Patent ID: 8445291

Claim:
A method for detecting a target substance, comprising: bringing into contact with each other (a) a tag comprising a polypeptide forming an α-helix structure, the tag bound to the target substance, and (b) a probe comprising a compound bound to a fluorescent dye; and measuring the fluorescence emitted by the fluorescent dye, wherein a binding of the α-helix structure of the tag to the compound of the probe induces a spectral change in the fluorescence emitted by the fluorescent dye, wherein the compound of the probe comprises a polypeptide forming an α-helix structure, and wherein the polypeptide of the tag comprises a sequence represented by the following structural formula (2) and the polypeptide of the probe comprises a sequence represented by the following structural formula (3): Tag: {X 1 -ε 1 -α-X 4 -β-γ-X 7 }{X 1 -ε 2 -α-X 4 -β-γ-X 7 }{X 1 -ε 3 -α- (2) X 4 -β-γ-X 7 }{X M }{X 1 -γ-β-X 4 -β-ε 3 -X 7 }{X 1 -γ-β-X 4 -β- e 2 -X 7 }{X 1 -γ-β-X 4 -β-ε 1 -X 7 } Probe: {X 1 -γ-α-X 4 -α-σ 1 -X 7 }{X 1 -γ-α-X 4 -α-σ 2 -X 7 }{X 1 -γ-α- (3) X 4 -α-σ 3 -X 7 } wherein α is an acidic amino acid or a basic amino acid; β is a basic amino acid when α is an acidic amino acid, and is an acidic amino acid when α is a basic amino acid; γ is a hydrophobic amino acid; at least one of σ 1 to σ 3 is a molecule bound to a fluorescent dye and the rest of σ 1 to σ 3 are each a hydrophobic amino acid; ε 1 is each independently one of glycine, alanine, valine, serine, threonine and asparagine when σ 1 is the fluorescent dye-bound molecule, and is each independently a hydrophobic amino acid when σ 2 is a hydrophobic amino acid; ε 2 is each independently one of glycine, alanine, valine, serine, threonine and asparagine when σ 2 is the fluorescent dye-bound molecule, and is each independently a hydrophobic amino acid when σ 2 is a hydrophobic amino acid; ε 3 is each independently one of glycine, alanine, valine, serine, threonine and asparagine when σ 3 is the fluorescent dye-bound molecule, and is each independently a hydrophobic amino acid when σ 3 is a hydrophobic amino acid; X 1 , X 4 and X 7 are each any amino acid; and X M is a linker peptide comprising M amino acids where M represents a number.