Talk Krishnan 07

==Electrostatic stretching of DNA and trapping of charged colloids in a nanoslit (20. Nov. 2007)==

Madhavi Krishnan, PhD Biophysics Group Biotechnologisches Zentrum Technische Universität Dresden

I will present results on the stretching of DNA molecules and trapping of charged colloidal particles confined in solution to two dimensions in negatively charged nanoslits. The phenomenon arises from the combined effects of confinement and electrostatics in nanoslits. DNA molecules in slit-shaped silicon dioxide-glass channels, a few microns wide and 50 to 100 nm deep, spontaneously shed configurational entropy and assume axially extended configurations at the lateral sidewalls of the slit. The situation resembles that of extension of a physically confined polymer chain in a nanochannel, with the important exception that the nanochannel confines the DNA molecule in two of three spatial dimensions, while the nanoslit involves actual physical confinement in only one spatial dimension; confinement in the second spatial dimension is gratuitous, and appears to be electrostatically mediated. Not only are these phenomena interesting from a fundamental standpoint, but the almost complete stretching of DNA observed in our experiments could have far-reaching technological implications, presenting us with a new class of microdevices for genomic analyses.