Mono-nuclear model

A mono-nuclear model, which allows only one nucleation, the next nucleation taking place only after the entire surface is covered by growth layers originating from the earlier nucleus. 

It should be added that MS-02 is not necessarily a mono-nuclear complex. It could be shown in a few cases that the catalytic activity of the metal ion is due to the formation of dinuclear metal-substrate complexes. Presumably in these species each oxygen atom of dioxygen coordinates to a different metal center. Such systems were extensively used to model the reactivity patterns of various enzymes containing a bimetallic active center. 

The models proposed for the Ru(III) and Ru(EDTA) catalyzed epoxidation of allyl alcohol replace each other in the corresponding reactions of cyclohexene. Thus, mono-nuclear and di-nuclear paths were reported for the Ru(III) and Ru(EDTA) catalysis, respectively (145,146). 

We have performed a comparison of the design of the three families of mono-nuclear Mo oxo-transfer enzymes. In this study, we tried to understand why the active sites are so different in these three groups and what is the functional significance of these differences. Such questions are hard to answer by experimental techniques. Even if the three types of aetive sites could be constructed in the same enzyme by mutational methods, it would be uncertain whether the obtained results were caused by the intrinsie preferences of the active sites, or by differences in the stability of the mutated enzymes or the binding of substrates and products to the proteins. However, with QM-cluster models, we can easily obtain pure estimates of the intrinsic preferences of the various types of Mo sites. Similar studies have also been performed with other types of metal sites in proteins, e.g. tetrapyrroles, electron-transfer sites and hydrogenases. ... 

For two and three dimensions, it provides a crude but useful picture for electronic states on surfaces or in crystals, respectively. Free motion within a spherical volume gives rise to eigenfunctions that are used in nuclear physics to describe the motions of neutrons and protons in nuclei. In the so-called shell model of nuclei, the neutrons and protons fill separate s, p, d, etc orbitals with each type of nucleon forced to obey the Pauli principle. These orbitals are not the same in their radial shapes as the s, p, d, etc orbitals of atoms because, in atoms, there is an additional radial potential V(r) = -Ze2/r present. However, their angular shapes are the same as in atomic structure because, in both cases, the potential is independent of 0 and (f>. This same spherical box model has been used to describe the orbitals of valence electrons in clusters of mono-valent metal atoms such as Csn, Cu , Na and their positive and negative ions. Because of the metallic nature of these species, their valence electrons are sufficiently delocalized to render this simple model rather effective (see T. P. Martin, T. Bergmann, H. Gohlich, and T. Lange, J. Phys. Chem. 95, 6421 (1991)). 

For the visualization and localization of single NPC cells are grown in mono-layer culture. Cells are permeabilized such that the plasma membrane becomes permeable to antibodies while the nuclear envelope and the NPC remains intact. The NPC is labeled with a primary antibody that is specific for an NPC protein. This is followed by reaction with a second fluorescently labeled antibody. The subsequent acquisition of stacks of high-resolution confocal images as well as the localization of single NPCs closely follows the procedure described for the model system. The final result of the procedure is illustrated in Fig. 3a (see color plate). 

The metal carbonyl clusters - They have been characterized by X-ray diffraction with nuclearities up to the range 30 to 40, by the pioneering work of Chini. They are neutral or, mono-, di-, or trianionic, and these anions can be protonated to give respectively mono-, di- or trihydrides. They have been much studied by organometallic chemists who have used them as models of the Fischer-Tropsch reaction and replaced some carbonyls by unsaturated hydrocarbon ligands. Wade has compared them to metalloboranes, which allowed him to propose a new, correct electron count. Metallocarboranes, derived from the latter, were introduced by Hawthorne. 

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