Atomic force microscope integrated with a multiple degrees-of-freedom magnetic actuator

Abstract

The present invention relates to a biomolecular measurement system (1), which enables to measure the intermolecular forces arising from the interaction between two biomolecules or the intramolecular forces within a single biomolecule by using an atomic force microscope (AFM). In the present invention, the cantilever (2) is moved only when the actuator (4) moves the magnetic nanowire (3) and thus moves the molecule attached to the end of the magnetic nanowire (3). Since the cantilever (2) is not moved, fluctuation and disturbance is not created in the liquid containing the biomolecules. Thus, the measurements are made more accurately and with higher resolution. Additionally, by means of the actuator (4), the biomolecules are enabled to be moved upon exertion of magnetic force at any coordinate on x, y and z axes on the nanowire (3), or exertion of torque on two axes.

Claims

1. A biomolecular measurement apparatus, which enables to measure the intermolecular forces arising from the interaction between two biomolecules or the intramolecular forces of a single biomolecule by using an atomic force microscope, comprising: at least one cantilever which remains fixed; at least one cantilever tip to which the single biomolecule can bind; at least one magnetic nanowire to the end of which the single biomolecule can bind; the single molecule which can hind to the end of the magnetic nanowire can bind to an other biomolecule which can bind to the cantilever tip or to the cantilever tip so that the two biomolecules bound together or the single biomolecule can be located between the magnetic nanowire and the cantilever tip, wherein the cantilever tip is pointed and has a radius of curvature at an apex of the cantilever tip that allows binding of only a single biomolecule; at least one laser source which projects light on the cantilever; at least one photodetector on which the light reflected from the cantilever is projected; at least one actuator which, by applying magnetic force to the magnetic nanowire, enables to pull and push the magnetic nanowire on x, y, z axes, wherein, the magnetic nanowire moves by means of the magnetic force exerted by the actuator and enables to move the single biomolecule or the two biomolecules attached to the end of the magnetic nanowire; and the cantilever makes a movement at any coordinate on the x, y and z axes in the direction of the single biomolecule or the two biomolecules without using any actuator, only by means of the movement of the single biomolecule or the two biomolecules actuated by the actuator, wherein the end of the magnetic nanowire that is the area of attachment for the single biomolecule or one of the two biomolecules is produced from gold or polymer, and other parts of the magnetic nanowire are made of a magnetic material which does not bind to the single biomolecule.

2. The biomolecular measurement apparatus of claim 1, wherein the cantilever tip is produced from materials that allow attachment of the single biomolecule or the two biomolecules, which is selected from the group consisting of gold, silicon, silicon nitride or silicon oxide.

3. The biomolecular measurement apparatus of claim 1, wherein the other parts of the magnetic nanowire are made of an item selected from the group consisting of cobalt, iron, nickel or an alloy comprising at least one of these metals.

4. The biomolecular measurement apparatus of claim 1, wherein at least one actuator comprises at least one electromagnet, magnet, Helmhotz coil or at least one of these structures.

5. The bimolecular measurement apparatus of claim 1, wherein the actuator, in order to measure the interaction force between the two biomolecules, one of which is attached to the cantilever tip and the other to the magnetic nanowire, applies magnetic field to the magnetic nanowire and thereby enables the two biomolecules attached to the magnetic nanowire to be moved.

6. The biomolecular measurement apparatus of claim 1, wherein the actuator enables to apply force in at least one preferably three different axes on the magnetic nanowire.

7. The biomolecular measurement apparatus of claim 1, wherein the actuator, by means of a positioner that will be formed by using a plurality of electromagnets, enables the single biomolecule or the two biomolecules attached between the magnetic nanowire and the cantilever tip to be pulled in different directions under magnetic field.

8. The biomolecular measurement apparatus of claim 1, wherein the actuator, in order to measure the intramolecular force of the single biomolecule, one end of the single biomolecule is attached to the cantilever tip and an other end of the single biomolecule is attached to the magnetic nanowire; applies magnetic field to the magnetic nanowire and thereby enables the single biomolecule to unfold or fold.

9. The bimolecular measurement apparatus of claim 1, wherein the movement of the cantilever is a rotational movement.

10. The bimolecular measurement apparatus of claim 9, wherein the cantilever tip is produced from materials that allow attachment of the biomolecules, which is selected from the group consisting of gold, silicon, silicon nitride or silicon oxide.

