Nonlinear electrophoretic focusing of DNA macromolecules

A new approach to focusing DNA molecules in a nonuniform electric field based on nonlinear mobility (L. L. Frumin, S. E. Peltek, S. Bukshpan, V. V. Chasovskikh and G. V. Zilberstein, PhysChemComm, 2000, 11) is proposed. The focusing is carried out in an alternating nonuniform electric field, created by using a wedge gel with hyperbolic boundaries. Methods of the theory of analytical functions were used to demonstrate that the fractions separated electrophoretically in such a wedge retain their rectilinear shape. Solutions for the focusing points for the case of mere velocity cubic nonlinearity were obtained as well as for the square velocity nonlinearity, suggested in a number of modern approaches. Gel electrophoresis experiments supported the possibility of a pronounced nonlinear focusing of DNA molecules. This nonlinear separation technique presents encouraging prospects for preparative isolation of long DNA fragments and development of new separation methods for bacterial fingerprinting.