Discriminative processing

The main challenge in designing clinically useful sensors is definitely the production of the electroactive element, i.e., the sensor membrane. The membrane is the place where the chemical recognition and discrimination processes occur. The membrane dictates, overwhelmingly, the quality of signal and durability of the sensor. Only a restricted number of membranes can be and are used in routine electrolyte and blood gas measurements ... 

The survey of the literature that we have carried out demonstrates that chiral discrimination is a widespread phenomenon whose incidence is rapidly growing. Although the energetic differences are small in the chiral discrimination processes... 

The effect of surface polarity is even more important in separations where two or more simultaneous interactions must occur in order to achieve the desired selectivity. This is particularly true in chiral separations. Since aqueous buffer systems are almost universally used as CEC mobile phases, enantioseparations are often run under re-versed-phase conditions as opposed to the normal-phase mode typically used in chiral HPLC. Therefore, non-specific hydrophobic interactions would be highly detrimental to the discrimination process that involves subtle differences between the enantiomers. 

The chiral discrimination process studied for quinine and binaphthol 29 (R = i-Pr) by using 1H NMR spectroscopy led to the conclusion that the primary forces responsible for the enantiodiscrimination are the hydrogen bonds and steric interactions [57, 58], Optimization studies on quinine for the enantioseparation of carbinol 28 (Ar = 9-anthryl, R = CF3) on quinine CSP 25 carried out by Nesterenko et al. showed that under normal conditions the best selectivity (a 1.53) could be... 

Yamamoto N, Hashimoto A, Takemoto Y, Okuyama H, Nomura M, Kitjaima R, et al. Effect of the dietary alpha-Unolenate/linoleate balance on lipid compositions and learning ability of rats. IL Discrimination process, extinction process, and glycolipid composition. J Lipid Res 1988 29 1013-1021. 

Newborn children from mothers who ate oontaminated fish were more likely to exhibit hypoactive reflexes, more motor immaturity, poorer lability of states, and greater amount of startle. Testing at 4 years of age found that prenatal exposure was associated with poorer performance on the Verbal and the Memory scales of the McCarthy Scales of Children s Abilities, as well as less efficient visual discrimination processing and more errors in short-term memory scanning. Evaluation of the children at 11 years of age showed that prenatal exposure was significantly associated with lower full-scale and verbal IQ scores and poorer reading word comprehension. 

Several reasons are invoked to explain the low selectivities. First, if we compare the small energy differences involved in chiral discrimination processes and the high energy content of excited states or of reactive intermediates, stereoselective processes do not seem likely. Second, the lifetimes of these intermediates might be too short to allow optimal interactions with a chiral inductor. Finally, one might wonder if the interactions that formed in the examples studied to date were strong enough to induce important selectivities. Recent reports indicate that asymmetric photoreactions must now be reconsidered [3],... 

The diversity around us, including the biological world (life), emerges from and depends on the ability to distinguish and exploit alternatives (selectivity). This discriminative process can rest on the energetic differences in thermodynamically definable and thus time-invariant states representing, however, in many cases, a... 

The temperature is the determining factor for the discrimination process of (/ )-(-) and (5)-(- -)-sotalol by immobilized cellobiohydrolase 1 (CBH 1), as it influences, not only the extent, but also the sign of enantioselectivity. An inversion of the enantiomeric elution order was also induced by changes in the organic modifier added to the buffer solution. 

The residual properties of oviposition-deterring pheromones are of particular importance to the host discrimination process. In cases where deterrent components from occupied resources may be emitted until completion of larval development, such as pheromonal release by larvae of Ephestia, Plodia and Heliothis, host discrimination mediated by pheromone may remain at a high level. However, in cases where deterrent components have only moderate residual activity under dry conditions or are water-soluble, both of which characterize tephritid pheromones, host discrimination mediated by pheromone may break down well before the completion of larval development. Here, one might suspect selection would favor female detection of larvae, or their effects. This does in fact seem to be the case in R. complete (Cirio, 1972) and R. pomonella (Averill and Prokopy, unpublished data), but further research is needed to explore this aspect more fully. 

Simkiss, K. 1981a. Cellular discrimination processes in metal accumulating cells. 7. Exp. Biol. 94 317-327. 

Efficient enantioface selection during insertion is caused by monosubstitution at the C4-carbon atom of the dihydroxazole ring (R or = H). The enantioface prevailingly inserted (and, therefore, the absolute configuration of the asymmetric carbon atoms in the polymeric chain) depends on the geometry of the C4-carbon atom. The presence of an R substituent is not essential for the discrimination process. 

Fig. 13.1 Postulated chirality-discrimination process to induce nonlinear effects.

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