11. The biomolecular measurement apparatus of claim 9, wherein the other parts of the magnetic nanowire are made of an item selected from the group consisting of cobalt, iron, nickel or an alloy comprising at least one of these metals.

12. The biomolecular measurement apparatus of claim 9, wherein at least one actuator comprises art least one electromagnet, magnet, Helmhotz coil or at least one of these structures.

13. The biomolecular measurement apparatus of claim 9, wherein the actuator, in order to measure the interaction force between the two biomolecules, one of which is attached to the cantilever tip and the other to the magnetic nanowire, applies magnetic field to the magnetic nanowire and thereby enables the two biomolecules attached to the magnetic nanowire to be moved.

14. The biomolecular measurement apparatus of claim 9, wherein the actuator enables to apply torque in least one preferably three different axes on the magnetic nanowire.

15. The biomolecular measurement apparatus of claim 9, wherein the actuator, by means of a positioner that will be formed by using a plurality of electromagnets, enables the single biomolecule or the two biomolecules attached between the magnetic nanowire and the cantilever tip to be pulled in different directions and torque to be applied under rotating magnetic field and angular positioning to be performed.

16. The biomolecular measurement apparatus of claim 9, wherein the actuator, in order to measure the intramolecular force of the single biomolecule, one end of the single biomolecule is attached to the cantilever tip and the other end of the single biomolecule is attached to the magnetic nanowire; applies magnetic field to the magnetic nanowire and thereby enables the single molecule to unfold or fold.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Biomolecular measurement system developed to fulfill the objective of the present invention is illustrated in the accompanying figures, in which,

(2) FIG. 1 is a view of the atomic farce microscope used in the prior art.

(3) FIG. 2 is a view of the biomolecular measurement system that enables measurement of interaction forces between two molecules.

(4) FIG. 3 is a view of the biomolecular measurement system that enables unfolding and folding of a single molecule.

(5) FIG. 4 is a perspective view of the nanowire.

(6) FIG. 5 is a view of a manipulator formed by multiple electromagnets.

(7) FIG. 6 is a representative view of the forces applied to the magnetic nanowirein order to actuate a magnetic nanowireat y axis and xyz axis respectively and the torque applied to the magnetic nanowire.

(8) The components in the figures are given reference numbers as follows: 7. Biomolecular measurement system 8. Cantilever 9. Magnetic nanowire 10. Actuator 11. Laser source 12. Photodetector R. Reflected light I. Incoming light A. Molecule A B. Molecule B

DETAILED DESCRIPTION OF THE INVENTION

(9) A biomolecular measurement system (1), which enables to measure the intermolecular forces arising from the interaction between two biomolecules or the intramolecular forces of a single biomolecule by using an atomic force microscope (AFM), basically comprises at least one cantilever (2) which remains fixed and changes position only upon movement of the molecules without using any actuator, at least one cantilever tip (2.1) having a diameter that allows binding of a single biomolecule, at least one magnetic nanowire (3), to the end of which a single molecule can bind, and which enables to move the molecules, at least one actuator (4) which, by applying magnetic field to the magnetic nanowire (3), enables to pull and push the magnetic nanowire (3) at any coordinate on x, y, z axes and to apply torque on the magnetic nanowire (3) in two different axes, at least one laser source (5) which projects light on the cantilever (2), at least one photodetector (6) on which the light (R) reflected from the cantilever (2) is projected.

(10) The cantilever (2) provided in the biomolecular measurement system (1) of the present invention is fixed and is not moved by any actuator. The cantilever (2) has a pointed cantilever tip (2.1) having a diameter that allows binding of only a single biomolecule. The cantilever tip (2.1) can be a tip produced from materials, such as gold, silicon, silicon nitride or silicon oxide that allow attachment of the biomolecules.

(11) In a preferred embodiment of the invention, in order to measure the forces between two biomolecules (for example molecule A and molecule B), one of the biomolecules is attached to the cantilever tip (2.1) while the other biomolecule binds to the end of the magnetic nanowire (3). The magnetic nanowire (3) is a cylindrical structure preferably having a length of 1 m (micrometer) and a diameter of 100 nm (nanometer). The end of the said magnetic nanowire (3), which is the area of attachment for the biomolecules, is made of gold or polymer, while the other parts can be made of a magnetic material, which does not bind to the molecules, preferably cobalt, iron, nickel or an alloy comprising at least one of these metals. Thus the magnetic nanowire (3) acts as a magnet and can be pushed and pulled by the actuator (4) by applying a magnetic field. An example magnetic nanowire (3) is shown in FIG. 3.

