First-principles calculations of Raman vibrational modes in the fingerprint region for connective tissue

Vibrational spectroscopy has been widely employed to unravel physical-chemical properties of biological systems. Due to its high sensitivity to monitor real time "in situ" changes, Raman spectroscopy has been successfully employed, e.g., in biomedicine, metabolomics, and biomedical engineering. The grounds of interpretation of Raman spectra in these cases is the isolated macromolecules constituent vibrational assignment. Due to this, probe the anharmonic interactions or the mutual interactions among specific moieties/side chains to name but a few is a challenge. We present a complete vibrational modes calculation for connective tissue in the fingerprint region ($800-1800$ cm$^{-1}$) using first-principles Density Functional Theory. Our results indicated that important spectral features correlated to molecular characteristics have been ignored within the usual tissue spectral bands assignments. In particular, we found that the presence of confined water is the main responsible for the observed spectral complexity. Our calculations accounted for the inherent complexity of the spectral features in this region and useful spectral markers for biological processes were unambiguously identified.