
A peptide is disclosed which is represented by the formula: wherein one of X and Y stands for a single bond, an amino acid residue selected from the class consisting of Asp, Glu, Lys and a divalent group represented by the formula, ##STR1## (wherein n stands for an integer in the range of 1 to 17), or a peptide residue formed by peptide linkage of two to ten amino acid residues of at least one species selected from the class mentioned above, the other of X and Y stands for an amino acid residue ...











