A compound represented by the following formula, or a pharmacologically acceptable salt thereof: wherein A 1 and A 2 each independently represent an amino acid residue selected from phenylalanine, methionine, valine, leucine, isoleucine, proline, tyrosine, glycine, alanine and tryptophan, m is an integer of 0 to 3, A 3 represents an amino acid residue having an amino group or a carboxy group on a side chain thereof, A 4 represents an amino acid residue, n is an integer of 0 to 3, R 1 represents a group binding to the amino group or the carboxy group on the side chain of A 3 and having a functional group capable of binding to a target molecule recognition element being a polypeptide or a linking group thereof, which is at least one kind of functional group selected from the group consisting of a carboxy group or an active ester thereof, the active ester being selected from a chloroacetyl group, a bromoacetyl group, and an iodoacetyl group; a group having a C=C bond selected from a maleimide group and an acryloyl group; a carbamoyl group, an isothiocyanate group and an amino group, or a hydrogen atom of the amino group or the carboxy group on the side chain of A 3, provided that R 1 may form a heterocyclic group having 3 to 10 carbon atoms including a nitrogen atom of the amino group on the side chain of A 3 as a ring-constituting atom, and L represents a group represented by the formula: wherein R 3, R 4, R 5, and R 6 each independently represent a hydrogen atom, a -CH 2 COOR 10 group, or a hydrocarbon group having 1 to 8 carbon atoms, R 10 represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and the symbol * represents a binding site, provided that at least three of R 3, R 4, R 5, and R 6 each represent a -CH 2 COOH group, or a group represented by the formula: wherein the symbol * represents a binding site. A 1 and A 2 each independently represent an amino acid residue selected from phenylalanine, methionine, valine, leucine, isoleucine, proline, tyrosine, glycine, alanine and tryptophan, m is an integer of 0 to 3, A 3 represents an amino acid residue having an amino group or a carboxy group on a side chain thereof, A 4 represents an amino acid residue, n is an integer of 0 to 3, R 1 represents a group binding to the amino group or the carboxy group on the side chain of A 3 and having a functional group capable of binding to a target molecule recognition element being a polypeptide or a linking group thereof, which is at least one kind of functional group selected from the group consisting of a carboxy group or an active ester thereof, the active ester being selected from a chloroacetyl group, a bromoacetyl group, and an iodoacetyl group; a group having a C=C bond selected from a maleimide group and an acryloyl group; a carbamoyl group, an isothiocyanate group and an amino group, or a hydrogen atom of the amino group or the carboxy group on the side chain of A 3, provided that R 1 may form a heterocyclic group having 3 to 10 carbon atoms including a nitrogen atom of the amino group on the side chain of A 3 as a ring-constituting atom, and L represents a group represented by the formula: wherein R 3, R 4, R 5, and R 6 each independently represent a hydrogen atom, a -CH 2 COOR 10 group, or a hydrocarbon group having 1 to 8 carbon atoms, R 10 represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and the symbol * represents a binding site, provided that at least three of R 3, R 4, R 5, and R 6 each represent a -CH 2 COOH group, or a group represented by the formula: wherein the symbol * represents a binding site.