Regensburg 2007 – scientific programme

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BP: Fachverband Biologische Physik

BP 11: Micro- and Nanofluidics

BP 11.5: Talk

Tuesday, March 27, 2007, 17:00–17:15, H43

Thermophoretic Biomolecule Analytics — •Stefan Duhr and Dieter Braun — Ludwig Maximilians Universität München, Center for Nanoscience (CeNS), Amalienstrasse 54, 80799 München

Molecules drift along temperature gradients, an effect called thermophoresis, Soret-effect or thermodiffusion. We present a recently developed microscopic theory [1] based on solvation entropy. Stated in simple terms, the Soret coefficient is given by the negative solvation entropy, divided by kT. The theory predicts the thermodiffusion of polystyrene beads and DNA without any free parameters. This description holds as long as particles are in local thermodynamic equilibrium, which is valid for small molecules at moderate temperature gradients. Based on this theory, slight changes of surface properties on the molecular level lead to profound changes in thermophoretic behavior. We show experimental results for fast molecule characterization by thermophoresis. Thermal gradients provide a good tool to differentiate between DNA of different length within a few seconds, but they also allow for detection of biomolecule interactions. Thermophoresis may proof a very effective technique for biotechnological applications.

Reference: [1] S.Duhr and D.Braun, Why molecules move along a temperature gradient, PNAS, in press