Patent ID: 7414023

Claim:
A peptide represented by formula (III): CX 1 X 2 X 3 CX 4 X 5 X 6 X 7 CX 8 X 9 C (III), wherein X 1 is V or A, X 2 is A, S, E, T, V or Q, X 3 is Y, each of X 4 , X 5 , X 6 and X 7 is independently any amino acid, X 8 is Y or W, and X 9 is V, T, M, Y, G or F, wherein at least one pair of cysteines which are separated by at least two amino acids are interconnected by a disulfide bond to form a cyclic structure defined by the cysteines, intermediary amino acids and the disulfide bond, and wherein said peptide selectively binds to free prostate specific antigen.