A peptide-containing compound that comprises a peptide component that comprises or consists of: (a) the amino acid sequence: X-Pro-Y-Z (SEQ ID No: 5), wherein: X represents a chain of 1 to 2 amino acid residues each independently selected from the group consisting of Ala and Lys; Y is selected from the group consisting of Ser and pSer; and Z represents a chain of 1 to 7 amino acid residues each independently selected from the group consisting of Tyr, pTyr, 3Hyp or 4Hyp, Thr, pThr, DOPA and Lys; (b) the amino acid sequence: G 1 -Lys-Pro-G 2 -T-Hyp-G 3 -Lys (SEQ ID No: 7), wherein G 1 is absent or represents Ala; G 2 is selected from the group consisting of Ser and pSer; T is selected from the group consisting of DOPA, Tyr and pTyr; Hyp is selected from the group consisting of 3Hyp and 4Hyp; and G 3 represents a chain of 1 to 3, or 1 to 4, amino acid residues each independently selected from the group consisting of Tyr, pTyr, 3Hyp, 4Hyp, Thr, pThr and DOPA; (c) the amino acid sequence: Lys-Pro-G 2 -T-Hyp-G 3 -Lys (SEQ ID No: 8), wherein G 2, T, Hyp and G 3 are as defined above; or (d) the amino acid sequence: Ala-Lys-Pro-G 2 -T-Hyp-Hyp-Thr-G 4 -Lys (SEQ ID No: 9), wherein G 4 is selected from the group consisting of Tyr, pTyr, 3Hyp, 4Hyp, Thr, pThr and DOPA, and G 2, T, and Hyp are as defined above; and at least one of the Lys residues, and/or, where present, the Ala residue, of the peptide component is covalently bonded to one or more compounds of the formula I, wherein: R 1 is selected from the group consisting of -C(CH 3) 2 OH, -COCH 3, -C(CH 3)=CH 2 and -C(CH 3) 2 H; and n is 0, 1 or 2, as well as regioisomers, stereoisomers, and pharmaceutically- or cosmetically-acceptable salts of said peptide-containing compound. (a) the amino acid sequence: X-Pro-Y-Z (SEQ ID No: 5), wherein: X represents a chain of 1 to 2 amino acid residues each independently selected from the group consisting of Ala and Lys; Y is selected from the group consisting of Ser and pSer; and Z represents a chain of 1 to 7 amino acid residues each independently selected from the group consisting of Tyr, pTyr, 3Hyp or 4Hyp, Thr, pThr, DOPA and Lys; X represents a chain of 1 to 2 amino acid residues each independently selected from the group consisting of Ala and Lys; Y is selected from the group consisting of Ser and pSer; and Z represents a chain of 1 to 7 amino acid residues each independently selected from the group consisting of Tyr, pTyr, 3Hyp or 4Hyp, Thr, pThr, DOPA and Lys; (b) the amino acid sequence: G 1 -Lys-Pro-G 2 -T-Hyp-G 3 -Lys (SEQ ID No: 7), wherein G 1 is absent or represents Ala; G 2 is selected from the group consisting of Ser and pSer; T is selected from the group consisting of DOPA, Tyr and pTyr; Hyp is selected from the group consisting of 3Hyp and 4Hyp; and G 3 represents a chain of 1 to 3, or 1 to 4, amino acid residues each independently selected from the group consisting of Tyr, pTyr, 3Hyp, 4Hyp, Thr, pThr and DOPA; G 1 is absent or represents Ala; G 2 is selected from the group consisting of Ser and pSer; T is selected from the group consisting of DOPA, Tyr and pTyr; Hyp is selected from the group consisting of 3Hyp and 4Hyp; and G 3 represents a chain of 1 to 3, or 1 to 4, amino acid residues each independently selected from the group consisting of Tyr, pTyr, 3Hyp, 4Hyp, Thr, pThr and DOPA; (c) the amino acid sequence: Lys-Pro-G 2 -T-Hyp-G 3 -Lys (SEQ ID No: 8), wherein G 2, T, Hyp and G 3 are as defined above; or (d) the amino acid sequence: Ala-Lys-Pro-G 2 -T-Hyp-Hyp-Thr-G 4 -Lys (SEQ ID No: 9), wherein G 4 is selected from the group consisting of Tyr, pTyr, 3Hyp, 4Hyp, Thr, pThr and DOPA, and G 2, T, and Hyp are as defined above; and at least one of the Lys residues, and/or, where present, the Ala residue, of the peptide component is covalently bonded to one or more compounds of the formula I, wherein: R 1 is selected from the group consisting of -C(CH 3) 2 OH, -COCH 3, -C(CH 3)=CH 2 and -C(CH 3) 2 H; and n is 0, 1 or 2, as well as regioisomers, stereoisomers, and pharmaceutically- or cosmetically-acceptable salts of said peptide-containing compound. wherein G 4 is selected from the group consisting of Tyr, pTyr, 3Hyp, 4Hyp, Thr, pThr and DOPA, and G 2, T, and Hyp are as defined above; and at least one of the Lys residues, and/or, where present, the Ala residue, of the peptide component is covalently bonded to one or more compounds of the formula I, R 1 is selected from the group consisting of -C(CH 3) 2 OH, -COCH 3, -C(CH 3)=CH 2 and -C(CH 3) 2 H; and n is 0, 1 or 2, as well as regioisomers, stereoisomers, and pharmaceutically- or cosmetically-acceptable salts of said peptide-containing compound.