Simple Inorganic Systems

TABLE 11 Bromine-79/81 solid-state spin-lattice relaxation (Ti) values for simple inorganic systems ... 

A number of studies have involved the doping of simple inorganic systems, followed by bromine NMR to determine the gradient-elastic tensor of various alkali halide crystals, which provides another way for determining the EFG tensor at the halogen site. Pulsed double-resonance experiments have also been used to establish the presence of impurity ions in alkali halide crystals. ... 

M., Dreyer, E., Devon, R., Schmoll, M., and Douthat, D. (2005) Spontaneous formation of chemical motors in simple inorganic systems. J. Mater. Sci., 40, 4671-4673. 

The pH optimum of an enzyme will often vary from one substrate to another and must be determined for each substrate. The buffer system used will often affect the overall activity of an enzyme and may alter its pH optimum. In general, the amino buffers such as glycylglycine and tricine, etc. (Table 8.2) result in a greater enzyme activity than do the simple inorganic buffers such as phosphate and carbonate. Buffers are most effective over a narrow pH range (approximately two units) which centres on their pK, value. Those buffers with pKa values similar to the known optimum pH of the enzyme should be tested for their effect on the activity of the enzyme over a limited pH range. 

Intuitively such delivery systems or excipients would best achieve this objective if they were to be composed of natural products or their modifications an overwhelming presence of excipients under this category (discussed in Ref. 1) provides credence to this observation. The substitution of natural products comprising complex proteins, antibodies, chimera, or toxins in lieu of stand-alone simple inorganic molecules as excipients for parenteral drug delivery represents a paradigm shift in the introduction of emerging excipients in the therapeutic armamentarium. 

Several reviews deal with the solid-state reactions of simple inorganic salts and of organic compounds.1-8 The essential differences between solid-state reactions and reactions in solution can be ascribed to the fact that solid-state reactions occur within the constraining environment of the crystal lattice. The reactant crystal lattice can control both the kinetic features of a reaction, and the nature of the products. In many solid-phase reactions the separation distances and mutual orientations of reactants in the solid determine the product. Such reactions are said to be topo-chemically controlled.9 Topochemical control of a reaction product is analogous to kinetic control in solution. The product is not necessarily the thermodynamically most stable product available to the system, but is rather the one dictated by the reaction pathway available in the constraining environment of the solid. 

The appearance of similar absorption bands has also been observed upon the formation of a complex between the reduced form of cytochrome c and the simple inorganic acceptor Fe(III)(CN)6[106]. The tunneling distance evaluated from the intensity of this band amounts to 7—10 A. However, more recent experiments have failed to detect such a band [107]. The situation is more favourable in the system [cytochrome c/P870] of the Chromatium reaction centre, where the intensity of the charge transfer band centred at 200 nm could be correlated with the data obtained in kinetic experiments [108]. 

In the following sections of this chapter, we consider water decomposing systems based on simple inorganic ions or complexes, and then those which involve multistep intermolecular electron... 

A final example concerns the formation of heteropolynuclear hydroxide complexes.116 The complexes [(OH)Fe(OH)2Cr]3+, [(OH)Fe(OH)2Cr(OH)]2+ and [(OH)2Fe(OH)2Cr(OH)]+, or polymers such as Fe(OH)2M "+ (M = V, Cr, Mn, Co, Ni, Cu n = 2-4) have been studied with a view to an understanding of the inclusion of transition metals in iron ores as mixed oxides rather than their occurrence as discrete mineral phases. Many other examples might have been chosen in this section. Reference should be made to the general reviews given above. However it should be clear that simple inorganic coordination complexes play a major role in the chemistry of natural aqueous systems at low temperatures. 

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