Dresden 2003 – wissenschaftliches Programm

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SYMM: Bio- and macromolecules at work - from motor proteins to soft actuators

SYMM 1: Symposium Bio- and macromolecules at work - from motor proteins to soft actuators

SYMM 1.1: Hauptvortrag

Mittwoch, 26. März 2003, 14:30–15:00, ZEU/160

Mechanical properties of single motor proteins - linking structure and function — •Heinrich Hörber — Department of Physiology, School of Medicine, 540 E. Canfield Av, Detroit MI48201

In the context of evolution, nature has developed many elegant ”nano-technological” concepts. In the cells of our body innumerable examples of multi-functional, self-organizing and self-reproducing molecular structures are found. All cellular functions are performed by groups of highly specialized molecules carrying out exact programs. These components possess an extremely high efficiency level and their functions are regulated stably and precisely, both by networking with other functional groups as well as by reacting to changing environmental conditions. Thus biologists talk about proteins like machines for good reason: proteins function like machines with specific tasks equipped with built-in programming and often with a chemical on/off switch. It is possible to use and even change the functions of proteins for technological applications. For certain molecular structures mechanical properties are the most relevant features for their function. Three-dimensional analysis of thermal position fluctuations can reveal mechanical properties, for instance of molecular motor proteins like Kinesins or Myosins by recording the fluctuations of a nanoscale bead tethered by a single motor molecule to its molecular track. Such measurements became possible by a novel three-dimensional scanning probe microscope we developed. The Photonic Force Microscope (PFM) allows to determine the position of a bead with nanometer 3-D spatial and microsecond temporal resolution. The position fluctuations can be transformed into three-dimensional energy profiles using the Boltzmann equation. Energy profiles and their changes are accessible with a resolution of one tenth of the thermal energy. From such profiles, force versus extension and in this way stiffness at the thermal excitation level can be determined along arbitrary paths in three dimensions. These measurements complement AFM studies of protein unfolding revealing at higher forces information on internal forces determining the 3-D structure of macromolecules. With such investigations Scanning or Local Probe Techniques developed into important new tools to understand the relation between molecular structure and function at the single molecule level.