Dye pair for fluorescence resonance energy transfer (FRET) measurements

1. Method for determining an interaction between biomolecules labelled with a donor or acceptor, respectively, based on fluorescence resonance energy transfer and measurement of resulting fluorescence wherein metallic chelate complexes containing metal ions from groups VII and VIII of transition elements are used as energy donors in combination with low molecular fluorophores having a molecular weight between 309 Da and 3000 Da as energy acceptors.

2. Method as claimed in claim 1 , wherein the lower molecular fluorophores have an absorption maximum between 600 nm and 750 nm.

3. Method as claimed in claim 1 , wherein the low molecular fluorophores have a molecular weight of <2000 Da.

4. Method as claimed claim 1 , wherein the fluorophores are selected from the group consisting of xanthenes, cyanins, rhodamines and oxazines.

5. Method as claimed in claim 1 , wherein a rhodamine of general formula I is used as the fluorophore

in which R1 and R13 are the same or different and denote: hydrogen, alkyl with 1 to 20 carbon atoms, polyoxyhydrocarbyl units, phenyl, phenylalkyl with 1 to 3 carbon atoms in the alkyl chain wherein the alkyl or/and phenyl residues can be substituted by one or more hydroxy, halogen, sulpho, carboxy or alkoxycarbonyl groups in which alkoxy can have 1 to 4 carbon atoms;

R7 denotes an alkyl group substituted by at least one halogen with 1 to 20, preferably 1 to 7 carbon atoms or a phenyl group which is substituted by a carboxy or alkoxycarbonyl group in the o-position relative to the carbon atom bound to the pentacyclic ring system and by at least one halogen and wherein alkoxy can have 1 to 4 carbon atoms, or a carboxyalkyl group or a carboxymethyleneoxy-alkyloxy group;

the two bonds marked by the dashed lines mean that the two carbon atoms linked by the dashed bond can be linked together by a single or double bond;

wherein R14, R15 and the other positions of the pentacyclic basic structure that are not labelled with specific symbols can be substituted by alkyl groups with 1 to 20 carbon atoms; wherein X is a counterion and wherein at least one of the residues R1, R7 or/and R13 is coupled to a biomolecule.

6. Method as claimed in claim 5 , wherein the substituent R7 is an electron-attracting residue.

7. Method as claimed in claim 1 , wherein an oxazine of general formula II is used as the fluorophore

in which R1, R4, R5, R6, R7, R10 denote hydrogen, alkyl, hydroxy, halogen, carboxyl, sulfonyl or amino and

R2, R3 denote hydrogen, alkyl, alkoxy, polyoxyhydroxycarbonyl units, phenyl, phenylalkyl which can be substituted by hydroxy, sulfonyl, carboxy, amino, alkoxycarbonyl, in which R2 and R1 or R3 and R4 can form a saturated or unsaturated C4 or C5 bridge and

R8, R9 denote hydrogen, alkyl, alkoxy, polyoxyhydroxycarbonyl units, phenyl, phenylalkyl which can be substituted by hydroxy, sulfonyl, carboxy, amino, alkoxycarbonyl, in which R2 and R1 or R3 and R4 can form a saturated or unsaturated C4 or C5 bridge and

wherein at least one of the residues R2, R3, R8 or R9 represents a non-bridge-forming residue that is coupled to a biomolecule and wherein at least one of the residues R2, R3, R8 and R9 represents a bridge-forming residue which can be optionally substituted by alkyl.

8. Method as claimed in claim 1 , wherein the metal chelate complex is a ruthenium complex.

9. Method as claimed in claim 1 , wherein a time-resolved measurement of fluorescence is carried out.

10. Method as claimed in claim 1 , wherein the fluorescence is measured by a phase modulation technique.

11. Reagent kit for detecting an analyte in a sample, comprising at least one biomolecule labelled with a metal chelate complex containing metal ions from groups VII and VIII of transition elements and at least one further biomolecule which is labelled with a low molecular fluorophore.

12. Reagent combination for determining interaction between partners of a bioaffine binding pair, comprising one partner of a bioaffine binding pair that is labelled with a metal chelate complex containing metal ions from groups VII and VIII of transition elements and another partner of a bioaffine binding pair is labelled with a lower molecular fluorophore having a MW between 300 Da and 3000 Da.