Decoding approaches for protein identification
Methods and systems are provided for accurate and efficient identification and quantification of proteins. In an aspect, disclosed herein is a method for identifying a protein in a sample of unknown proteins, comprising receiving information of a plurality of empirical measurements performed on the unknown proteins; comparing the information of empirical measurements against a database comprising a plurality of protein sequences, each protein sequence corresponding to a candidate protein among a plurality of candidate proteins; and for each of one or more of the plurality of candidate proteins, generating a probability that the candidate protein generates the information of empirical measurements, a probability that the plurality of empirical measurements is not observed given that the candidate protein is present in the sample, or a probability that the candidate protein is present in the sample; based on the comparison of the information of empirical measurements against the database.
1. A method for identifying proteins in a sample and their position on a substrate, comprising:
providing a plurality of proteins attached to a substrate;
carrying out a series of affinity binding measurements by exposing the plurality of proteins attached to unique spatial addresses on the substrate to a series of tagged affinity reagents to produce an outcome set comprising positive binding outcomes and negative binding outcomes for the plurality of proteins with the tagged affinity reagents;
providing a database comprising a set of candidate proteins, and calculating for each candidate protein, a probability of observing a positive binding outcome or negative binding outcome with each of the tagged affinity reagents;
identifying the plurality of proteins attached to the substrate by determining with a computer, using the database, calculated probability, and the outcome set, a most probable candidate protein or most probable group of candidate proteins in the database corresponding to each of the proteins attached to the substrate; and
storing the identification of each protein in the plurality of proteins and its corresponding unique spatial address on the substrate to a computer memory to identify the proteins present in the sample.
2. The method of claim 1 , wherein the plurality of proteins comprises at least 1000 unknown proteins.
3. The method of claim 1 , wherein the set of candidate proteins comprises at least 500 different candidate proteins.
4. The method of claim 1 , wherein the series of tagged affinity reagents comprise at least 200 tagged affinity reagents.
5. The method of claim 1 , wherein the tagged affinity reagents have at least 4 off-target binding sites in the set of candidate proteins.
6. The method of claim 5 , wherein the off-target binding sites comprise biosimilar off-target binding sites.
7. The method of claim 5 , wherein the off-target binding sites comprise random off-target binding sites.
8. The method of claim 1 , wherein the tagged affinity reagents have fewer than 99 off-target binding sites in the set of candidate proteins.
9. The method of claim 1 , wherein the tagged affinity reagents recognize multiple epitopes.
10. The method of claim 1 , wherein the tagged affinity reagents recognize at least 5 amino acid trimers.
11. The method of claim 1 , wherein the determining step also uses empirical measurements including one or more of the length, the hydrophobicity, or the isoelectric point of one or more of said proteins attached to the substrate.
12. The method of claim 1 , wherein the series of tagged affinity reagents comprise antibodies.
13. The method of claim 1 , wherein the series of tagged affinity reagents comprise fluorescent tags.
14. The method of claim 1 , wherein the series of tagged affinity reagents comprises 100 or more tagged affinity reagents, each of the tagged affinity reagents binding to a different protein.
15. The method of claim 1 , wherein the tagged affinity reagents each recognizes 10-40 amino acid trimers.
16. The method of claim 1 , wherein the tagged affinity reagents each recognizes 5-60 amino acid trimers.
17. The method of claim 1 , wherein the series of tagged affinity reagents comprise N t tagged affinity reagents, and wherein target binding sites of the tagged affinity reagents correspond to the top N t most abundant amino acid trimers among the set of candidate proteins.
18. The method of claim 1 , wherein target binding sites of the tagged affinity reagents were randomly selected from the amino acid trimers present in the set of candidate proteins.
19. A method for identifying proteins in a sample and their position on a substrate comprising:
providing at least 1000 proteins attached to unique spatial addresses on a substrate;
carrying out a series of affinity binding measurements by exposing the at least 1000 proteins attached to the substrate to a series of tagged affinity reagents to produce an outcome set comprising positive binding outcomes and negative binding outcomes for the at least 1000 proteins with the tagged affinity reagents, wherein each of the tagged affinity reagents recognizes at least 5 amino acid trimers;
providing a database comprising a set of candidate proteins, and calculating for each candidate protein, a probability of observing a positive binding outcome or negative binding with each of the tagged affinity reagents;
identifying the at least 1000 proteins attached to the substrate by determining with a computer, using the database, the calculated probability, and the outcome set, a most probable candidate protein or most probable group of candidate proteins in the database corresponding to the proteins attached to the substrate; and
storing the identification of each protein in the at least 1000 proteins and its corresponding unique spatial address on the substrate to a computer memory to identify the proteins present in the sample.
20. The method of claim 19 , wherein the set of candidate proteins comprises at least 500 different candidate proteins.
21. The method of claim 19 , wherein the series of tagged affinity reagents comprise at least 200 tagged affinity reagents.
22. The method of claim 19 , wherein the tagged affinity reagents have at least 4 off-target binding sites.
23. The method of claim 22 , wherein the off-target binding sites comprise biosimilar off-target binding sites.
24. The method of claim 22 , wherein the off-target binding sites comprise random off-target binding sites in the set of candidate proteins.
25. The method of claim 19 , wherein the tagged affinity reagents have fewer than 99 off-target binding sites in the set of candidate proteins.
26. The method of claim 19 , wherein the determining step also uses empirical measurements including one or more of the length, the hydrophobicity, or the isoelectric point of one or more of said proteins attached to the substrate.
27. The method of claim 19 , wherein the series of tagged affinity reagents comprise tagged antibodies.
28. The method of claim 19 , wherein the series of tagged affinity reagents comprise fluorescent tags.
29. The method of claim 19 , wherein the series of tagged affinity reagents comprise 100 or more tagged affinity reagents.
30. The method of claim 19 , wherein the tagged affinity reagents each recognizes 10-40 amino acid trimers.
31. The method of claim 19 , wherein the tagged affinity reagents each recognizes 5-60 amino acid trimers.
32. The method of claim 19 , wherein the series of tagged affinity reagents comprise N t tagged affinity reagents, and wherein target binding sites of the tagged affinity reagents correspond to the top N t most abundant amino acid trimers among the set of candidate proteins.
33. The method of claim 19 , wherein target binding sites of the tagged affinity reagents were randomly selected from the amino acid trimers present in the set of candidate proteins.