DNA CONFORMATIONAL DYNAMICS IN POLYMER-SOLUTIONS ABOVE AND BELOW THE ENTANGLEMENT LIMIT

Video microscopy of nucleic acids (DNA) undergoing electrophoresis in hydroxyethyl cellulose (HEC) sieving buffers demonstrates previously u nobserved shape-changing interactions between DNA and HEC molecules. W e provide the first visual demonstration of entanglement between DNA a nd one or several discrete HEC molecules, which has been postulated to occur in ultradilute polymer solutions. Typically, nucleic acids appe ar to become entangled with HEC at a single region only, in both dilut e and fully entangled HEC solutions. Fluctuations of the center of mas s velocity of a DNA molecule and its correlation with conformation are revealed from analyses of the image data. These observations account for the success of recently reported rapid, high-resolution dc and pul sed-field capillary electrophoretic separations of nucleic acids in ul tradilute hydroxyethyl cellulose solutions and hydroxyethyl cellulose/ poly(ethylene oxide) solutions.