Affinity factor

The partition coefficient St of an ionic species i between a uniformly charged membrane and an aqueous solution may be analyzed into electrical and (apparent) chemical affinity factors X and K( respectively 107)... 

To account for the fact that Ci apparently has a much greater affinity for crystalline cellulose than Cx, we suggest that while Cx action causes the first cleavage of the glucosidic linkage, Ci is actually already in position awaiting the approach of Cx. In other words, Ci is an affinity factor, but it is different from that envisaged by Leatherwood in that it is also involved in the hydrolytic process. 

Since essentially all of the protein in the cellulose-grown culture or the sophorose-incubation mixture can be accounted for by the three principal proteins and the / -glucosidase, it seems reasonable to conclude that the multiplicity of enzymes seen after several days of culture growth are caused by degradation. This may be attributable either to inherent instability (3) or to the presence of hydrolytic enzymes (16). There seems to be no evidence for the Ci enzyme as a nonhydrolytic or affinity factor, since all known enzymes of the system are hydrolytic. That the sophorose-stimulated system (with no possible loss of the Ci ... 

Table 2. Data of the thermal expansion coefficient a (Kh K ), affinity factor and molar volume of the hquid-hke adsorbate, Vm (cm mol )-...

P is thus constant and called the affinity factor of adsorbate 2 (adsorbate 1 being considered as a the reference)... 

Dioxins and other substances (e.g. planar PCB congeners) with affinity for the Ah-receptor give rise to additive toxicity in proportion to the degree of affinity and action on the receptor. Thus, the different congeners are characterized by an affinity factor, the toxic equivalent factor (TEF), which, by multiplication with the actual concentration, gives the toxicity equivalent (TEQ) for the substance. In this context, the TEF of TCDD is set to unity and other substances have TEF < 1. By summing up the contributions or TEQs for all the congeners of PCDDs, PCDFs, PCBs, etc. involved, the total toxic impact on the Ah-receptor can be quantified (Paasivirta, 1991). 

We propose a new mechanism for cellulose degradation that is based on the formation of the cellulase complex and is compatible with the results reported in the scientific literature. An affinity factor and a hydrolytic factor are necessary for the formation of a complete cellulase which can hydrolyze native cellulose to cellobiose (Figure 2). The amount of affinity factor (xA) that combines with hydrolytic factor (yH) probably is not x = y = 1. This new mechanism does not require a separate enzyme for the formation of reactive cellulose. The natural... 

This mechanism could be unique for these anaerobic bacteria, however, the major findings reported in the literature are compatible with this proposal. Ci enzyme (3, 4) requires the addition of Cx, a hydrolytic factor, in order to effectively demonstrate activity. It may be that the Ci component is an affinity factor that binds the hydrolytic factor, Cx, to the insoluble cellulose. 

Figure 2. A new mechanism for cellulose degradation proposes the combination of affinity factor and hydrolytic factor to form a complete cellulase complex which can hydrolyze native cellulose to cellobiose...

Leatherwood Probably the classical protein-protein interaction is an antigen antibody reaction, in which two proteins interact to form a complex. And it is well known that excess concentration of one of these can interfere with the precipitin reaction. So, whenever you test affinity factors and hydrolytic factors, you must test at various levels. This would be one reason for overlooking the interaction. We have found an increase in adsorption of hydrolytic factor, by addition of it to solutions that had what we considered excess affinity factor. ... 

The above discussion provides some indication of how kinetic and affinity factors may interact in competitive situations. The more complex problem of how to synthesize all of the possible factors into a quantitative predictive model of competitive adsorption remains to be solved and is certainly worthy of considerable effort. Data for such models are currently unavailable. They could be obtained in two ways. First it may be assumed that affinity constants in single protein systems could be measured and with a knowledge of diffusion coefficients could be used to predict adsorption layer compositions in mixtures. This approach may have some validity at low surface concentrations but ignores the effect of interlayer interactions at higher coverages. 

Few cases are known where a metal-binding agent is, of itself, highly injurious to an organism. Thus oxine 11.30) can enter the cells of bacteria and fungi without apparent injury (see Section 11.7.1). Such freedom from damage arises from the normal steric and affinity factors which allowed the active site to accumulate and retain the metal. 

Since two hydrates of different binding energy play a part, the isotherm should represent a superposition of two Langmuir isotherms with a different value of the affinity factor, a large one for the first hydrate and a small one for the second hydrate. From an investigation of Matthes it can be deduced that the sorption isotherm of regenerated cellulose can be quantitatively accounted for on this basis up to a relative humidity of abound 65%. Matthes showed that (pi— — 2) should be linear in p (where pi, a ... 

Stronger binding affinity.Factor XII is activated to factor Xlla in the Vroman layer which marks the initiation of the Contact Activation Pathway. Activated factor Xlla converts factor XI to active factor XIa, which in turn activates factor IX to factor IXa. Factor IXa, along with factor VIII, activates factor X to factor Xa. This is the last step of the intrinsic pathway, which is the same as that in the extrinsic pathway. ... 

We shall call Sj the affinity factor of step j. Instead of (110) we now have... 

Cases of mechanisms involving steps with affinity factors of the same order of magnitude as that of the rate-determining step can also occur. We shall see that cases in point are certain types of hydrogen overtension mechanisms. 

It has been a constant pursuit of chemists to classify the elements in terms of such an affinity factor, in order to predict details of their interaction. The discovery of the periodic table provided the first clue towards identification of such a chemicalbonding parameter, which later became known as electronegativity. On plotting Lothar-Meyer atomic volumes as a function of atomic number, the elements are divided into two kinds, according to the local slope of the connecting curve [35]. This observation led to the classification into electropositive and electronegative elements. 

The ECT model has been little used in the analysis of gas-phase ion chemistry. In contrast, the ECW model is generally found helpful in many fields of solution chemistry and biochemistry, as shown in several reviews [77, 173, 177-179] and in a book [6] and by its introduction in many textbooks of (mainly inorganic) chemistry (e.g. ref. [180]). The ECW model is particularly useful for showing that there is no inherent one-parameter order of Lewis affinity. Factoring and rearranging Equation 1.121 (with W = 0) lead to [179]... 

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