Detectable threading intercalator

1. A threading intercalator of general formula I:

IG 1 -DG-IG 2 -(DG-IG 3 ) n   (I)

wherein

IG 1 , IG 2 and IG 3 are the same or different and each of IG 1 , IG 2 and IG 3 is an intercalating group that is a naphthalene imide derivative or a naphthalene diimide derivative, with at least one of IG 1 , IG 2 and IG 3 being a napthalene diimide derivative having a structure of formula V:

R 1 is a group which is capable of forming a coordinative bond with the detectable group and has a structure of formula IV:

—R 6 -AG  (IV)

wherein

R 6 is a branched or unbranched, saturated or unsaturated C 1 -C 10 alkylene; or a branched or unbranched, saturated or unsaturated C 1 -C 10 heteroalkylene having from 1 to 3 heteroatoms selected from the group consisting of N, O, S and P; and

AG is a saturated or unsaturated 5 to 10-membered heterocyclic group having from 1 to 3 heteroatoms selected from the groups consisting of N, O, S and P;

R 2 is H, NR 3 R 4 , CONR 3 R 4 , COOR 5 , an optionally branched C 1 -C 10 alkyl or an optionally branched C 2 -C 10 alkene, which C 1 -C 10 alkyl and C 2 -C 10 alkene are optionally substituted by one or more substituents selected from the group consisting of (i) a 5 to 10 membered heterocyclic group having from 1 to 3 heteroatoms selected from the group consisting of N, O, S, and P; (ii) a C 5 -C 14 saturated or unsaturated cyclic group; (iii) a C 6 -C 14 aryl group; (iv) NR 3 R 4 ; (v) CONR 3 R 4 ; and (vi) COOR 5 ;

R 3 , R 4 and R 5 are each independently selected from the group consisting of H, C 1 -C 6 alkyl and C 2 -C 6 alkene, and when the R 2 group contains a N atom, R 2 optionally forms a salt;

DG is a catalytic, electrochemical, a chemiluminescent or an electrochemiluminescent detectable group having a structure of formula II:

-M[(L) n′ ]-  (II)

wherein

M represents a metal selected from the group consisting of Ru, Fe, Co, Cu and Os;

L is a coordinative binding ligand that is a C 5 -C 30 heterocyclic group comprising from 1 to 6 heteroatoms selected from the group consisting of N, O, S and P, optionally substituted by 1 to 6 groups independently selected from C 1 -C 6 alkyl, C 2 -C 6 alkene and halogen; and

n′ is an integer from 1 to 6; and

n is 0 or 1.

2. The threading intercalator according to claim 1 , wherein n is 0.

3. The threading intercalator according to claim 1 , wherein the detectable group is electrochemiluminescent.

4. The threading intercalator according to claim 1 , wherein the metal has an oxidation state of +2, +3 or +4.

5. The threading intercalator according to claim 1 , wherein the ligand is bipyridine, biimidazole, 1,10-phenanthroline or dipyridophenazine.

6. The threading intercalator according to claim 1 , wherein the ligand is bipyridine.

7. The threading intercalator according to claim 1 , wherein the detectable group is Ru(bipyridine) 2 2+ .

8. The threading intercalator according to claim 1 , wherein the naphthalene imide derivative has a structure of formula III:

wherein R 1 is as defined in claim 1 for formula V and is independently selected from R 1 in formula V.

9. The threading intercalator according to claim 1 , or claim 8 wherein AG in formula V or formula III is pyridinyl, bipyridinyl, imidazolyl or biimidazolyl.

10. The threading intercalator according to claim 1 , wherein R 2 is —(CH 2 ) 3 -imidazole, —NH 2 , —CO 2 H, —CH 3 , —(CH 2 ) 2 N(CH 3 ) 2 , —(CH 2 ) 4 CH(NH 2 )(CONH 2 ), —CH(CONH-adamantyl)(CH 2 ) 4 NH 2 , —CH(CH 3 )(CH 2 ) 3 N(C 2 H 5 ) 2 , —(CH 2 )N(CH 3 ) 2 , —(CH 2 )N + (CH 3 ) 3 I − , —(CH 2 ) 3 N(CH 3 ) 2 , —(CH 2 ) 4 (CH)(CONH 2 )(NH 2 ), —CH(CONH 2 ) (CH 2 ) 4 NH 2 , —CH(CONH-adamantyl)(CH 2 ) 4 NH 2 , —CH(CH 3 )(CH 2 ) 3 N(C 2 H 5 ) 2 , —CH(CH 3 ) (CH 2 ) 3 N + (C 2 H 5 ) 2 (CH 3 )I − .

11. The threading intercalator according to claim 1 , wherein R 1 and R 2 are both —(CH 2 ) 3 -imidazole.

12. The threading intercalator according to claim 1 , which has a structure of formula VII:

13. The threading intercalator according to claim 1 , which has a structure of formula VIII:

14. A complex comprising a double stranded nucleic acid molecule and a threading intercalator as claimed in claim 1 , wherein the threading intercalator is intercarated in said double stranded nucleic acid molecule.

15. A process for detecting a single stranded nucleic acid molecule complementary to a nucleic acid probe immobilized onto an electrode substrate, which comprises the steps of:

(a) contacting the probe molecules with an oligo- or poly-nucleotide sample in the presence of a threading intercalator as claimed in claim 1 to form by hybridization a complex comprising a double stranded hybrid of the probe molecules and the complementary single stranded nucleic acid molecules in the oligo- or poly-nucleotide sample, in which hybrid is intercalated the threading intercalator;

(b) exciting the complex formed in step (a) by irradiating the complex with a light source or applying an electric current to the electrode; and

(c) detecting photoluminescence or a change in voltametric peak current caused by a detectable group comprised in the threading intercalator.

16. A process for detecting a single stranded nucleic acid molecule complementary to a nucleic acid probe immobilized onto an electrode substrate, which comprises the steps of:

(a) contacting the probe molecules with an oligo- or poly-nucleotide sample to form by hybridization a complex comprising a double stranded hybrid of the probe molecules and the complementary single stranded nucleic acid molecules in the oligo- or poly-nucleotide sample;

(b) contacting a threading intercalator as claimed in claim 1 with the complex formed in step (a) so as to intercalate the threading intercalator into the complex formed in step (a);

(c) exciting the complex formed in step (b) by irradiating the complex with a light source or applying an electric current to the electrode; and

(d) detecting photoluminescence or a change in voltametric peak current caused by a detectable group comprised in the threading intercalator.

17. A kit for detecting a single stranded nucleic acid molecule complementary to a nucleic acid probe, which comprises an electrode substrate on which is immobilized the nucleic acid probe, and a threading intercalator as claimed in claim 1 .