Patent ID: 7049398

Claim:
A manufactured peptide and pharmaceutically acceptable salts thereof comprising a metal ion-binding domain comprising two or more contiguous amino acids and a biological-function domain specific for one or more melanocortin receptors and a metal ion selected from the group consisting of rhenium and technetium complexed to the metal ion-binding domain, wherein at least a portion of said biological-function domain is co-extensive with at least a portion of the metal ion-binding domain, and wherein said biological-function domain is conformationally constrained upon complexing the metal ion-binding domain with a metal ion, and wherein the peptide or salt thereof is substantially more specific for one or more melanocortin receptors when the metal ion-binding domain is complexed with a metal ion than is the peptide or salt thereof when the metal ion-binding domain is not complexed with a metal ion, wherein the peptide is of the formulas: R 1 -Lll-Aaa-Bbb-Ccc-R 2 , R 1 -Bbb-Aaa-Ccc-R 2 , R 1 -Ddd-Bbb-Aaa-R 3 , R 4 -Eee-Bbb-Ccc-R 2 , R 1 -Hhh-Aaa-Bbb-Ccc-R 5 , or R 1 -Iii-Iii-Ccc-Jjj-Kkk-R 2 , wherein R 1 comprises a functionality that potentiates the intrinsic activity of the remainder of the peptide, including but not limited to providing an auxiliary or secondary receptor contact; Aaa is an L- or D-configuration cationic amino acid with a positively charged side chain; Bbb is an L- or D-configuration amino acid with an aromatic side chain; Ccc is an amino acid that provides both a nitrogen atom (N), from the alpha amino group, and a sulfur atom (S), from a side chain group, for metal ion complexation; Lll is a D-configuration amino acid with an aromatic side chain; R 2 is optionally present, and if present, comprises an amino acid with an aromatic side chain; Ddd is an amino acid that provides an S, from a side chain group, for metal ion complexation; R 3 is an amino acid with an aromatic side chain that provides an N for metal ion complexation; R 4 is a functionality that provides a cationic center; Eee is an uncharged L- or D-configuration amino acid that provides an N for metal ion complexation: R 5 is an amide, substituted amide, ester or carboxylate group, or comprises an L- or D-configuration amino acid; Hhh is an L- or D-configuration cationic amino acid with a positively charged side chain; Iii is an L- or D-configuration amino acid that provides an N for metal ion complexation; Jjj is an L- or D-configuration amino acid with an aromatic side chain; and Kkk is an L- or D-configuration cationic amino acid with a positively charged side chain.