Separation of double-stranded DNA fragments by capillary electrophoresis in interpenetrating networks of polyacrylamide and polyvinylpyrrolidone

Mixtures of two polymers with totally different chemical structures, polyac rylamide and at Stony Brook, polyvinylpyrrolidone (PVP) have been successfu lly used for double-stranded DNA Stony Brook, NY, USA separation. By polyme rization of acrylamide in a matrix of PVP solution, the incompatibility of these two polymers was suppressed. Laser light scattering (LLS) studies sho wed that highly entangled interpenetrating networks were formed in the solu tion. Further systematic investigation showed that double-stranded DNA sepa ration was very good in these interpenetrating networks. With a concentrati on combination of as low as 2% w/v PVP (weight-average molecular mass M-r = 1 x 10(6) g/mol) +1% w/v polyacrylamide (M-r = 4 x 10(5) g/mol), the 22 fr agments in pBR322/HaeIII DNA, including the doublet of 123/124 bp, have bee n successfully separated within 6.5 min. Under the same separation conditio ns, similar resolution could only be achieved by using polyacrylamide (M-r = 4 x 105 g/mol) with concentrations higher than 6% w/v and could not be ac hieved by using only PVP (M-r = 1 x 10(6) g/mol) with a concentration as hi gh as 15% w/v. It is noted that the interpenetrating network formed by 2% P VP and 1% polyacrylamide has a very low viscosity and can dynamically coat the inner wall of a fused-silica capillary. The separation reached an effic iency of more than 10(7) theoretical plate numbers/m and a reproducibility of less than 1% relative standard deviation of migration time in a total of seven runs. The interpenetrating network could stabilize polymer chain ent anglements. Consequently, the separation speed was increased while retainin g resolution.