Molecular structure and physicochemical properties of pepsin-solubilized type II collagen from the chick sternal cartilage.

Recently, type II collagen (CII) was found to be effective clinically for treatment of rheumatoid arthritis (RA). However, the molecular properties of CII could be changed during the preparation process. In the present study, we isolated CII from chick sternal cartilage and studied the structural characteristics of purified CII. Pepsin-solubilized CII was purified from sternal cartilage of the chick using a combination of pepsin digestion, NaCl precipitation and DEAE-Sepharose CL 6B ion exchange chromatography. Then, the molecular structure and physicochemical properties of pepsin-solubilized CII were investigated. According to the electrophoretic patterns, the purified preparation consisted of a single band (α chain) and dimmers (β chains) with a subunit Mr of 110 kDa, were characterized to type II, and contained imino acid of 232 residues/1000 residues. The maximum transition temperature (Tmax) of the pepsin-solubilized CII measured by DSC was 45.60°C. Circular dichroism (CD) spectra analysis revealed that pepsin-solubilized CII retained more intermolecular crosslinks during the preparation process. Investigation results of atomic force microscope (AFM) indicated that the collagen fibrils from chick cartilage were about 146 nm in width and highly periodic with a banding pattern of -68.3 nm spacing. Analysis of physical properties indicated that pepsin-solubilized CII were highly solubilized in the pH range of 1-3.5 and the optimal NaCl concentration was 0.6 mol/L. Chick sternal cartilage can be used as an alternative CII source.