(12) In order to measure the interaction force between the biomolecules binding to the cantilever tip (2.1) and the magnetic nanowire (3) end, these biomolecules should be actuated. An actuator (4) positioned at the lower part of the magnetic nanowire (3) is used for this purpose. This actuator (4) may comprise at least one electromagnet magnet, Helmhotz coil or at least one of these structures. The said actuator (4) is driven by a driver electronics (not shown in the figures), magnetic force is applied to the magnetic nanowire (3) by passing current through the cables wound around the core of the electromagnet, and thus the biomolecules attached between the cantilever tip (2.1) and the magnetic nanowire (3) are moved. Due to the movement of the biomolecules actuated by the actuator (4), the cantilever tip (2.1) and thus the cantilever (2) move at any coordinate on the x, y and z axes in the direction of the biomolecules or make a rotational movement.

(13) A laser source (5) and a photodetector (6) located at the upper part of the cantilever (2) are used to measure the interaction between the biomolecules. A split photodetector can be used as a photodetector (6), for detection of the movement of the cantilever at linear axes and a quadrature photodetector can be used for detection of the torque movement. The incoming light (1) coming from the laser source (5) onto the reflector surface of the cantilever (2) is projected on the photodetector (6) right in the center. The angle of the cantilever with respect to its neutral axis (2) changes due to the movement of the biomolecules and the light reflected from the cantilever (2) is projected not in the center but at a different region of the photodetector (6).

(14) The molecules can be moved at any coordinate on x, y, z axes by using the magnetic nanowires (3). FIG. 6 (left) shows how the magnetic nanowire (3) is pulled downwards by means of the force exerted by the actuator (4) onto the nanowire (3) on y axis. FIG. 6 (middle) shows the force exerted by the actuator (4) onto the magnetic nanowire (3) at any coordinate on x, y and z axes. The force on the magnetic nanowire (3) can be increased by extending the length of the magnetic nanowire (3).

(15) Thanks to use of magnetic nanowires (3) instead of magnetic spheres, in addition to the force in at least one preferably three different axes, torque in least one preferably three different axes can also be applied by the actuator (4) on the magnetic nanowire (3). FIG. 6 (right) shows the torque applied to the magnetic nanowire (3). Applying torque on the magnetic nanowire (3) enables for example double helix DNAs to recoil. By means of an actuator (4) functioning as a positioner that will be formed by electromagnets, the molecules attached between the magnetic nanowire (3) and the cantilever tip (2.1) can be pulled in different directions and torque can be applied under rotating magnetic field and angular positioning can be performed. To this end, the magnetic nanowire (3) can be positioned precisely in a spherical working field by means of an actuator (4) that will be formed by bringing eight electromagnets together. For this reason, molecular folding/unfolding/refolding mechanisms can be completely performed by the actuators (4) formed with the said electromagnets.

(16) In another embodiment of the invention, instead of measuring the interactions between two biomolecules, it is enabled to elucidate unfolding/folding pathways and dynamics of a single biomolecule such as a protein. For example, proteins unfold like a string when they take part in enzymatic interaction, and then when they are done, they refold. Some critical diseases occur when the proteins, after unfolding and fulfilling their function, get misfolded. For example, Alzheimer is one of these diseases. If a typical protein in the brain is unfolded, carries out its function and then folds incorrectly, it cannot unfold again. Examination of this is very important in single molecule level.

(17) In order to examine the intramolecular forces of a single biomolecule, one end of the said biomolecule is attached to the magnetic nanowire (3) while the other end thereof is attached to the cantilever tip (2.1). As in the previous application, the magnetic nanowire (3) is subjected to the magnetic field formed by passing current through the coils of electromagnets (4) and the magnetic nanowire (3) is moved forward and backward. Thus the biomolecule at the end of the magnetic nanowire (3) is enabled to be unfolded and folded. The biomolecule moves the cantilever tip (2.1) when being unfolded and folded, and this movement enables the light projected by the laser (5) on the reflector surface of the cantilever (2) to be reflected at a different angle and to be projected to a position which is different from the position where the reflected light (R) is first projected on the photodetector. Pathways and dynamics of unfolding and folding of the biomolecule can be elucidated also by calculation of the difference of position of the light projected on the photodetector (6).

(18) In the biomolecular measurement system (1) of the present invention, thanks to not using an actuator to move the cantilever (2), a fluctuation is not created in the liquid in which the biomolecules are present. This in turn prevents the measurements from getting adversely affected.