Formation of hairpins in situ using force-induced strand invasion

1. A method for preparing a hairpin nucleic acid comprising a sequence of interest, said method comprising the steps of:

(a) providing a nucleic acid HP1 , said nucleic acid HP1 comprising:

a first end bound to a first surface;

a single-stranded sequence A linked to said first end,

a single-stranded sequence A′ hybridized to said sequence A, wherein said sequence A and said sequence A′ are not covalently linked; and form a double stranded region compromising the sequence A and the sequence A′;

a single-stranded sequence C linked to said sequence A′;

a second end linked to said sequence C, wherein said second end is bound to a second surface;

wherein one of the first surface and the second surface is a movable surface and the first surface and the second surface are different surfaces;

b) providing at least one nucleic acid HP2, said nucleic acid HP2 comprising:

a double-stranded region comprising the sequence of interest,

a loop linked to a first end of said double-stranded region that links the two strands of said double-stranded region,

a single-stranded region having the sequence A linked to a first strand of a second end of said double-stranded region, said single-stranded region having the sequence A being linked to a single-stranded sequence C′, the sequence C′ being complementary to the sequence C;

a single-stranded polynucleotide having the sequence A′ linked to a second strand of the second end of said double-stranded region wherein the sequence A hybridizes to the sequence A′and form a double stranded region comprising the sequence A and the sequence A′;

c) denaturing said nucleic acid HP1 from step a) in the presence of said nucleic acid HP2 from step b) by moving one surface of the first surface and the second surface away from another surface of the first surface and the second surface by applying a tension of at least 3 pN to the moveable surface, such that said double stranded region comprising the sequence A and the sequence A′ of said nucleic acid HP1 are completely denatured; and

d) obtaining said hairpin nucleic acid, wherein said hairpin nucleic acid is formed by hybridizing said nucleic acid HP1 to said nucleic acid HP2 in the presence of the tension.

2. The method of claim 1 , wherein:

said sequence A of said nucleic acid HP1 is linked to a single-stranded sequence D, said sequence D being located between said sequence A and said first surface and said sequence A linked to said first end bound to the first surface by said sequence D; and

said sequence A′ of said nucleic acid HP2 is linked to a single-stranded region having sequence D′, wherein the sequence D′ is complementary to the sequence D of said nucleic acid HP1.

3. The method of claim 2 , wherein each of the sequence D and the sequence D′ comprises at least 10 nucleotides.

4. The method of claim 2 , wherein each of the sequence D and the sequence D′ comprises at least 12 nucleotides.

5. The method of claim 2 , wherein each of the sequence D and the sequence D′ comprises at least 13 nucleotides.

6. The method of claim 1 , wherein the tension of at least 3 pN is a tension of at least 4 pN.

7. The method of claim 1 , wherein more than one molecule of said nucleic acid HP1 is attached to one of the first surface and the second surface.

8. The method of claim 1 , wherein said at least one nucleic acid HP2 comprises a plurality of distinct nucleic acid molecules.

9. The method of claim 1 , wherein each of the sequence A and the sequence A′ comprises at least 30 nucleotides.

10. The method of claim 1 , wherein each of the sequence C and the sequence C′ comprises at least 10 nucleotides.

11. The method of claim 1 , further comprising:

e) completely denaturing the hairpin structure in the hairpin nucleic acid by moving one surface of the first surface and the second surface away from another surface of the first surface and the second surface and obtaining a nucleic acid molecule without the hairpin structure;

f) measuring the distance (Z high ) between the two ends of the nucleic acid molecule without the hairpin structure obtained in step e);

g) hybridizing a single-stranded nucleic acid molecule with said nucleic acid molecule without the hairpin structure obtained in step e) and generating a complex;

h) renaturing said hairpin structure of said complex from step g);

i) detecting a blockage of the renaturation of said hairpin structure of said complex, wherein said blockage is caused by said single-stranded nucleic acid molecule of said complex; and

j) determining the position of said blockage with respect to one end of the hairpin nucleic acid, said determination comprising the steps of:

measuring distance (z) between the two ends of the hairpin nucleic acid which are attached to the first surface and the second surface during the period of said blockage,

comparing z and Z high , and

determining the position of the blockage with respect to one end of the hairpin nucleic acid.

