Patent ID: 7662973

Claim:
A method for increasing the fluorescence of a cyanine dye molecule which includes at least one NO 2 group, comprising reducing said at least one NO 2 group of said cyanine dye to NHOH or NH 2 in a nitroreductase reporter gene assay; wherein the cyanine dye molecule is of Formula Ia, Formula Ib or Formula Ic: wherein groups R 3 , R 4 , R 5 and R 6 are attached to the rings containing X and Y or, optionally, are attached to atoms of the Z 1 and Z 2 ring structures; Z 1 and Z 2 each represent a bond or the atoms necessary to complete one or two fused aromatic rings each ring having five or six atoms, selected from the group consisting of carbon atoms, oxygen atoms, nitrogen atoms and sulphur atoms wherein no more than two atoms in each ring are oxygen, nitrogen, or sulphur; X and Y independently represent a carbon atom substituted with two C1-C4 alkyl residues that may be linked to form a C4-C5 ring system or are selected from the group consisting of oxygen, sulphur, selenium, —CH═CH— and N—W wherein N is nitrogen and W is selected from hydrogen, a group —(CH 2 ) m R 8 where m is an integer from 1 to 26 and R 8 is selected from the group consisting of hydrogen, amino, aldehyde, acetal, ketal, halo, cyano, aryl, heteroaryl, hydroxyl, sulphonate, sulphate, carboxylate, phosphonate, polyethylene glycol, substituted amino, quaternary ammonium, nitro, primary amide, substituted amide, and groups reactive with amino, hydroxyl, carbonyl, carboxyl, phosphoryl, and sulphydryl groups; groups R 3 , R 4 , R 5 , R 6 and R 7 are independently selected from the group consisting of hydrogen, substituted or unsubstituted C 1 -C 4 alkyl, OR 9 , COOR 9 , nitro, amino, acylamino, quaternary ammonium, phosphate, sulphonate and sulphate, where R 9 is substituted or unsubstituted and selected from H, C 1 -C 4 alkyl, amino, aldehyde, acetal, ketal, halo, cyano, aryl, heteroaryl, hydroxyl, sulphonate, sulphate, carboxylate, substituted amino, quaternary ammonium, nitro, primary amide, substituted amide, and groups reactive with amino, hydroxyl, carbonyl, carboxyl, phosphoryl, and sulphydryl groups; groups R 1 and R 2 are C 1 -C 10 alkyl which may be unsubstituted or substituted; and further wherein at least one of the groups R 1 , R 2 , R 3 , R 4 , R 5 , R 6 and R 7 includes at least one nitro group which reduces the fluorescence emission of said dye such that it is essentially non-fluorescent.