Physical Society Colloquium

Interview for Faculty Position

Nanomechanics in Biology � From Single molecule experiments to multiple nano-mechanical biosensors

Martin Hegner

Instiute of Physics
University of Basel

Macroscopic experiments yield time and population averages of the individual characteristics of each molecule. At the level of the individual molecules, the picture is quite different: individual molecules are found in states far from the mean population, and their instantaneous dynamics are seemingly random. Whenever unusual states or the rapid, random motions of a molecule are important, the macroscopic picture fails, and a microscopic description becomes necessary. Single-molecule experiments provide access to some of the microscopic dynamics that are hidden in the macroscopic experiments.

We apply state-of-the-art combined optical tweezers (OT) which offer new opportunities to correlate nanoscale structural changes [monitored by fluorescence detection] upon a bio-mechanical transition induced by OT. Applications of combined measurements (fluorescence and force detection) will be presented. An introduction into current biological applications with a focus on nanomechanical measurements on a powerful molecular machine (VirE2-DNA) is shown. The machinery is responsible for the translocation of single-stranded DNA (ssDNA) across membranes of two cells.

Biosensing tools are currently undergoing a further stage of development. Future diagnostics will depend on fast, specific assays to allow personalized medical diagnostics. Increasing efforts in our group have therefore been put into the development of measurement- and functionalization schemes for cantilever-based sensors for the label-free detection of physical- and chemical phenomena of biological interactions. Cantilevers arrays offer an elegant approach where physiological ligand-receptor binding interactions occurring on the sensor generate nanomechanical signals like bending or a change in mass that is optically detected in-situ.

We report on new styles of combined measurements in the field of proteomics and genomics.