Characterization of the complex of human-like collagen with calcium.

The calcium complex of human-like collagen (HLC) was generated in aqueous solution, purified by dialysis or ultrafiltration, and isolated by freeze-drying. Evidence for interactions between HLC and calcium(II) was obtained through measurements of the complex's fluorescence and UV-visible spectra, the interpretation of its Fourier transform infrared spectroscopy and circular dichroism spectra, thermogravimetric (TG) analysis, and differential scanning calorimetry (DSC). The HLC-Ca complex is considered a new chemical compound in which HLC retains its helical structure and the calcium ion is linked to the protein via C=O and N-H groups. Additionally, TG and DSC measurements indicate that the HLC-Ca complex is thermodynamically more stable than free HLC. The results obtained provide important evidence for the further study of the interactions of HLC with Ca(II).