Methods of assaying proteins
Methods and systems for identifying a protein within a sample are provided herein. A panel of antibodies are acquired, none of which are specific for a single protein or family of proteins. Additionally, the binding properties of the antibodies in the panel are determined. Further, the protein is iteratively exposed to a panel of antibodies. Additionally, a set of antibodies which bind the protein are determined. The identity of the protein is determined using one or more deconvolution methods based on the known binding properties of the antibodies to match the set of antibodies to a sequence of a protein.
1. A method of determining characteristics of a plurality of n protein molecules, the method comprising:
obtaining a substrate having the plurality of the n protein molecules conjugated to the substrate such that each individual protein molecule of the plurality of the n protein molecules is spatially separated from each other protein molecule of the plurality of the n protein molecules and wherein each protein molecule of the plurality of the n protein molecules has a unique, optically resolvable, spatial address;
applying one or more fluids to the substrate, wherein the one or more fluids comprise a series of m affinity reagents, wherein each of the m affinity reagents comprises a known degree of nonspecificity and is configured to bind to one or more epitopes of at least one protein molecule of the plurality of the n protein molecules, and wherein each of the m affinity reagents is linked to an identifiable tag, wherein n is larger than m, and n and m are positive integers greater than 1, and n is at least 5 times greater than m;
after each application of the one or more fluids to the substrate, performing the following:
observing one or more signals of the identifiable tags linked to affinity reagents that are bound to the one or more epitopes of the individual protein molecules of the plurality of the n protein molecules;
identifying one or more unique spatial addresses of the substrate having the one or more observed signals;
determining that each protein molecule of the plurality of the n protein molecules having an identified unique spatial address contains the one or more epitopes having bound affinity reagents linked to identifiable tags having the one or more observed signals; and
determining the characteristics of each protein molecule of the plurality of the n protein molecules containing one or more epitopes having bound affinity reagents linked to identifiable tags having the one or more observed signals using one or more deconvolution methods based on the known binding properties of the affinity reagents to match the set of affinity reagents to the protein characteristic, thereby determining the characteristic of the protein.
2. The method of claim 1 , wherein one or more of the m affinity reagents is specific to an individual protein or protein family.
3. The method of claim 2 , wherein one or more of the m affinity reagents is specific to one or more individual distinguishable proteins.
4. The method of claim 1 , wherein each of the m affinity reagents recognizes a family of one or more epitopes that are present in more than one proteins.
5. The method of claim 1 , wherein at least one of the m affinity reagents binds to at least one epitope which is conformational or linear.
6. The method of claim 1 , wherein one or more of the m affinity reagents recognizes an epitope which comprises a contiguous amino acid sequence.
7. The method of claim 1 , further comprising:
determining the encoding gene of each protein molecule of the plurality of the n protein molecules to a threshold degree of accuracy based on the determined one or more epitopes within the protein molecule.
8. The method of claim 1 , wherein the m affinity reagents comprise more than 10 affinity reagents.
9. The method of claim 1 , further comprising using at least one affinity reagent which binds a single protein, single protein isoform, or post-translational modification.
10. The method of claim 1 , further comprising:
determining the encoding gene of each protein molecule of the plurality of the n protein molecules to a threshold degree of accuracy based on the pattern of binding of the affinity reagents.
11. The method of claim 1 , wherein the substrate comprises a flow cell.
12. The method of claim 1 , wherein some protein molecules of the plurality of the n protein molecules are conjugated to the substrate using an activatable linker.
13. The method of claim 1 , wherein some protein molecules of the plurality of the n protein molecules are conjugated to the substrate using a cleavable linker.
14. The method of claim 1 , wherein at least one of m affinity reagents is modified to be conjugated to an identifiable tag.
15. The method of claim 14 , wherein the identifiable tag comprises a tag selected from the group consisting of: a fluorescent tag, a magnetic tab, a bioluminescent protein tag, a nucleic acid tag, and a nanoparticle.
16. The method of claim 15 , wherein the identifiable tag is a nucleic acid barcode.
17. The method of claim 1 , wherein the number of unique spatial addresses occupied by a protein molecule encoded by a particular gene are counted to quantify the number of protein molecules produced from that particular gene in the sample.
18. The method of claim 1 , wherein the identity of the encoding gene of each of the protein molecules of the plurality of the n protein molecules is determined using a software tool.
19. The method of claim 1 , further comprising determining the encoding gene of each protein molecule of the plurality of the n protein molecules by decoding combinations of epitopes associated with unique spatial addresses.
20. The method of claim 1 , further comprising: denaturing the plurality of the n protein molecules prior to conjugating the plurality of the n protein molecules to the substrate.
21. The method of claim 1 , wherein the protein molecules of the plurality of the n protein molecules conjugated to a substrate are present in a complex mixture of multiple proteins.
22. The method of claim 1 , wherein the method is used to identify multiple proteins.
23. The method of claim 1 , wherein one or more of the m affinity reagents recognize an epitope which comprises a non-contiguous amino acid sequence.
24. The method of claim 1 , wherein the substrate is a flow cell.
25. The method of claim 15 , wherein the identifiable tag is selected from the group consisting of: a fluorescent tag, a magnetic tab, a bioluminescent protein tag, a nucleic acid tag, and a nanoparticle.