Spectroscopic studies of the effect of the metal ions on the structure of mucin

In this study the binding characteristics of mucin to calcium ion was examined by Fourier Transform Infrared (FT-IR), FT-Raman, Transmission Electron Microscope (TEM), and Dynamic Light Scattering (DLS) methods. The binding site of the interaction between mucin and calcium ions could be confirmed by FT-IR and FT-Raman techniques. When the concentration of Ca²⁺ is relatively low, Ca²⁺ prefers to coordinate with the carbohydrate moiety of mucins. When the concentration of Ca²⁺ is high, Ca²⁺ will also interact with the protein moiety of mucins. The morphology and the size of CaCl₂-mucin solution could be obtained by TEM and DLS methods, respectively. The hydrodynamic radius of CaCl₂-mucin mixture decreases compared with pure mucin solution, which may result from that Ca²⁺ induces a contraction or folding of mucin chains to form a more compact configuration. The activity of the cations in modifying the structure of mucin may be of great importance for the biological function in normal and disease states.