| 1. |
- Bäcklund, Fredrik G., et al.
(author)
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An Image-Analysis-Based Method for the Prediction of Recombinant Protein Fiber Tensile Strength
- 2022
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In: Materials. - : MDPI AG. - 1996-1944. ; 15:3
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Journal article (peer-reviewed)abstract
- Silk fibers derived from the cocoon of silk moths and the wide range of silks produced by spiders exhibit an array of features, such as extraordinary tensile strength, elasticity, and adhesive properties. The functional features and mechanical properties can be derived from the structural composition and organization of the silk fibers. Artificial recombinant protein fibers based on engineered spider silk proteins have been successfully made previously and represent a promising way towards the large-scale production of fibers with predesigned features. However, for the production and use of protein fibers, there is a need for reliable objective quality control procedures that could be automated and that do not destroy the fibers in the process. Furthermore, there is still a lack of understanding the specifics of how the structural composition and organization relate to the ultimate function of silk-like fibers. In this study, we develop a new method for the categorization of protein fibers that enabled a highly accurate prediction of fiber tensile strength. Based on the use of a common light microscope equipped with polarizers together with image analysis for the precise determination of fiber morphology and optical properties, this represents an easy-to-use, objective non-destructive quality control process for protein fiber manufacturing and provides further insights into the link between the supramolecular organization and mechanical functionality of protein fibers.
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| 2. |
- Bäcklund, Fredrik G., et al.
(author)
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Controlling Amyloid Fibril Formation by Partial Stirring
- 2016
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In: Biopolymers. - : Wiley-Blackwell. - 0006-3525 .- 1097-0282. ; 105:5, s. 249-259
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Journal article (peer-reviewed)abstract
- Many proteins undergoes self-assembly into fibrillar structures known as amyloid fibrils. During the self-assembly process related structures, known as spherulites, can be formed. Herein we report a facile method where the balance between amyloid fibrils and spherulites can be controlled by stirring of the reaction mixture during the initial stages of the self-assembly process. Moreover, we report how this methodology can be used to prepare non-covalently functionalized amyloid fibrils. By stirring the reaction mixture continuously or for a limited time during the lag phase the fibril length, and hence the propensity to form liquid crystalline phases, can be influenced. This phenomena is utilized by preparing films consisting of aligned protein fibrils incorporating the laser dye Nile red. The resulting films display polarized Nile red fluorescence.
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| 3. |
- Bäcklund, Fredrik G., et al.
(author)
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Tuning the aqueous self-assembly process of insulin by a hydrophobic additive
- 2015
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In: RSC ADVANCES. - : Royal Society of Chemistry. - 2046-2069. ; 5:112, s. 92254-92262
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Journal article (peer-reviewed)abstract
- Biomolecular self-assembly is an efficient way of preparing soft-matter based materials. Herein we report a novel method, based on the use of insoluble additives in aqueous media, for influencing the self-assembly process. Due to their low solubility, the use of hydrophobic additives in aqueous media is problematic; however, by mixing the additive with the biomolecule in the solid state, prior to solvation, this problem can be circumvented. In the investigated self-assembly system, where bovine insulin self-assembles into spherical structures, the inclusion of the hydrophobic material α-sexithiophene (6T) results in significant changes in the self-assembly process. Under our reaction conditions, in the case of materials prepared from insulin-only the growth of spherulites typically stops at a diameter of 150μm. However, by adding 2 weight % of hydrophobic material, spherulite growth continues up to diameters in the mm-range. The spherulites incorporate 6T and are thus fluorescent. The method reported herein should be of interest to all scientists working in the field of self-assembly as the flexible materials preparation, based simply on co-grinding of commercially available materials, adds another option to influence the structure and properties of products formed by self-assembly reactions.
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| 4. |
- Greco, Gabriele, et al.
(author)
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Tyrosine residues mediate supercontraction in biomimetic spider silk
- 2021
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In: Communications materials. - : Springer Science and Business Media LLC. - 2662-4443. ; 2:1
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Journal article (peer-reviewed)abstract
- Exposing spider silk to wet conditions can cause supercontraction. Here, tyrosine amino acid residues within the amorphous regions are found to contribute to supercontraction, which can be controlled by protein engineering. Water and humidity severely affect the material properties of spider major ampullate silk, causing the fiber to become plasticized, contract, swell and undergo torsion. Several amino acid residue types have been proposed to be involved in this process, but the complex composition of the native fiber complicates detailed investigations. Here, we observe supercontraction in biomimetically produced artificial spider silk fibers composed of defined proteins. We found experimental evidence that proline is not the sole residue responsible for supercontraction and that tyrosine residues in the amorphous regions of the silk fiber play an important role. Furthermore, we show that the response of artificial silk fibers to humidity can be tuned, which is important for the development of materials for applications in wet environments, eg producing water resistant fibers with maximal strain at break and toughness modulus.
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