Patent ID: 7271249

Claim:
A biosensor, consisting of (i) at least one fragment of a receptor which is protein in nature having one or more disulfide bridges, capable of binding to a ligand via an active site to form a receptor-ligand complex, wherein at least one amino acid residues of the fragment located in the proximity of said active site is naturally present in the form of a cystein (Cys) residue, or is substituted with a Cys residue, and (ii) a fluorophore coupled to said Cys residue, wherein said Cys residue in the receptor-ligand complex: (i) is in direct contact with the ligand, or (ii) is in contact via a water molecule, with the ligand, or (iii) has a solvent accessible surface area (ASA) which is modified by binding of the ligand, the solvent being defined by spheres with a radius comprised in a range from 1.4 to 30 Å and wherein in said receptor, the atom in the γ position of said Cys residue and optionally in the δ position of said Cys residue is accessible to a solvent defined by spheres with a radius of 1.4 Å, wherein said fragment of receptor comprises a polypeptide sequence encoded by pMR1 of sequence SEQ ID NO: 10, deposited with Collection Nationale de Cultures de Microorganismes (CNCM), under the number I-2386, or a polypeptide sequence encoded by pMR1 (VL-S93C) of sequence SEQ ID NO: 11, deposited with CNCM, under the number I-2387, derived from a plasmid pMR1 of sequence SEQ ID NO: 10.