A TRANSIENT ENTANGLEMENT COUPLING MECHANISM FOR DNA SEPARATION BY CAPILLARY ELECTROPHORESIS IN ULTRADILUTE POLYMER-SOLUTIONS

Using capillary electrophoresis, large DNA molecules (2.0-23.1 kbp) ma y be rapidly separated in ultradilute polymer solutions (< 0.002% w/w) under a high-voltage, steady field (265 V/cm). At this polymer concen tration, the separation mechanism appears to be significantly differen t from that postulated to occur in crosslinked gels. Based on experime ntal results obtained with DNA restriction fragments and with negative ly charged latex microspheres, we conclude that the Ogston and reptati on models typically used to describe gel electrophoresis are not appro priate for DNA separations in such dilute polymer solutions. Electroph oresis experiments employing solutions of both small and large hydroxy ethyl cellulose polymers highlight the importance of polymer length an d concentration for the optimum resolution of DNA fragments varying in size from 72 bp to 23.1 kbp. A transient entanglement coupling mechan ism for DNA separation in dilute polymer solutions is developed, which suggests that there is no. a priori upper size limit to DNA that can be separated by capillary electrophoresis in a constant field.