Clay-enhanced DNA separation in low-molecular-weight poly(N,N-dimethylacrylamide) solution by capillary electrophoresis

The effect of the separation medium in capillary electrophoresis consisting of a low-molecular-mass poly(N,N-dimethylacrylamide) (PDMA) solution on th e DNA separation by adding a small amount of montmorillonite clay into the polymer matrix is presented. On the separation of the pBR322/HaeIII digest, both the resolution and the efficiency were increased by adding 2.5-5.0 x 10(-5) g/mL clay into the 5% w/v PDMA with a molecular mass of only 100 K. Moreover, there was no increase in the migration time of DNA fragments. Sim ilar results were observed by using a C-terminated pGEM-3Zf(+) sequencing D NA sample in a sequencing buffer. Experimental data also showed that the ad dition of clay increased the viscosity of the polymer solution. We attribut e this effect to the structural change of the polymer matrix caused by the exfoliated clay sheets, whereby the thin clay sheets function like a "dynam ic cross-linking plate" for the PDMA chains and effectively increase the ap parent molecular mass of PDMA.