The construction of chimeric proteins is an elegant approach for FRET analysis in living cells (e.g. Cameleon or chimeric peptides for substrate-enzyme reactions). A chimeric protein useful for FRET analysis usually is a molecule, which is labelled with one fluorophore on the N-terminal end of the protein and with the other fluorophore on the C-terminal end of the protein. By enzymatic cleavage or conformational change of the protein the distance between the FRET partners changes. Depending on the construction and functionality of the protein the probability of FRET increases or decreases.