Thermodynamic affinity, for

In this chapter, the subscript 1 denotes the penetrant and subscript 2, the polymer. The term penetrant refers to solvents which have sufficient thermodynamic affinity for and interaction with the polymer. It is because of this interaction that penetrant diffusion exhibits a significant concentration dependence. This orientation excludes consideration of the permeation of small gaseous molecules. 

Thus, photoexcitation permits those electron transfer reactions to occur which are thermodynamicadly impossible in the dark, provided that the photon irradiation shifts the energy level of interfacial electrons (or holes) in the anodic (or cathodic) direction and produces the thermodynamic affinity for the reactions. 

The larger thermodynamic affinity for the aqueous medium for the case of normal complexes as compared to interface complexes (Figure 7.16a) correlates well with ( -potential values of oil droplets in mixed and bilayer emulsions (Table 7.3). 

Fligh-spin iron in a nonheme environment exhibits a significant change in the thermodynamics and kinetics of protein binding on reduction from Fe " to Fe ". This is illustrated by the mammalian serum iron-transport protein, transferrin. The thermodynamic affinity for Fe " is 10 in the presence of carbonate as a synergistic anion, and is reduced to 10 on reduction to Pg2-i- 21,22 jj-on-ligand turnover is also enhanced upon reduction. The net result is a non-Nernstian spectroelectrochemical response because of an elec-trochemically driven reduction followed by a coupled equilibrium dissociation of Fe " as illustrated in eqns (2.4) and (2.5) ... 

A nucleophile is a reagent which supplies an electron pair to form a new bond between itself and another atom (9). Swain and Scott (10) proposed that in describing properties of these species basicity be used solely in equilibria (thermodynamic) phenomena and nucleophilicity in rate (kinetic) phenomena. Parker (11) further suggested that the thermodynamic affinity for elements other than hydrogen be termed M-basicity, e.g., carbon basicity or sulfur basicity. 

The results of calculations show that the diffusion coefficients of DBS, DOA, and TO in PUU differ only a little. The diffusion coefficient of toluene is many times higher due to the fact that its molar volume V, is much smaller. Increase in D during swelling of polymer in toluene according to the previous data is also a natural consequence of the greater thermodynamic affinity for toluene to PUU comparing with other solvents. This can be seen from the values of parameter x i shown in Table 6.6.2. 

Gilson et al., 1997] Gilson, M., Given, J., Bush, B., and McCammon, J. The statistical-thermodynamic basis for computation of binding affinities A critical review. Biophys. J. 72 (1997) 1047-1069... 

In some metal components it is possible to form oxides and carbides, and in others, especially those with a relatively wide solid solubility range, to partition the impurity between the solid and the liquid metal to provide an equilibrium distribution of impurities around the circuit. Typical examples of how thermodynamic affinities affect corrosion processes are seen in the way oxygen affects the corrosion behaviour of stainless steels in sodium and lithium environments. In sodium systems oxygen has a pronounced effect on corrosion behaviour whereas in liquid lithium it appears to have less of an effect compared with other impurities such as C and Nj. According to Casteels Li can also penetrate the surface of steels, react with interstitials to form low density compounds which then deform the surface by bulging. For further details see non-metal transfer. 

By adding a third element (C) it is possible to increase the likelihood of forming compound BO, at a lower concentration than would be required in the pure binary alloy /4-B, provided that the third element C has an affinity for O intermediate between that of A and B" . If the mobility of B in the ternary alloy is high enough and element C has sufficient thermodynamic activity in the alloy to form CO, then the potential of O may be lowered to such an extent that BO forms more readily, i.e. element C acts as a getter for element B. Such behaviour is characteristic of, for instance, Fe-Al-Si and Fe-Cr-Si alloys. 

Thermodynamically it would be expected that a ligand may not have identical affinity for both receptor conformations. This was an assumption in early formulations of conformational selection. For example, differential affinity for protein conformations was proposed for oxygen binding to hemoglobin [17] and for choline derivatives and nicotinic receptors [18]. Furthermore, assume that these conformations exist in an equilibrium defined by an allosteric constant L (defined as [Ra]/[R-i]) and that a ligand [A] has affinity for both conformations defined by equilibrium association constants Ka and aKa, respectively, for the inactive and active states ... 

Individual liquids and elastomers each possess their own solubility parameter, 5. This is a thermodynamic property which is related to the energy of attraction between molecules. In its simplest form, an elastomer will possess a drive to absorb a liquid of similar 8, and be swollen by it. As the difference between the solubility parameter values of species increases, so their affinity for each other decreases. The commonest units for 8 in the literature are (cal cm ) / to convert values thus to MPa, multiply by 2.05. 

Table 3 presents the proton affinities calculated (without zero-point and thermodynamic contributions) for both N- and 0-ends of N2O. It is seen that indeed the SCF result leads... 

An inhibitor that binds exclusively to the ES complex, or a subsequent species, with little or no affinity for the free enzyme is referred to as uncompetitive. Inhibitors of this modality require the prior formation of the ES complex for binding and inhibition. Hence these inhibitors affect the steps in catalysis subsequent to initial substrate binding that is, they affect the ES —> ES1 step. One might then expect that these inhibitors would exclusively affect the apparent value of Vm and not influence the value of KM. This, however, is incorrect. Recall, as illustrated in Figure 3.1, that the formation of the ESI ternary complex represents a thermodynamic cycle between the ES, El, and ESI states. Hence the augmentation of the affinity of an uncompetitive inhibitor that accompanies ES complex formation must be balanced by an equal augmentation of substrate affinity for the El complex. The result of this is that the apparent values of both Vmax and Ku decrease with increasing concentrations of an uncompetitive inhibitor (Table 3.3). The velocity equation for uncompetitive inhibition is as follows ... 

Electrode potentials are determined by the affinities of the electrode reactions. As the affinities are changes in thermodynamic functions of state, they are additive. The affinity of a given reaction can be obtained by linear combination of the affinities for a sequence of reactions proceeding from the same initial to the same final state as the direct reaction. Thus, the principle of linear combination must also be valid for electrode potentials. The electrode oxidation of metal Me to a higher oxidation state z+>2 can be separated into oxidation to a lower oxidation state z+>1 and subsequent oxidation to the oxidation state z+>2. The affinities of the particular oxidation processes are equivalent to the electrode potentials 2 0, i-o> and E2-. ... 

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