Anisotropic Raman scattering in collagen bundles.

Collagen is the main connective tissue protein of vertebrates and shows exceptional mechanical and optical properties. The alignment of collagen fibrils correlates to the function of a specific tissue and leads to optical anisotropy. The effect of the molecular alignment on Raman scattering, however, has barely been investigated. We found that the peak intensities of the C-C, C=O, and N-H vibrational modes, which are typical for the Raman bands of the protein backbone, change with the orientation of the collagen fibrils. These observations demonstrate that Raman spectra contain specific information regarding molecular and fiber alignment.