Dynamics of T2 DNA during electrophoresis in entangled and ultradilute hydroxyethyl cellulose solutions

Microscopy of DNA in Dilute Polymer Solutions

“…At 50 V/cm in the 0.09% HEC 438K solution with T4 DNA, the average maximum extension of one arm of the U‐shape is 9.9 μm ( n = 14), which corresponds to an average value of R l = 2.97 μm, while at 33 V/cm in a 0.01% HEC 438K solution, the average maximum extension of one arm of the U‐shape is 7.1 μm ( n = 15), which corresponds to an average value of R l = 2.14 μm. These values are qualitatively similar to those found by Hammond et al, who showed apparent lengths at greatest extension of 13.9 μm for T2 DNA in a 0.01% HEC 438K solution in 55−60% sucrose at 72 V/cm (11). DNA extensions were less in the lower molecular mass polymer solution: at 33 V/cm in a 1.5% solution of HEC 27K, the average maximum extension of one arm of the U‐shape is 5.8 μm ( n = 8), corresponding to an average value of R l = 1.81 μm.…”

“…The collision process does not result in a stationary DNA molecule, as even the apex of a U‐shaped extension continues to travel in the electric field. The center‐of‐mass velocity decreases during both types of polymer collisions, similar to the velocity fluctuations shown by Hammond et al (11). It is likely that the polymer obstacles encountered by the DNA are single polymer molecules, but it is also possible that the DNA will also collide with an entangled glob of multiple polymer molecules.…”

“…The DNA was also found to become hooked around obstacles, forming U‐shapes which then slide around the obstacle as the DNA resumes its forward motion. The Morris group and Carlsson et al have studied DNA electrophoresing through polymer solutions both above and below the entanglement threshold (9−11), using fluorescence microscopy. These studies show that the dynamics of DNA migrating through polymer solutions shares some characteristics with that of DNA migrating through gels.…”

Band broadening during dc and field inversion capillary electrophoresis of λ DNA in dilute hydroxyethylcellulose solutions

“…The gel electrophoresis model assumes a non-deformable ion migrating through an array of stationary obstacles. In the DNA case we have shown that there is a distribution of DNA-obstacle disentanglement times, 15 but in dilute or semi-dilute solution electrophoresis entangled DNA is not stationary. Instead, the obstacles move along with the DNA.…”

“…A decade of video microscopy in both gels and polymer solutions shows that ds-DNA undergoes a cycle of collision with the matrix, extension, disentanglement from the matrix and collapse towards a random coil. [11][12][13][14][15] The extension-collapse cycle is observed in every matrix from gels [11][12][13] to dilute polymer solutions, 14,15 but it is not included in the Weiss model.…”