Disclosed is a modified relaxin polypeptide comprising at least one non-naturally encoded amino acid, wherein: (a) the modified relaxin polypeptide comprises a relaxin A chain polypeptide and a relaxin B chain polypeptide, wherein said relaxin A chain polypeptide has a sequence at least 85% identical to SEQ ID NO: 4, and said relaxin B chain polypeptide has a sequence at least 85% identical to SEQ ID NO: 5 or SEQ ID NO: 6； and (b) the non-naturally encoded amino acid has the structure as defined herein wherein said non-naturally encoded amino acid is linked to a linker, polymer, or biologically active molecule.
