Activity segment molar

Finally, segment-molar activity coefficients Ta and fa, are introduced to describe all deviations from the Flory-Huggins mixture (with x = 0). Within the continuous treatment the segment-mole fraction Vb, will be replaced by [29]... 

Further treatment depends on how the distribution function WB(rB, Y ) influences the segment-molar activity coefficients f and fg and the segment-molar excess Gibbs free energy G . In the most general case, G may be a functional of WjfrB, Yb) itself, and the unknown scalar ipg and the unknown distribution function WB(rB, Yg) are coupled in complicated ways, because QB(rB, Yg) in Eq. (39) contains depending on the unknown distribution function Wg(rg, Yg). 

No special reference is made here to the methods which calculate the segment-molar activity coefficients for the general case treated in this chapter, because the general expressions are given by Eqs. (18) and (19). All special details depend on the G -model to be applied and the details in which this model is influenced by moments of the distribution function. The principal way of taking different moments into account is given by Eqs. (54)-(61), which may analogously be extended to the case of more moments. 

With Eqs. (62), (64) and (81), the segment-molar activity coefficients are given by... 

The segment-molar activity coefficients now read (generalizing Eqs. (82) and (83))... 

The segment-molar activity coefficients have to be expressed by two terms. 

The influence of the chemical composition in (5) can be derived using a simplified versicai of Barker s lattice theory [55], The most important consequence of (5) is the fact that the segment-molar excess Gibbs free energy of mixing and, hence, the activity coefficients depend only oti the average value (yw) of the distribution function, but not on the distribution function itself. In continuous thermod5mamics, the phase equilibrium conditions read ... 

The activity coefficients in (9) can be derived using standard thermodynamics in combination with (5). The replacement of the segment-molar chemical potential of the copolymer species in (7) according (4) leads to ... 

When the molar ratio of pepstatin/pepsinogen was 0.9 1, the composition of the crude peptides obtained was much more similar to the expected composition from residues 1-44 (Table IV). Several NH2-termini were obtained similar to the result obtained on activation of pepsinogen in the absence of pepstatin. Presumably the pepstatin inhibits 90% of the activating pepsinogen but the remaining 10% can convert itself all the way into pepsin. This active pepsin could then split off the remaining activation segments exposed on the inhibited molecules so that a mix of 90% inhibited pepsin plus 10% active pepsin is obtained. 

A direct effect of luminal lipids on the absorption of bile salts has been found by Sklan and Budowski [75], Taurocholate uptake was determined in situ in segments of rat small intestine, and jejunal absorption increased when taurocholate was injected together with oleic acid, monoolein, PC or lyso-PC. For each lipid a certain molar ratio of lipid to bile salt was found that resulted in an optimal uptake of taurocholate. In contrast, the active uptake of bile salts by isolated intestinal villi preparations of hamster distal ileum has been found to be inhibited by dietary lipids [76]. 

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