Separation and manipulation of biomolecules

Separation and manipulation of biomolecules

DNA separation at liquid-liquid interfaces

The size separation of DNA molecules remains a highly relevant task in a number of different applications, for example Next Generation Sequencing. We have developed a novel method of DNA separation relying on the electrophoretic accumulation of DNA strands at a liquid-liquid interface, followed by their detachment in an electric field. It turns out that the detachment process is size specific, with the smaller DNA strands detaching at lower field strength values than the larger ones. That way it is possible to separate molecules in the size range below 1000 base pairs.

The figure below shows λ-DNA molecules that have been accumulated at an interface between two immiscible polymer solutions. The blow up indicates that larger molecules such as λ-DNA become stretched before detaching from the interface.

The second figure displays the process of DNA size separation. At the left, a relatively weak electric field is applied normal to the liquid-liquid interface, resulting in the accumulation of a mixture of different molecules. When the electric field strength is increased, waves corresponding to different size fractions detach from the interface (right).

The potential of this new method of DNA size separation was recently recognized by the Science4Life Initiative, see

Key publications

T. Hahn and S. Hardt, Concentration and size-separation of DNA samples at liquid-liquid interfaces, Anal. Chem. 83 (2011), 5476–5479.

T. Hahn and S. Hardt, Size-dependent detachment of DNA molecules from liquid-liquid interfaces, Soft Matter 7 (2011), 6320–6326.