Reptation stretching regime

As we can see from Eqs. (32), Xg in the reptation-without-stretching regime N0 <1, while XE NB-Hn NB ) for the very large "plateau molecules. This important change in behaviour indicates that the field-induced disengagement time Xg is less molecular-size dependent but more field dependent for larger molecules. 

Figure 2 Schematic view of DNA migration regimes (A) Ogston sieving (B) biased reptation and (C) reptation with permanent stretching. Rg - radius of hydrodynamic equivaient sphere of DNA coii S - average mesh size.

This regime is the so-called reptation-with-stretching. A mobihty plateau is observed for large DNA (above the critical length, N ) in the case of high electric field and resolution approaching 0. Fig. 2 shows the dependence of DNA mobihty on its size. 

The BRM does reproduce both the reptation-without-stretching (p l/L) and reptation-without-stretching (p-Pp) regimes observed experimentally and described qualitatively in section IV.1. The existence of a minimum mobility for a finite value of is a surprising prediction of the BRM. 

I. For shear rates lower then 1/tj, where is the reptation or disengagement time, no noticeable influence of the flow is observed that is, the crystallization takes place as for quiescent conditions. For this regime the related Weissenberg numbers, defined as Wig = (related to molecular orientation) and WU = Tr, where Xr is the Rouse time (related to molecular stretch), are both smaller than 1, that is, Wio < 1, Wi s < 1. 

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