Berlin 2008 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

CPP: Fachverband Chemische Physik und Polymerphysik

CPP 29: Polymerphysics I

CPP 29.12: Talk

Thursday, February 28, 2008, 12:30–12:45, C 130

Structural levels of organization in spider silk as studied by time-resolved polarized Rheo-FTIR spectroscopy — •Periklis Papadopoulos, Jan Sölter, Immanuel Weidner, and Friedrich Kremer — Universität Leipzig, Germany

The employment of polarized FTIR spectroscopy in combination with mechanical measurements is unique in unraveling the effects of external fields on the different moieties of spider silk under both equilibrium and non-equilibrium conditions. This allows us to construct quantitative structural models for the major (dragline) and minor ampullate spider silk and explain the differences between their respective mechanical properties. Both silks are semi-crystalline with β-sheeted crystals interconnected by pre-strained amorphous chains. The frequency shift of several absorption bands, in combination with a simple quantum mechanical model, allows tracing the microscopic force on the crystals and its distribution[1]. Thus, the structural model delivers the experimentally observed stress-strain dependence for both major and minor ampullate silk[2]. The former has a significantly higher degree of pre-strain, explaining its higher modulus, the lower extensibility and the effect of supercontraction, whereas the latter exhibits some degree of strain-induced crystallization. The very high toughness in both cases is attributed to the breaking of hydrogen bonds in the crystals.

[1] Papadopoulos, P.; Sölter, J. and Kremer, F. Eur. Phys. J. E: Soft Matter (2007) in press

[2] Papadopoulos, P.; Sölter, J. and Kremer, F. Biophys. J. (2007) submitted