| A high Mr ( Mr 120 , 000 ) , disulphide bonded collagenous polypeptide was observed to co purify with the prox 1 ( 10 ) chain during isolation of cartilage collagens from culture medium of embryonic chick tibiotarsal chondrocytes . ^^^ This high Mr polypeptide was subsequently shown by two dimensions l SDS PAGE and peptide mapping to represent a dimer of the prox 1 ( 10 ) chain of type 10 collagen linked by disulphide bonding in the non collagenous domains . . ^^^ |