Separation of β22 dimer from bovine bone collagen

The precise role of the α 2 -chain in collagen type I is of considerable scientific interest. Our recent studies demonstrated that the most noticeable difference between type I collagens, which were obtained from bovine hard tissues (bone, dentine) and soft tissues (tendon, skin), was presented in the position of β chain dimers using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. The additional band observed both in the bone and dentine collagen was putatively identified as β 22 dimer (made of by an intermolecular cross-linking between two α 2 -chains). Further investigations carried out on bovine bone and skin collagen, corresponding to hard tissue and soft tissue collagen respectively, confirmed this hypothesis. Successful separation of individual β 22 dimer from bone collagen was achieved. The procedure involves molecular-sieve chromatography on a Sephacryl S-400 column followed by differential acetone precipitation. Identification was done by the widely used methods, such as SDS-PAGE and cyanogen bromide (CNBr)-cleaved peptide analysis. It was proposed that the dimer and consequently α 2 -chains may play important roles in the morphological and biological differences between hard and soft tissues.