Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Separation of Large Circular DNA by Electrophoresis in Agarose Gels



Kenneth D. Cole, C M. Tellez


The electrophoresis of circular DNA, ranging in size from 4.4 kilobase pairs (kbp) to 220 kbp, was studied in agarose gels. Bacterial artificial chromosome (BAC) DNA was used as a source of large supercoiled and open circular (relaxed) forms. the open circles above approximately 50 kbp werre trapped at the sample wells of 1% agarose gels during electrophoresis at 3 V/cm. Field Inversion Gel Electrophoresis (FIGE) was used to relieve the trapping of the open circles in the gels. Using FIGE 930s forward pulse time), open circles with sizes of 115 kbp and 220 kbp required reverse pulse times of 3 s and 6 s, respectively, to free the circles from openended gel fibers. A minimum in the gel velocity of the open circles was measured at approximately 20 kbp the order was reversed. These results indicate that when the size of the open circles exceeded the average pore size of a gel and it was forced to span multiple pores, the open circles gained a mobility advange. Decreasing the ionic strength of the electrophoresis buffer significantly decreased the mobility of the smaller circles and slightly increased the mobility of the larger circles.
Biotechnology Progress
No. 1


agarose, DNA, electrophoresis, gel, plasmid, purification, separation, starch, trapping


Cole, K. and Tellez, C. (2002), Separation of Large Circular DNA by Electrophoresis in Agarose Gels, Biotechnology Progress (Accessed July 23, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created January 1, 2002, Updated February 17, 2017