Protein sequencing via coupling of polymerizable molecules
Provided herein are methods and systems for sequencing proteins. One or more methods disclosed herein may use linkers having an amino acid-reactive group and an additional reactive moiety that may be used to couple a polymerizable molecule. The linker may couple to a polymerizable molecule and an amino acid of a peptide and a capture moiety via the polymerizable molecule, followed by cleavage of the amino acid from the peptide. Further processing and analysis may be conducted using, for example, nanopores or nanogaps.
1. A method of identifying a modified amino acid, comprising:
(a) providing a peptide, wherein said peptide comprises a plurality of amino acids;
(b) coupling a linker comprising a polymerizable molecule to an amino acid of said plurality of amino acids, thereby yielding an amino acid-linker complex;
(c) cleaving said amino acid-linker complex from said peptide, thereby yielding said modified amino acid;
(d) measuring a signal of said modified amino acid while said modified amino acid translocates through a nanopore or a nanogap, thereby generating a measured signal;
(e) using said measured signal to identify an amino acid type of said modified amino acid.
2. The method of claim 1 , wherein said cleaving is performed using a chemical stimulus.
3. The method of claim 2 , wherein said chemical stimulus comprises application of an acid.
4. The method of claim 3 , wherein said acid is a Lewis acid.
5. The method of claim 1 , further comprising, repeating (b)-(e), thereby sequencing said peptide.
6. The method of claim 1 , wherein (b) comprises (i) providing said linker comprising said polymerizable molecule, wherein said linker comprises an amino acid reactive moiety; and (ii) reacting said amino acid reactive moiety with said amino acid, thereby generating said amino acid-linker complex.
7. The method of claim 6 , wherein said amino acid reactive moiety is an isothiocyanate, a thioacetylation agent, a thioacylation agent, a thiobenzoylation agent, or a guanidinylating agent.
8. The method of claim 6 , further comprising, subsequent to (c), repeating (b), thereby generating an additional amino acid-linker complex from an additional amino acid of said plurality of amino acids.
9. The method of claim 8 , further comprising, coupling said additional amino acid-linker complex to said amino-acid linker complex such that a distance between said amino acid and said additional amino acid is increased, and subsequently, cleaving said additional amino acid-linker complex from said peptide.
10. The method of claim 8 , wherein said polymerizable molecule comprises temporal information, wherein said temporal information comprises a cycle or round that said polymerizable molecule is provided.
11. The method of claim 6 , wherein said peptide is coupled to a capture moiety, and wherein (b) further comprises, coupling said capture moiety to said linker.
12. The method of claim 11 , wherein said coupling is mediated via said polymerizable molecule.
13. The method of claim 11 , wherein said capture moiety comprises a nucleic acid barcode molecule.
14. The method of claim 13 , wherein said nucleic acid barcode molecule identifies said peptide.
15. The method of claim 13 , wherein said capture moiety comprises a unique molecular identifier (UMI) sequence.
16. The method of claim 1 , wherein said polymerizable molecule comprises a nucleic acid molecule.
17. The method of claim 16 , wherein said nucleic acid molecule is composed predominantly of pyrimidines.
18. The method of claim 17 , wherein said nucleic acid molecule is composed entirely of pyrimidines.
19. The method of claim 16 , wherein said nucleic acid molecule comprises a polynucleotide analog.
20. The method of claim 19 , wherein said polynucleotide analog comprises a 7-deaza purine analog, 8-halopurine analog, or 5-halopyrimidine analog.
21. The method of claim 1 , wherein said modified amino acid comprises a post-translational modification and wherein (e) comprises identifying said post-translational modification.
22. The method of claim 1 , wherein said peptide is derived from a biological sample.
23. The method of claim 1 , wherein said amino acid is a terminal amino acid.
24. The method of claim 1 , wherein said measured signal is a current signal.
25. The method of claim 1 , wherein said modified amino acid comprises a thiocarbamyl, thiazolinone or thiohydantoin-derivatized amino acid.
26. The method of claim 1 , wherein said polymerizable molecule comprises temporal information or spatial information.
27. The method of claim 1 , wherein during (a), said peptide is coupled to a substrate.
28. The method of claim 1 , wherein said polymerizable molecule comprises a nucleic acid molecule, and further comprising, using said nanopore or said nanogap to sequence said nucleic acid molecule.
29. The method of claim 1 , further comprising, translocating said modified amino acid through said nanopore or said nanogap more than once.
30. The method of claim 1 , wherein said polymerizable molecule comprises a synthetic polymer.