Mechanical and structural properties of biological materials at the nano- and microscale

Mechanical forces are ubiquitous in biological systems. There are manifold examples of how biological entities as cells, bacteria and proteins are subjected to such forces and react to them. Cells can feel the stiffness of their surrounding tissue, transducing that signal in a process called mechanotransduction and then react to said signal. Cells exert well-defined forces onto each other through adhesion complexes while growing, tissue development and morphogenesis and malfunctions of these force transduction events are often connected to states of disease. Bacteria use the complex build-up of their cell wall to sustain the osmotic pressure of their environment, while still controlling their shape as needed for proper functioning of the organism. On the even smaller scale, adhesion proteins function as mechanical sensors, anchoring cells and bacteria to surfaces and working as the molecules that through changes in their conformation react to the applied forces. The aim of the present thesis is to investigate the mechanical properties of biological materials at the nano- and microscale. For this, thorough examinations using Atomic Force Microscopy (AFM) and Confocal Laser Scanning Microscopy (CLSM) have been performed on three different model systems: eukaryotic cells, bacteria and polyproteins. Through probing the properties of such systems using techniques of force spectroscopy, the mechanical properties of the cellular system were determined, while using single molecule force spectroscopy (SMFS) the mechanical unfolding kinetics and energetics of single proteins were investigated. In addition, CLSM permitted to elucidate the role and dynamics of cytoskeletal components and focal adhesions. Overall, this thesis provides a framework on measuring the mechanics of biological systems at the nano- and microscale. (author)