Cyanine dye labelling reagents

1. A compound of formula (I):

wherein:

Z 1 and Z 2 independently represent the carbon atoms necessary to complete a one ring, or two-fused ring aromatic system;

R 1 and R 2 are independently chosen from the group -E-F, C 1 -C 6 alkyl, benzyl either unsubstituted or substituted with sulphonic acid, and the group —(CH 2 ) k —W,

where W is sulphonic acid or phosphonic acid and k is an integer from 1 to 10;

R 3 and R 4 are attached to the Z 1 ring structure and groups R 5 and R 6 are attached to the Z 2 ring structure, and n=1, 2 or 3;

R 3 , R 4 , R 5 and R 6 are independently selected from the group -E-F, hydrogen and sulphonic acid;

each R 7 is independently the group -E-F, hydrogen or two of R 7 together with the group,

form a hydrocarbon ring system having 5 or 6 atoms;

each R 11 , R 12 , R 13 and R 14 is independently a group —(CH 2 ) k —W as defined above, or C 1 -C 6 alkyl;

E is a single bond or a spacer group having a chain from 1-20 linked atoms selected from the group consisting of carbon, nitrogen and oxygen atoms and F is a target bonding group;

wherein F is either:

(i) a reactive group selected from carboxyl, succinimidyl ester, sulpho-succinimidyl ester, isothiocyanate, maleimide, haloacetamide, acid halide, hydrazide, vinylsulphone, dichlorotriazine and phosphoramidite; or

(ii) a functional group selected from hydroxy, amino, sulphydryl, carbonyl (including aldehyde and ketone) and thiophosphate; or

(iii) an affinity tag;

with the provisos that:

(a) one of groups R 1 , R 2 , R 3 , R 4 , R 5 , R 6 and R 7 is the group -E-F;

(b) one or more of R 11 , R 12 , R 13 and R 14 is the group —(CH 2 ) k —W;

(c) the compound of Formula I has from 3 to 5 sulfonic acid groups.

2. A compound according to claim 1 wherein at least two of R 11 , R 12 , R 13 and R 14 are independently —(CH 2 ) k —W.

3. A compound according to claim 1 wherein one of groups R 11 and R 12 and one of groups R 13 and R 14 is the group —(CH 2 ) k —W.

4. A compound according to claim 1 wherein W is sulphonic acid.

5. A compound according to claim 1 wherein —(CH 2 ) k —W is selected from —(CH 2 ) 3 —SO 3 H and —(CH 2 ) 4 —SO 3 H.

6. A compound according to claim 1 wherein Z 1 and Z 2 are selected from phenyl and naphthyl moieties.

7. A compound according to claim 1 wherein said target bonding group F comprises an affinity tag.

8. A compound according to claim 1 wherein said spacer group E is selected from:

—(CHR′) p -Q-(CHR′) r —

where Q is selected from: —CHR′—, —NR′, —O—, —CR′═CR′—, —C(O)—NR′— and —C(O)—O—;

R′ is hydrogen or C 1 -C 4 alkyl, p is 0-5 and r is 1-5.

9. A compound according to claim 8 wherein Q is selected from: —CHR′—, —C(O)—NH— and

where R′ is hereinbefore defined.

10. A compound according to claim 1 wherein said group -E-F comprises a carboxypentyl group.

11. A compound according to claim 1 selected from:

i) 2-{(1E,3E,5E)-5-[1-(5-carboxypentyl)-3-methyl-5-sulpho-3-(4-sulphobutyl)-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-1-ethyl-3-methyl-3-(4-sulphobutyl)-3H-indolium-5-sulphonate;

ii) 2-{(1E,3E,5E)-5-[1-(5-carboxypentyl)-3-methyl-5-sulpho-3-(4-sulphobutyl)-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-3-methyl-1,3-bis(4-sulphobutyl)-3H-indolium-5-sulphonate;

iii) 2-{(1E,3E,5E,7E)-7-[1-(5-carboxypentyl)-3-methyl-5-sulpho-3-(4-sulphobutyl)-1,3-dihydro-2H-indol-2-ylidene]hepta-1,3,5-trienyl}-1-ethyl-3-methyl-3-(4-sulphobutyl)-3H-indolium-5-sulphonate;

iv) 2-{(1E,3E,5E,7E)-7-[5-(carboxymethyl)-3-methyl-1,3-bis(4-sulphobutyl)-1,3-dihydro-2H-indol-2-ylidene]hepta-1,3,5-trienyl}-1-ethyl-3-methyl-3-(4-sulphobutyl)-3H-indolium-5-sulphonate; and

v) 1-benzyl-2-{(1E,3E,5E)-5-[1-(5-carboxypentyl)-3-methyl-5-sulpho-3-(4-sulphobutyl)-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-3-methyl-3-(4-sulphobutyl)-3H-indolium-5-sulphonate.