报告题目：From single molecules to whole cells: applications of force sensing
报告人：Dr. Philipp Rauch, JPK instruments AG, Berlin, Germany
报告摘要：Starting from the early 1970s, the discovery of light exerting forceson matter as the two interact, has laid the foundation for a whole classof new experimental approaches. The availability of stable, high powerlaser sources has made these approaches much easier to implement andoperate. In recent years, optical tweezers (OT) have generated remarkableinterest in research areas other than fundamental physics, includingbiochemistry, biology, and medicine. The ability to gain insight into the
mechanical processes and miniscule forces underlying protein folding,DNA-ligand interactions, cell adhesion, and cell mechanics opens a broadrange of new applications.
In single-molecule experiments, particles with well-defined opticalproperties (e.g. micrometer-sized polystyrene beads), are chemicallyattached to the molecule of interest. They serve as “handles” and
force sensors to manipulate the molecule and analyze its mechanicalresponse. A prominent application making use of the high speed andresolution in OT force detection is the investigation of DNA mechanics(Fig.1). Varying environmental conditions and the interaction withDNA-binding molecules mimic the different stages of DNA replication andcell division. Furthermore, the high resolution spatial tracking abilityof optical tweezers also delivers detailed insight in single moleculedynamics, e.g. the movement of individual motor proteins along acytoskeletal filament (Fig. 2). Complementing the measurementson a single- or few-molecule level, OT are also commonly used tocharacterise the mechanical behavior of very soft (biological orartificial) and complex visco-elastic matter on a micrometer scale. Thesemicro-rheology applications lead to a better understanding of cellular
mechanics and the properties of fluids and gels on microscopic dimensions.Many cellular processes including signaling, motility and growth areclosely related to the local mechanical conditions in- and outside of thecell. Figure 3 displays a typical measurement that determines the localrigidity and viscosity of a cell membrane, a crucial factor thatinfluences membrane activity.
Offering an easy-to-use setup that does not require deep backgroundknowledge, JPK enables researchers from all disciplines to benefit fromthe advantages of this fascinating technique. In combination withaccessories that perfectly integrate microfluidics or environmentalcontrol for live cell experiments, the NanoTracker™ optical tweezers covera wide range of applications including single-molecule force spectroscopy,the investigation of emulsions and colloidal suspensions, surface forces,
cell-ligand interactions as well as cell mechanics and cellular and fluidmicro-rheology. A short theoretical introduction and selected applicationsfrom different fields with exemplary results will be presented toillustrate the capability of optical tweezers systems in general and theversatility and usability of JPK’s NanoTracker™ platform in particular.