Conventional reptation

It is not difficult to reproduce an expression for the correlation function Ma(t) and estimate times of relaxation due to the conventional reptation-tube model (see Section 3.5). Indeed, an equation for correlation function follows equation (3.48) and has the form... 

The results of estimation of coefficient of self-diffusion due to simulation for macromolecules with different lengths are shown in Fig. 12. The introduction of local anisotropy practically does not affect the coefficient of diffusion below the transition point M, the position of which depends on the coefficient of local anisotropy. For strongly entangled systems (M > M ), the value of the index —2 in the reptation law is connected only with the fact of confinement of macromolecule, and does not depend on the value of the coefficient of local anisotropy. At the particular value ae = 0.3, the simulation reproduces the results of the conventional reptation-tube model (see equation (5.21)) and corresponds to the typical empirical situation (M = 10Me). 

The first factor (xqA ) in Eq.(l8) describes the conventional reptation, while 1 describes all barrier effects. We then get explicit formulas for te by insertion of Ea. (17) for. For instance, with a saturated layer, we expect ze ... 

M. Rubinstein Yes, it does. In fact, this is one of the main features of the repton model that it includes this type of fluctuation of tube length neglected in the conventional reptation model. 

Two-Dimensional Pulsed Field Electrophoresis Theoretical Background. Applying the polymer reptation model to conventional DNA electrophoresis is proving to be quite successful, especially in the case of field strength dependent electrophoretic mobilities. 

Conventional CE in continuous electric fields cannot separate DNAs above 40 kb, due to reptation and loss of resolution. One has to resort to pulsed-field gel electrophoresis. This technique makes use of periodically varied direction and strength of an electric field (the net field direction is forward). The DNA molecules not only migrate in the direction of the field but also stretch out lengthwise. The time required for relaxation is directly proportional to the molecule length. Longer molecules relax less than shorter ones when the current is changed. DNA molecules are forced to reorient and are separated according to their sizes. 

I lie experimental results concerning dynamic light scattering in polymer solutions indicate the existence of two diffusion modes of a maeromolecule. The first mode is concerned with the conventional self-diffusion coefficient of the polymer. To the second one is as cribed the reptation motion of the maeromolecule in an imaginary pipe of enlanglemonl points formed from other macromolecules. 

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