Biopolymers and cell. 2008; 24 (2): 105 - 111

Reversibility of DNA loops exit during single cell gel electrophoresis

K. S. Afanasieva, T. A. Shuvalova, M. O. Zazhytska, A. V. Sivolob

The kinetics of DNA exit during single cell gel electrophoresis (comet assay) of human lymphocytes has been investigated. The electrophoresis was performed at neutral pH in the absence/presence of different ethidium bromide concentrations. The dependence demonstrated of DNA exit efficiency on ethidium bromide concentration points out that the comet tail consists of DNA loop domains extended by the electric field. The loop exit is facilitated significantly by relaxed DNA torsional constraint. However, the disappearance of comets was observed after switching off the electric field at the condition of some constraint in the extended loops. Several possibilities of applications of discovered effects to improve the comet assay were discussed.

Keywords: comet assay, loop domains, ethidium bromide, DNA torsional constraint.