α-helical protein based materials and methods for making same
The invention relates to a method of producing useful materials from filament-forming α-helical proteins or filaments made of such proteins. The method comprises allowing filament-forming α-helical proteins to self-assemble into α-helix containing filaments and forming fibres, films or bulk materials from the filaments. The materials are stretched to strain the filaments so that the α-helices substantially irreversibly change to β-sheet forms. The filament-forming α-helical proteins can comprise intermediate filament proteins. In a specific embodiment, the filament-forming proteins comprise hagfish slime thread IF proteins.
1. A method of making protein filament based materials, the method comprising:
obtaining α-helix containing filaments of filament-forming α-helical proteins; and,
stretching at least some of the α-helix containing filaments sufficiently to alter the structure of the at least some of the α-helix containing filaments from an α-helical structure to a β-sheet structure;
wherein the α-helix containing filaments comprise intermediate filaments substantially free of a protein matrix, and wherein the altered filaments substantially retain the β-sheet structure after the stretching.
2. A method according to claim 1 , comprising forming the α-helix containing filaments into a larger structure wherein stretching at least some of the α-helix containing filaments comprises stretching the larger structure.
3. A method according to claim 2 , wherein stretching the at least some of the α-helix containing filaments occurs substantially simultaneously with formation of the larger structure.
4. A method according to claim 2 , wherein the larger structure comprises a fibre, film, or a bulk material.
5. A method according to claim 1 , wherein a majority of the α-helix containing filaments are aligned in one or more preferred directions.
6. A method according to claim 5 , wherein the α-helix containing filaments are aligned by adding an alignment-promoting material selected from the group consisting of a cytolinker protein, filaggrin, homerin, and plakin.
7. A method according to claim 5 , wherein the α-helix containing filaments are aligned by altering pH, ionic strength, or composition of a buffer containing the α-helix containing filaments.
8. A method according to claim 5 , wherein the α-helix containing filaments are aligned by flow, by charge, or by substrate directed alignment.
9. A method according to claim 1 , wherein obtaining α-helix containing filaments comprises obtaining the filament-forming α-helical proteins and forming the α-helix containing filaments from the filament-forming α-helical proteins.
10. A method according to claim 9 , wherein forming the α-helix containing filaments from the filament-forming α-helical proteins comprises providing conditions suitable for causing the filament-forming α-helical proteins to self-assemble into the α-helix containing filaments.
11. A method according to claim 1 , wherein the α-helix containing filaments have diameters in the range of 1 nm to 16 nm.
12. A method according to claim 1 , wherein the α-helix containing filaments have lengths in the range of 100 nm to 100 μm.
13. A method according to claim 12 , wherein the α-helix containing filaments have lengths in the range of 5 μm to 30 μm.
14. A method according to claim 1 , wherein the intermediate filaments have diameters in the range of 7 nm to 16 nm.
15. A method according to claim 14 , wherein the intermediate filaments are made up of filament-forming α-helical proteins having weights not exceeding 100 kDa.
16. A method according to claim 15 , wherein the intermediate filaments comprise one or more proteins having a weight of approximately 67 kDa.
17. A method according to claim 1 , wherein the α-helix containing filaments comprise hagfish slime threads.
18. A method according to claim 17 , wherein the hagfish slime threads are derived from Eptatretus stoutii.
19. A method according to claim 1 , wherein stretching the at least some of the α-helix containing filaments comprises repeatedly applying to and removing from the at least some of the α-helix containing filaments a load sufficient to alter a structure of the at least some of the α-helix containing filaments.
20. A method according to claim 19 , comprising drying the at least some of the α-helix containing filaments before stretching the at least some of the α-helix containing filaments.
21. A method according to claim 20 , wherein stretching the at least some of the α-helix containing filaments comprises extending the α-helix containing filaments to a strain in excess of ε=0.025.
22. A method according to claim 21 , wherein stretching the at least some of the α-helix containing filaments comprises extending the α-helix containing filaments to a strain not exceeding about ε=1.0.
23. A method according to claim 19 , comprising stretching the at least some of the α-helix containing filaments when the at least some of the α-helix containing filaments are wet.
24. A method according to claim 23 , wherein stretching the at least some of the α-helix containing filaments is performed in the presence of one or more of: one or more aqueous solvents; one or more non-aqueous solvents; and one or more plasticizers.
25. A method according to claim 23 , wherein stretching the at least some of the α-helix containing filaments comprises extending the α-helix containing filaments to a strain of at least about ε=0.35.
26. A method according to claim 25 wherein stretching the at least some of the α-helix containing filaments comprises extending the α-helix containing filaments to a strain not exceeding about ε=2.2.
27. A method according to claim 1 , wherein obtaining the α-helix containing filaments comprises concentrating the α-helix containing filaments to a concentration of at least 0.5 mg/ml.
28. A method according to claim 27 wherein obtaining the α-helix containing filaments comprises concentrating the α-helix containing filaments to a concentration in the range of 0.5 mg/ml to 100 mg/ml.
29. A method according to claim 27 , wherein concentrating the α-helix containing filaments is performed in an aqueous solution.
30. A method according to claim 1 , comprising promoting cross-linking between proteins of the α-helix containing filaments.
31. A method according to claim 30 , wherein promoting cross-linking between proteins of the α-helix containing filaments is performed before stretching at least some of the α-helix containing filaments.
32. A method according to claim 30 , wherein promoting cross-linking between proteins of the α-helix containing filaments is performed after stretching at least some of the α-helix containing filaments.
33. A method according to claim 1 , comprising plasticizing the at least some of the α-helix containing filaments.
34. A method according to claim 33 , wherein plasticizing the at least some of the α-helix containing filaments is performed before stretching the at least some of the α-helix containing filaments.
35. A method according to claim 33 , wherein plasticizing the at least some of the α-helix containing filaments is performed after stretching the at least some of the α-helix containing filaments.
36. A method according to claim 1 , wherein the α-helix containing filaments comprise recombinant proteins.
37. A method according to claim 1 , wherein obtaining the filament-forming α-helical proteins comprises expressing the filament-forming α-helical proteins in a cell free translation system.
38. A method according to claim 1 , wherein obtaining the filament-forming α-helical proteins comprises synthesizing the filament-forming α-helical proteins by chemical peptide synthesis.