Duplex concentration-independent

Notice the particular features of this kind of ohgonucleotide the hexameric sequence is said to be self-complementary, since two identical molecules can form a duplex via Watson and Crick bases. It may also be noted from Figure 7.5 that two parallel pathways compete for the formation of the template T, namely the template-dependent, autocatalytic pathway, and the template-independent, non-autocatalytic one. This competition is the reason why the initial rate of the autocatalytic synthesis was found to be proportional to the square root of the template concentration -something that von Kiedrowski and colleagues called the square-root law of autocatalysis. As Burmeister (1998) put it ... 

At the limiting current the surface eoncentration of reaction products reaches saturation and a salt film precipitates. The potential drop at the electrode is then determined essentially by the conduction properties of the surface film. For the case of iron dissolution in concentrated chloride solution the salt film was found to have a duplex structure, consisting of an inner eompact and an outer porous layer [21]. The thickness of the compact layer, where most of the potential drop oceurs, increases linearly with applied potential. On the other hand, the rate of dissolution of the salt layer is governed by mass transport and therefore is independent of potential. Thus the anodic current remains constant even if the potential difference aeross the salt film increases. Eventually, at sufficiently high potentials, other reaction phenomena may occur that lead to a renewed current rise, in a similar way as discussed in Section 4.3.1 for the limiting current of copper deposition. 

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