Method for characterising a double stranded nucleic acid using a nano-pore and anchor molecules at both ends of said nucleic acid

1. A method for modifying a target polynucleotide for characterisation using a transmembrane pore in a membrane, comprising:

(a) ligating a Y adaptor to one end of the target polynucleotide; and

(b) attaching to the Y adaptor one or more first anchors for coupling the target polynucleotide to the membrane and attaching directly to the target polynucleotide, one or more second anchors for coupling the polynucleotide to the membrane and thereby providing a modified target polynucleotide;

wherein the strength of coupling of the one or more second anchors to the membrane is greater than the strength of coupling of the one or more first anchor to the membrane.

2. A method according to claim 1 wherein the membrane is chemically modified or functionalised to form the one or more first anchors and/or the one or more second anchors.

3. A method according to claim 1 , wherein the one or more first anchors and one or more second anchors couple to the membrane via hybridisation.

4. A method according to claim 1 , wherein the one or more first anchors and one or more second anchors couple to the membrane via hybridisation and the strength of hybridisation is greater in the one or more second anchors than in the one or more first anchors.

5. A method according to claim 1 wherein one or more anchoring groups which couple each of the first and second anchors to the membrane is the same and the first and second anchors differ in charge, hydrophobicity or by the presence of one or more linkers.

6. A method according to claim 1 wherein the one or more first anchors comprise one or more rigid linkers and the one or more second anchors comprise one or more flexible linkers.

7. A method according to claim 1 wherein the strength of coupling of the one or more second anchors to the target polynucleotide is greater than the strength of coupling of the one or more first anchors to the Y adaptor.

8. A method according to claim 1 , wherein step b) further comprises contacting the polynucleotide provided in step a) with a transmembrane pore such that both strands of the polynucleotide move through the pore and step c) comprises taking one or more measurements as the both strands of the polynucleotide move with respect to the pore wherein the measurements are indicative of one or more characteristics of the strands of the polynucleotides.

9. A method of characterising a target polynucleotide using a transmembrane pore in a membrane, comprising:

a) providing the target polynucleotide with a Y adaptor at one end, wherein the Y adaptor comprises one or more first anchors for coupling the polynucleotide to the membrane, wherein the target polynucleotide comprises one or more second anchors for coupling the polynucleotide to the membrane and wherein the strength of coupling of the one or more second anchors is greater than the strength of coupling of the one or more first anchors to the membrane;

b) contacting the polynucleotide provided in step a) with the transmembrane pore such that at least one strand of the polynucleotide moves through the pore; and

c) taking one or more measurements as the at least one strand of the polynucleotide moves with respect to the pore wherein the measurements are indicative of one or more characteristics of the at least one strand of the polynucleotide and thereby characterising the target polynucleotide.

10. A method according to claim 9 , wherein (a) the membrane is chemically modified or functionalised to form the one or more first anchors and/or the one or more second anchors (b) the one or more first anchors and one or more second anchors couple to the membrane via hybridisation, optionally wherein the strength of hybridisation is greater in the one or more second anchors than in the one or more first anchors (c) one or more anchoring groups which couple each of the first and second anchors to the membrane is the same and the first and second anchors differ in charge, hydrophobicity or by the presence of one or more linkers (d) the one or more first anchors comprise one or more rigid linkers and the one or more second anchors comprise one or more flexible linkers, (e)the strength of coupling of the one or more second anchors to the polynucleotide is greater than the strength of coupling of the one or more first anchors to the Y adaptor, or (f) any combination of (a) to (e).

11. A method according to claim 9 , wherein (i) the one or more second anchors couple to the membrane using cholesterol and the one or more first anchors couple to the membrane using palmitate, (ii) the one or more second anchors couple to the membrane using a mono-acyl species and the one or more first anchors couple to the membrane using a diacyl species, (iii) the one or more first anchors comprise one or more polynucleotide linkers and the one or more second anchors comprise one or more flexible linkers comprising one or more spacer 9 (iSp9) groups or one or more spacer 18 (iSp18), (iv) a combination of (i) and (iii) or (v) a combination of (ii) and (iii).

12. A method to claim 9 , wherein the one or more characteristics of the polynucleotide are measured by electrical measurement and/or optical measurement.

13. A method according to claim 9 , wherein the one or more characteristics of the polynucleotide are measured by electrical measurement and the electrical measurement is a current measurement, an impedance measurement, a tunnelling measurement or a field effect transistor (PET) measurement.

14. A method according to claim 9 , wherein step b) further comprises contacting the polynucleotide provided in step a) with a polynucleotide binding protein such that the protein controls the movement of the at least one strand of the polynucleotide through the pore.

15. A method according to claim 9 , wherein the membrane is an amphiphilic layer or a solid state layer.

16. A method according to claim 9 , wherein the transmembrane pore is a transmembrane protein pore.

17. A method according to claim 9 , wherein the transmembrane pore is a transmembrane protein pore derived from Mycobacterium smegmatis porin (Msp), α-hemolysin (α-HL) or lysenin.

18. A method of characterising a target polynucleotide using a transmembrane pore in a membrane, comprising:

a) providing the target polynucleotide with a Y adaptor at one end, wherein the Y adaptor comprises one or more first anchors for coupling the polynucleotide to the membrane, wherein the polynucleotide comprises one or more second anchors for coupling the polynucleotide to the membrane and wherein the strength of coupling of the one or more second anchors to the membrane is greater than the strength of coupling of the one or more first anchors to the membrane;

b) contacting the polynucleotide provided in step a) with the transmembrane pore, a polymerase and labelled nucleotides such that phosphate labelled species are sequentially released when nucleotides are added to the polynucleotide by the polymerase, wherein the phosphate species contain a label specific for each nucleotide; and

c) detecting the phosphate labelled species using the pore and thereby characterising the target polynucleotide.