Existence of multiple states

For GAOX, structural analysis is particularly complicated, because of the existence of multiple states of the enzyme differing essentially only in the number of electrons, i.e., the oxidation state of the metalloprotein complex. Three distinct oxidation states can be prepared, each with properties and reactivities dramatically different from the others, as indicated in Fig. 10 (Whittaker and Whittaker, 1988). When isolated from culture medium, GAOX is a mixture of two of these states a blue, one-electron reduced, catalytically inactive form (lAGO) that contains a Cu(II) ion and no radical and a green form that is catalytically active (AGO) and contains both Cu(II) and a free radical. The enzyme may be converted to... 

Although the above models would explain qualitatively the observed multiple adsorption states, there is currently no fundamental treatment to predict such bonding. The possible existence of multiple states deserves attention for other adsorbents as well, including carbonaceous species. The potential dependence of such adsorbed states could explain reactivity and specificity of some reactants. 

Finally, a statistical argument for the existence of multiple states of adsorbed molecules can be made. Chemical species are thought to exist in a series of states governed by a probability function that is related... 

Evidence for Multiple States of Adsorbed.Proteins. The evidence to be reviewed here supporting the existence of multiple states of adsorbed proteins derives from many types of studies (see Table III). In each study, different techniques were used to study the behavior of proteins at interfaces but none was specifically designed nor applied to investigate the possible existence of multiple states of adsorbed proteins. Furthermore, the proteins, surfaces, and objectives of each study varied. Nonetheless, this diverse data base is consistent in support of the existence of multiple states, and its diversity may therefore actually provide greater... 

Theories of electron mobility are intimately related to the state of the electron in the fluid. The latter not only depends on molecular and liquid structure, it is also circumstantially influenced by temperature, density, pressure, and so forth. Moreover, the electron can simultaneously exist in multiple states of quite different quantum character, between which equilibrium transitions are possible. Therefore, there is no unique theory that will explain electron mobilities in different substances under different conditions. Conversely, given a set of experimental parameters, it is usually possible to construct a theoretical model that will be consistent with known experiments. Rather different physical pictures have thus emerged for high-, intermediate- and low-mobility liquids. In this section, we will first describe some general theoretical concepts. Following that, a detailed discussion will be presented in the subsequent subsections of specific theoretical models that have been found to be useful in low- and intermediate-mobility hydrocarbon liquids. 

The phase transitions for 90 were also evident in the UV-VIS spectra, as seen in Figure 26 M has an absorption maximum at 315 nm, QM at 350 nm, and multiple absorptions with peaks at ca. 315, 350, 365, and 378 nm are evident for phase I and the other phases. Isosbestic points observed between the phases indicate coexistence of two states during structural evolution, and the existence of multiple UV peaks for a phase is considered to indicate the existence of several conformations for that phase. In this report, 0 all structures were modeled with conformations between all-T and all-D thus, the conformational nature of the different phases of (Si-/z-Dec2U is not clear. Similar UV absorptions observed for structurally related polymers, such as PDHS (see below), are suggestive of comparable backbone conformations. 

It has been commonplace in chemical reaction engineering circles, since Luss first discovered the reference, that Liljenroth (1918) was the first to mention the existence of multiple steady states and the associated stability... 

In a chemical packed-bed reactor in which a highly exothermic reaction is taking place conditions may be encountered under which, for a given set of input conditions (feed rate, temperature, concentration), the exit conversion is either high or low. To the experimental study of conditions connected with the existence of multiple steady states in packed catalytic reactors has not been paid as much attention in the past as to the study of... 

In addition to openness and feedback, a third condition is often found in conjunction with oscillation, though it has not yet been proven to be necessary the existence of multiple stationary states. Most chemists are aware of the steady state condition, wherein the rate of change of the concentration of an intermediate can be equated to zero. Thus, the concentration of this intermediate can be obtained by solving an algebraic, rather than a differential equation. The familiar solution to this equation is a single concentration for a given set of initial conditions. [The reader may be familiar with a mechanism k k... 

Carbon Monoxide Oxidation. Analysis of the carbon monoxide oxidation in the boundary layer of a char particle shows the possibility for the existence of multiple steady states (54-58). The importance of these at AFBC conditions is uncertain. From the theory one can also calculate that CO will bum near the surface of a particle for large particles but will react outside the boundary layer for small particles, in qualitative agreement with experimental observations. Quantitative agreement with theory would not be expected, since the theoretical calculations, are based on the use of global kinetics for CO oxidation. Hydroxyl radicals are the principal oxidant for carbon monoxide and it can be shown (73) that their concentration is lowered by radical recombination on surfaces within a fluidized bed. It is therefore expected that the CO oxidation rates in the dense phase of fluidized beds will be suppressed to levels considerably below those in the bubble phase. This expectation is supported by studies of combustion of propane in fluidized beds, where it was observed that ignition and combustion took place primarily in the bubble phase (74). More attention needs to be given to the effect of bed solids on gas phase reactions occuring in fluidized reactors. 

In high resistivity GaN films, Glaser and co-workers observed ODMR on a broad band peaked at 3 eV and observed a second deep donor state at g = 1.978 [29]. Because the g value is between the effective mass donor and that of the first deep donor, they argued that the energy level was shallower than the first deep donor. Koschnick and co-workers [30] have also resolved a donor resonance atg - 1.96 in undoped fihns and a possibly different donor (also at g 1.96) in Mg-doped fihns using high frequency (70 GHz) ODMR. The existence of multiple donor levels was first proposed by Gotz and co-workers [31] based on their electrical measurements and these results seem to confirm that idea. 

Spectroscopic studies have consistently demonstrated the existence of multiple conformational states for the metal sites in transferrins, especially when using metal ions other than Fe3+ and anions other than C032. The differences are not necessarily related to intrinsic geometrical differences between the two sites in each molecule, but also reflect changes dependent on pH, the nature of the synergistic anion, or salt effects. 

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