Abstract: The present invention relates to: manipulation of the amino acid sequence of tropoelastin, particularly human tropoelastin, to modify its protease susceptibility; to tropoelastin derivatives having modified protease susceptibility; to peptidomimetic molecules which contain amino acid sequences which correspond to or incorporate the protease susceptible sequences of tropoelastin; and to uses of the tropoelastin derivatives and peptidomimetic molecules. The invention also relates to nucleic acid molecules and genetic constructs encoding the amino acid sequences of the derivatives and peptidomimetic molecules of the invention.