. (C) 2011 Elsevier Ltd. All rights reserved.
Resumo:
A variable resolution global spectral method is created on the sphere using High resolution Tropical Belt Transformation (HTBT). HTBT belongs to a class of map called reparametrisation maps. HTBT parametrisation of the sphere generates a clustering of points in the entire tropical belt; the density of the grid point distribution decreases smoothly in the domain outside the tropics. This variable resolution method creates finer resolution in the tropics and coarser resolution at the poles. The use of FFT procedure and Gaussian quadrature for the spectral computations retains the numerical efficiency available with the standard global spectral method. Accuracy of the method for meteorological computations are demonstrated by solving Helmholtz equation and non-divergent barotropic vorticity equation on the sphere. (C) 2011 Elsevier Inc. All rights reserved.
Resumo:
The use of the sulfurdiimide RN=S=NR' (R = R' = SiMe3, 3) in reactions with group 4 metallocene bis(trimethylsilyl)-acetylene complexes of the type [Cp2M(L (eta(2)-Me3Si-C2SiMe3)] (1: M = Ti, no L; 2: M = Zr, L = pyridine) has led to the formation of four-membered metallacycles 4M containing the group 4 metal, nitrogen and sulfur. DFT calculations performed on compound 4Ti indicate that this complex is best described as a sigma-complex with cyclic delocalisation of the ring electrons. Moreover, pseudo-Jahn-Teller distortion plays a significant role in stabilising this complex.