THEORY OF CAPILLARY ELECTROPHORETIC SEPARATIONS OF DNA-POLYMER COMPLEXES

Electrophoretic separation of DNA molecules normally requires the use of an anticonvection, sieving polymer matrix such as a gel or an entan gled polymer solution. Recently, it has been suggested that free-solut ion separation could be achieved in a capillary if an electrically neu tral, friction-generating molecule is attached to the DNA molecules be fore electrophoresis is carried out. The electrophoretic mobilities ar e then predicted to be very large and the resulting separation is expe cted to yield excellent resolution. The size-dependence of the electro phoretic mobility is attributed to longer DNA molecules pulling the ne utral molecule with a larger electric force, thus eluting earlier than shorter DNA molecules. In this article, we focus on the particular ca se where one attaches an uncharged, flexible polymer to the end of the DNA. Our self-consistent model takes into account the deformation and the hydrodynamic resistance of the polymer in the flow. We find vario us regimes, depending on the intensity of the electric field and the l ength of the polymer. The most favorable conditions for high-resolutio n separation of DNA are described.