| Regional Biophysics Meeting 2005, March 16-20, Zreče, Slovenia | [NanoBioTech] |
In recent years it became possible to grab, hold and manipulate individual molecules and thereby explore their elasticity, intramolecular interactions and force-driven structural transitions. We use optical tweezers and scanning force microscopy combined with recombinant techniques to investigate various biomolecular systems. Titin is a giant filamentous protein responsible for maintaining the structural integrity of the muscle sarcomere. It is composed of ~300 globular, beta-barrel domains interspersed with unique sequences. By stretching individual molecules we revealed that the molecule behaves as an entropic, wormlike chain in which domain unfolding occurs during stretch and refolding during relaxation. Differences in the unfolding and refolding kinetics result in a force hysteresis. By manipulating recombinant fragments of titin the mechanical stability along titin is mapped. Desmin is the muscle-specific intermediate filament protein that is thought to play an important role in trasmitting intracellular forces. The mechanical response of desmin filaments is characterized by non-linear elasticity with superimposed force transitions that are related to the unfolding of alpha-helical domains within the protofilament. The results also indicate that the longitudinal stability of the desmin filaments exceeds its transverse stability. Amyloid beta-fibrils are formed by the cooperative association of the 40 to 42-amino-acid-long amyloid peptide. The structure of amyloid fibrils is difficult to explore with conventional methods. In mechanically manipulated amyloid fibrils force plateaus and staircases appear, which are attributed to the unzipping of protofibrils from the surface of the fibril. The force transitions are reversible during mechanical relaxation, suggesting that the protofibrils rapidly re-integrate into the fibril. In sum, nanobiotechnology methods provide a unique insight into the mechanics, structure and dynamics of biological molecules.
Email: miklos.kellermayer.jr@aok.pte.hu
Address: Department of Biophysics, University of Pécs, Faculty of Medicine, Szigeti ut 12., Pécs, H-7624 Hungary