Issues linear macromolecule

The overall objective of this chapter is to review the fundamental issues involved in the transport of macromolecules in hydrophilic media made of synthetic or naturally occurring uncharged polymers with nanometer-scale pore structure when an electric field is applied. The physical and chemical properties and structural features of hydrophilic polymeric materials will be considered first. Although the emphasis will be on classical polymeric gels, discussion of polymeric solutions and nonclassical gels made of, for example, un-cross-linked macromolecular units such as linear polymers and micelles will also be considered in light of recent interest in these materials for a number of applications... 

Membrane filtration is an effective technique for the preconcentration of biological macromolecules like proteins and DNA. However, relatively low enrichment factors are obtained compared to 1.1.F, SPE, and TGF. Concentration enrichments with a factor of about 100 were shown for both proteins and DNA molecules by several groups. A problem that has to be taken into account is the probable adsorption of the macromolecules on the membrane surface. This could result in taUing in the injection channel and/or in a low recovery of the molecules. Another issue that has to be taken into account is the good probability that concentration increase is not a linear function of time, as observed by Khandurina et al. and Foote et al. ... 

So far, activation of mechanophores in the cyclic chain has not been reported. One important issue is the location of the mechanophore in the cyclic polymer. If only one mechanophore is incorporated into a ring chain (Fig. 18a), it is unlikely to experience the maximum hydrodynamic force (red dots) because the ring has no definitive midpoint in the flow field. Even if the ring chain breaks, the positimi of the mechanophore is unlikely to locate just at the midpoint of the linear product To improve the chance of activation, it is better to have multiple mechanophores incorporated into the cyclic chain, such as random, alternative, or block cyclic copolymers. For example, in Fig. 18b the mechanophores are randomly dispersed into a cyclic macromolecule to increase the activation probability. If the cyclic chain breaks, the mechanophores still have the chance to be located near the midpoint of the linear chain. The linear fragment then undergoes CST and activates the mechanophores. 

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