EFFECT OF THE AGE OF NON-CROSS-LINKED POLYACRYLAMIDE ON THE SEPARATION OF DNA-SEQUENCING SAMPLES

Capillaries filled with non-cross-linked polyacrylamide and 7 M urea a re stable for at least 4 months when stored at room temperature and ex posed to the atmosphere. The stability of these capillaries when subje cted to four successive DNA sequencing runs at an electric field of 30 0 V/cm was studied. Capillaries used the day after polymerization show ed a dramatic increase in elution time with successive separations. Ca pillaries used at least 1 week after polymerization showed very reprod ucible elution times with successive separations. This effect was obse rved with capillaries where polymerization occurred in situ. Identical results were observed when polyacrylamide was formed in an external v essel and the polymerized material was pumped into the capillary. In a ll cases, there was a gradual loss in resolution with successive separ ations; this loss of resolution was independent of the length of time since polymerization. Separations may be made successfully up to at le ast 115 days after polymerization for fragments less than 300 bases in length.