Abstract: A method for measurement of an activation state of G-protein-coupled receptors comprises: supplying a human biological sample; preparing a fluorescent donor probe comprising an anti-GPCR Fab fragment or antibody and a fluorophore group linked via amide bond to an amino group of the N-terminal amino acid of the light chain and/or of the N-terminal amino acid of the heavy chain of the Fab fragment or antibody; preparing a fluorescent acceptor probe comprising an anti-G-protein and/or anti-arrestin Fab fragment or antibody and a fluorophore group linked via amide bond to an amino group of the N-terminal amino acid of the light chain and/or of the N-terminal amino acid of the heavy chain of the Fab fragment or antibody; setting the human biological sample in contact with the fluorescent acceptor probe and with the fluorescent donor probe; sensing the activation state of the GCPR receptors by means of fluorescence microscopy techniques.

Abstract: An antibody or Fab fragment, wherein at least one amino group of the N-terminal amino acid of the light chain and/or of the N-terminal amino acid of the heavy chain is bound by an amidic bond to a molecule comprising a fluorophore group A, wherein said bond constitutes at least 70% of the total binding of said molecule to said antibody or Fab.

Abstract: An antibody or Fab fragment, wherein at least one amino group of the N-terminal amino acid of the light chain and/or of the N-terminal amino acid of the heavy chain is bound by an amidic bond to a molecule comprising a fluorophore group A, wherein said bond constitutes at least 70% of the total binding of said molecule to said antibody or Fab.