Methods for detecting allosteric modulators of protein
The present invention discloses, inter alia, methods for labeling a target protein with an SHG-active probe for detection by second harmonic or sum-frequency generation in order to identify agents which bind to an allosteric site on the target protein thereby altering its structural conformation.
1. A method of determining a binding interaction between a target biomolecule and a candidate binding partner comprising:
a. labeling the target biomolecule at a first site with a first second harmonic-active moiety having a net orientation at an interface; contacting the target biomolecule with the candidate binding partner; and detecting a first detectable signal upon binding between the target biomolecule and the candidate binding partner; wherein the first detectable signal is generated by the second harmonic-active moiety using a surface selective technique;
b. separately labeling the target biomolecule at a second site with a second second harmonic-active moiety having a net orientation at an interface; contacting the target biomolecule with the candidate binding partner; and detecting a second detectable signal upon binding between the target biomolecule and the candidate binding partner; wherein the second detectable signal is generated by the second harmonic-active moiety using a surface selective technique;
c. comparing the first detectable signal with the second detectable signal, wherein a difference between the first detectable signal and the second detectable signal indicates a binding interaction between the target biomolecule and the candidate binding partner.
2. The method of claim 1 , wherein the second harmonic-active moiety is selected from the group consisting of PyMPO maleimide, PyMPO-NHS, PyMPO-succinimidyl ester, Badan, and Acrylodan.
3. The method of claim 1 , wherein the second harmonic-active moiety is bound to the target bimolecule by one or more sulfhydryl groups on the surface of the target bimolecule.
4. The method of claim 3 , wherein said one or more sulfhydryl groups are native sulfhydryl groups.
5. The method of claim 3 , wherein said one or more sulfhydryl groups are engineered sulfhydryl groups.
6. The method of claim 2 , wherein the second harmonic-active moiety is bound to the target bimolecule by one or more amine groups on the surface of the target bimolecule.
7. The method of claim 6 , wherein said one or more amine groups are native amine groups.
8. The method of claim 6 , wherein said one or more amine groups are engineered amine groups.
9. The method of claim 1 , wherein the target biomolecule is labeled in situ while bound to a surface.
10. The method of claim 1 , wherein the second harmonic-active moiety is an unnatural amino acid.
11. The method of claim 10 , wherein the unnatural amino acid is Aladan.
12. The method of claim 1 , wherein the first site and the second site is within a binding interface of the target biomolecule.
13. The method of claim 1 , wherein the first site and the second site is outside a binding interface of the target biomolecule.
14. The method of claim 1 , wherein the first site is within a binding interface of the target biomolecule and the second site is outside the binding interface of the target biomolecule.
15. The method of claim 1 , wherein the target biomolecule is a protein, a DNA molecule, an RNA molecule or an oligosaccharide.
16. The method of claim 1 , wherein the interface is selected from the group consisting of:
a glass surface, a polyethylene glycol surface, a supported lipid bilayer surface, a lipid analog bilayer surface, a plastic surface, a metal surface, a latex surface, a rubber surface, a ceramic surface, a polymeric surface, a polypropylene surface, a polyvinylidene difluoride surface, a polyethylene surface.
17. The method of claim 16 , wherein the interface is derivatized with oligo-PEG molecules or lipids.
18. The method of claim 17 , wherein the oligo-PEG molecules or lipids are Ni-NTA-bearing oligo-PEG molecules or Ni-NTA-bearing lipids.
19. The method of claim 1 , wherein the target bimolecule comprises an affinity tag.
20. The method of claim 1 , wherein the difference between the first detectable signal and the second detectable signal is a difference above a noise level.
21. The method of claim 20 , wherein the difference above the noise level between the first detectable signal and the second detectable signal indicates a specific binding interaction between the target biomolecule and the candidate binding partner.