Scaling parameters topological effect

The applicability of Eq. (45) to a broad range of biological (i.e., toxic, geno-toxic) structure-activity relationships has been demonstrated convincingly by Hansch and associates and many others in the years since 1964 [60-62, 80, 120-122, 160, 161, 195, 204-208, 281-285, 289, 296-298]. The success of this model led to its generalization to include additional parameters in attempts to minimize residual variance in such correlations, a wide variety of physicochemical parameters and properties, structural and topological features, molecular orbital indices, and for constant but for theoretically unaccountable features, indicator or dummy variables (1 or 0) have been employed. A widespread use of Eq. (45) has provided an important stimulus for the review and extension of established scales of substituent effects, and even for the development of new ones. It should be cautioned here, however, that the general validity or indeed the need for these latter scales has not been established. 

It is important for the theoretical understanding of the formation of various topologies that these aggregates have entropic contributions on the scale of the objects, i.e. on a much larger scale than set by the molecules. These cooperative entropic effects should be included in the overall Helmholtz energy, and they are essential to describe the full phase behaviour. It is believed that the mechanical parameters discussed above kc,k and J0, control the phase behaviour, where it is understood that these quantities may, in principle, depend on the overall surfactant (lipid) concentration, i.e. when the membranes are packed to such a density that they strongly interact. 

Fig. 2 A nitroxide scan on KcsA. (a) Linear representation of the putative transmembrane topology of KcsA and the nitroxide scan (linear scale with arrows), (b) Room temperature CW EPR spectra for two regions in TMl and TM2. Multiple nitroxide components are highlighted by red arrows in selected spectra, (c) Mobility and accessibility plots. Periodical pattern are visible. On the right, helical wheel representation showing the trends of the EPR parameters extracted from the spectra in a polar coordinate representation, (d) Example of dipolar broadening on position 108, and effect of underlabeling on the spectral shape. On the right the shortest distance...

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