Structure-property relationships in major ampullate spider silk as deduced from polarized FTIR spectroscopy
Institut für Experimentelle Physik I, Universität Leipzig, Linnéstraße 5, 04103, Leipzig, Germany
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Accepted: 12 October 2007
Published online: 6 November 2007
Polarized Fourier Transform Infrared (FTIR) spectroscopy is employed to study structure-property relationships in major ampullate spider silk being exposed to an external mechanical strain. From the measured infrared dichroism of aminoacid-residue - specific bands the molecular order parameter, the frequency width at half-maximum (FWHM) and the spectral position of the absorption maximum are determined in dependence on the external strain. For the highly ordered alanine-rich β sheets a change in the vibrational potential is found for macroscopic strains as low as a few percent. It can be quantitatively described by a quantum-mechanical approach in which the mechanical strain is treated as a weak external perturbation. The immediate microscopic response to the external field proves that β -sheeted crystals are tightly interconnected by pre-stretched chains as suggested recently (Y. Liu et al., Nat. Mater. 4, 901 (2005)).
PACS: 87.15.-v Biomolecules: structure and physical properties – / 87.68.+z Biomaterials and biological interfaces – / 87.64.Je Infrared and Raman spectroscopy –
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag, 2007