12. The method of claim 1 , further comprising:

e) completely denaturing the hairpin structure in the hairpin nucleic acid by moving one surface of the first surface and the second surface away from another surface of the first surface and the second surface and obtaining a nucleic acid molecule without the hairpin structure;

f) measuring the distance (Z high ) between the two ends of the nucleic acid molecule without the hairpin structure obtained in step e);

g) hybridizing a single-stranded nucleic acid molecule with said nucleic acid molecule without the hairpin structure obtained in step e) and generating a complex;

h) renaturing said hairpin structure of said complex from step g);

i) detecting a blockage of the renaturation of said hairpin structure of said complex, wherein said blockage is caused by said single-stranded nucleic acid molecule of said complex;

j) determining the position of said blockage with respect to one end of the hairpin nucleic acid, said determination comprising the steps of:

measuring distance (z) between the two ends of the hairpin nucleic acid which are attached to the first surface and the second surface during the period of said blockage,

comparing z and Z high , and

determining the position of the blockage with respect to one end of the hairpin nucleic acid; and

k) determining the duration of said blockage.

13. The method of claim 1 , further comprising:

e) completely denaturing the hairpin structure in the hairpin nucleic acid by moving one surface of the first surface and the second surface away from another surface of the first surface and the second surface and obtaining a nucleic acid molecule without the hairpin structure;

f) measuring the distance (Z high ) between the two ends of the nucleic acid molecule without the hairpin structure obtained in step e);

g) contacting a single-stranded nucleic acid-binding protein with said nucleic acid molecule without the hairpin structure obtained in step e) and generating a complex;

h) renaturing said hairpin structure of said complex from step g) in the presence of said protein;

i) detecting a blockage of the renaturation of the hairpin structure, wherein said blockage is caused by binding said protein to a single-stranded region of said nucleic acid molecule without the hairpin structure;

j) determining the position of said blockage with respect to one end of the hairpin nucleic acid, said determination comprising the steps of:

measuring distance (z) between the two ends of the hairpin nucleic acid which are attached to the first surface and the second surface during the period of said blockage,

comparing z and Z high , and

determining the position of the blockage with respect to one end of the hairpin nucleic acid; and

k) determining the duration of said blockage.

14. The method of claim 1 , further comprising:

e) completely denaturing the hairpin structure in the hairpin nucleic acid by moving one surface of the first surface and the second surface away from another surface of the first surface and the second surface and obtaining a nucleic acid molecule without the hairpin structure;

f) measuring the distance (Z high ) between the two ends of the nucleic acid molecule without the hairpin structure obtained in step e);

g) contacting a double-stranded nucleic acid-binding protein and a single-stranded nucleic acid molecule with said nucleic acid molecule without the hairpin structure obtained in step e) and generating a complex, wherein the single-stranded nucleic acid molecule hybridizes to said nucleic acid molecule without the hairpin structure;

h) renaturing said hairpin structure of said complex from step g) in the presence of said protein;

i) detecting a blockage of the renaturation of the hairpin structure, wherein said blockage is caused by binding said protein to a double-stranded region in the complex formed by the single-stranded nucleic acid molecule and a single stranded region generated by complete denaturation of the hairpin structure;

j) determining the position of said blockage with respect to one end of the hairpin nucleic acid, said determination comprising the steps of:

measuring distance (z) between the two ends of the hairpin nucleic acid which are attached to the first surface and the second surface during the period of said blockage,

comparing z and Z high , and

determining the position of the blockage with respect to one end of the hairpin nucleic acid; and

k) determining the duration of said blockage.

15. The method of claim 1 , wherein the tension of at least 3 pN is a tension of at least 5 pN.

16. The method of claim 1 , wherein the tension of at least 3 pN is a tension of at least 6 pN.

17. The method of claim 1 , wherein each of the sequence A and the sequence A′ comprises at least 35 nucleotides.

18. The method of claim 1 , wherein each of the sequence C and the sequence C′ comprises at least 12 nucleotides.