The Discrimination Factor

In the transport across a phospholipid bilayer by passive diffusion, the permeability of the neutral form of a molecule is 10X times greater than that of the charged form. For the epithelium, the discrimination factor is 105. The basement membrane (Fig. 2.5) allows passage of uncharged molecules more readily than charged species by a factor of 10 [76]. 

It is clear that above 15 kcal/mol, a region of saturation of the first-order electrostatic effect is entered, and a second-order effect can be discerned becoming the discriminating factor of hydrogen bond strength. 

It is also clear (e.g. from the inactive 4 position in quinoline) that there is in general no more justification for using 7Tr, by itself than for using g, it is only for alternant hydrocarbons that the self-polarizability is the discriminating factor, and in all other cases tt,, should be considered only to the extent that it modifies conclusions based on the leading term g Sa,. in (18). Moreover, the relative importance of the two terms depends on the value of 8[Pg.87]

It is important to consider the discrimination factor. People with dark skin may fail the urine test due to the false positive melanin. Drugs are detected easier in dark haired people when the hair test is used [Berns]. 

The discrimination factors a (a is the ratio of the two sorption equilibrium signals towards both enantiomers) of methyl lactate by R- and S-sensors and the a-1 values to demonstrate the inversion symmetry are shown in Fig. 6, right. The results are in complete accordance with gas chromatographic inves-... 

Fig. 20.8. Discrimination factor as a function of the initial kinetic energy of a fragment ion obtained by ion trajectory simulations. For the present simulations the ion source and the electrostatic lenses were treated fully three-dimensionally (see Fig. 20.1) and the maximum deviation from the real ion source was less than 5%. The dashed line represents the discrimination factors that were derived by Poll et al. [13] approximating the lenses infinitely long in the z-direction. The dash-dotted line are the discrimination factors that were derived in [34]. The potential array was more than a factor 10 smaller (less RAM of the computer) and thus the differences between simulation and reality were in the order of 15%...

Cr(C6Hii)4 is tetrahedral and a triplet however, square-planar discriminating factor. Another factor at work in these molecules is the spin pairing energies. As indicated previously, 3d valence orbitals are considerably more contracted that 4d and 5d thus the Coulomb repulsion integrals are much larger for first-row transition metal complexes and high-spin states are more favored than is the case for second and third row complexes. 

For systems not artificially enriched in (e.g., tracer experiments), the discrimination factor is essentially equal to the difference between the of the substrate... 

Log k, the intrinsic reactivity, varies from one reacting complex to another, as does s, the discrimination factor , but n° values are practically invarient with substrate. 

Quantitative determination of the relative contributions of sucrose synthase and invertase to the breakdown of phloem-supplied sucrose can be determined from the total metabolism rate for each sugar and the discrimination factor for the two sugars as substrates for invertase and sucrose synthase. The total rate of breakdown of either sucrose or 1 -FS is the sum of the fluxes through the two enzymes so that ... 

Fignre 16.1 Explanation of the discrimination factor dg. Measured is the ratio of the distance between the apex of the smaller peak and the valley to the height of the smaller peak... 

Since Jls is the fimtor that is most widely used to measure separation quality, it is worthwhile to compare it to the discrimination factor. For peaks exhibitiog the same height, and assuming that the observed retention times are very dose to the retention times of the individual components (22), the combination of Equations (16.6) and (16.14) leads to the following relationship ... 

Figure 16J Dependence of the resolution Rs on the discrimination factor do for different values of the relative peak height h .

The discrimination factor has also been used in error analysis in quantitative HPLC (22). Since resolution is not sensitive to relative p height and the error in quantitation depends strongly on the location of the valley between the peaks, do is a valid parameter for duuacterizing errors in quantitative analysis. The error can be expressed using the fractional area F, and fractional height for the smallest pe i (the one for which the error is the higliest) ... 

In this chapter, a series of research studies are presented as example of the above mentioned. Thus, with respect to the Sr, refer to section 2.1, the first paper deals with the discrimination factor between Ca/ Sr in absorption intestinal mechanisms. Afterwards, the different behavior of these metals in the binding to serum proteins is studied. And finally, the possibility of a hormonal regulation mechanism of serum levels of this element is evaluated, given the similarity of its biological behavior with the Ca. 

The used basic environment is the discriminating factor, here NaOH leaving with more free binding (and less porosity) potential for further interaction than NHj, most probably due to the OH group ability (reactivity) to be further involved (and therefore blocked) in the Si surface through the related vibrations and overtones combinations see Figure 4.8. 

Summarizing as follows, we could say that we learned the following from the thermodynamic studies (1) The different stability of the copper(H) ternary complexes with functionalized P-cyclodextrins is enthalpy driven, in accordance with what was previously found for the ternary system without the CD cavity (2) The cis-disposition of the amine groups of the two ligands seems to be the discriminating factor, in some cases allowing the interaction of the aromatic residues of one the two isomers with the cavity (3) The difference in AH° values between the two copper(II) diastereoisomeric complexes reflects the different interactions of the aromatic moieties of the two amino acid enantiomers. 

D-TLC). The 2D-TLC method has several increments to the elution-elution developments, such as the discrimination factors are different in the 1st and in the 2nd dimensional separations. The spots are concentrated through the 2nd dimensional development. Use of a spacer may further increase the separation of the spots that are located close to each other. Extensive work was devoted to the D-TLC using forced flow of the mobile phase (FFMP) " and to the comparison of the effect of forced flow of the mobile phase to that of the classical (capillary flow) TLC. ... 

For an early-phase project, the discrimination factor is usually equal to or greater than 0.5. However, for a late-phase project, it needs to be equal to or greater than 0.8 for high accuracy. 

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