Separation of newly formed bone from older compact bone reveals clear compositional differences in bone matrix

► Newly formed bone's matrix composition is distinct from that of more mature bone. ► Select matrix proteins in younger versus older bone exhibit differences in post-translational modifications. ► These modifications involve proteolysis associated with mineralization or remodeling. ► These modifications also involve cross-linking into higher molecular sized forms. ► Newly formed bone rapidly transitions into mature bone involving temporal-spatial changes in matrix proteins.