Capillary electrophoretic separation of dsDNA under nonuniform electric fields

Abstract

Improved sensitivity for the analysis of DNA by capillary electrophoresis has been achieved, based on simultaneous increases in optical path length and injection volume. To increase the optical path length, bubble cells with diameters ranging from 150 to 450 microm have been fabricated and tested. In terms of resolution and sensitivity, a bubble cell of 300 microm diameter is appropriate when using 75-microm capillaries. To allow greater injection volumes, we performed on-line concentration of DNA in the presence of electroosmotic flow (EOF) using 2.0% poly(ethylene oxide) (PEO). With a 300-microm bubble cell, a 170-fold improvement in the sensitivity for the 89-bp fragment has been accomplished when injecting about 0.33 microL DNA. In the presence of the bubble cell, the resolution for the large fragments improves while that for the small ones (<124 base pair) decreases. The effect of bubble cells was further investigated by conducting DNA separation in the absence of EOF, showing that improvements in resolution are mainly due to increased migration differences when DNA migrated at low electric field strengths in the bubble region. We have suggested that such an effect is more profound using shorter capillaries, leading to complete separation of phiX 174 RF DNA-Hae III digest in 2 min.

On‐line sample concentration techniques in capillary electrophoresis: Velocity gradient techniques and sample concentration techniques for biomolecules

“…Several on-line preconcentration methods have been developed by several researchers. Chang and co-workers [106][107][108] demonstrated the large-volume injection of a DNA sample by reducing the electrophoretic mobilities induced by a polymer solution containing poly(ethylene oxide) (PEO). In the presence of an EOF, after injecting a large volume of the ds DNA sample in a capillary filled with a buffer solution, the injection end of the capillary was immersed in a PEO solution.…”

Double-Stranded DNA Diffusion in Slitlike Nanochannels

“…The rate of this algebraic decay alone has never been tested (to our knowledge) to be able to dampen the disturbance enough to eliminate cooperative motion between polymer segments, although its orientational effects have been studied in the HI between colloids. [34][35][36][37] 3. Experimental Section 3.1.…”

A microfabricated CE chip for DNA pre‐concentration and separation utilizing a normally closed valve

“…For example, a nanoscale channel was integrated with microscale CE channels fabricated by standard photolithography and etching techniques for sample pre-concentration [32]. Significant stacking of DNA samples of 10 6 -10 8 -fold has been observed. With this approach, samples can be enriched and then separated and analyzed using micro-CE chips.…”

“…To improve the detection limit, many techniques have been developed, including the usage of an extended optical path length [6,7] and larger sample amounts for analysis [8]. The improvements in detection limit by using a longer path length can be also carried out in CE [9][10][11].…”