| 1. |
- Arndt, Tina, et al.
(författare)
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Engineered Spider Silk Proteins for Biomimetic Spinning of Fibers with Toughness Equal to Dragline Silks
- 2022
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 32:23
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Tidskriftsartikel (refereegranskat)abstract
- Spider silk is the toughest fiber found in nature, and bulk production of artificial spider silk that matches its mechanical properties remains elusive. Development of miniature spider silk proteins (mini-spidroins) has made large-scale fiber production economically feasible, but the fibers’ mechanical properties are inferior to native silk. The spider silk fiber's tensile strength is conferred by poly-alanine stretches that are zipped together by tight side chain packing in β-sheet crystals. Spidroins are secreted so they must be void of long stretches of hydrophobic residues, since such segments get inserted into the endoplasmic reticulum membrane. At the same time, hydrophobic residues have high β-strand propensity and can mediate tight inter-β-sheet interactions, features that are attractive for generation of strong artificial silks. Protein production in prokaryotes can circumvent biological laws that spiders, being eukaryotic organisms, must obey, and the authors thus design mini-spidroins that are predicted to more avidly form stronger β-sheets than the wildtype protein. Biomimetic spinning of the engineered mini-spidroins indeed results in fibers with increased tensile strength and two fiber types display toughness equal to native dragline silks. Bioreactor expression and purification result in a protein yield of ≈9 g L−1 which is in line with requirements for economically feasible bulk scale production.
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| 2. |
- Bombarda, F., et al.
(författare)
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Runaway electron beam control
- 2019
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 61:1
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Bäcklund, Fredrik G., et al.
(författare)
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An Image-Analysis-Based Method for the Prediction of Recombinant Protein Fiber Tensile Strength
- 2022
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 15:3
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Ehrenberg, Angelica, et al.
(författare)
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Accounting for strain variations and resistance mutations in the characterization of hepatitis C NS3 protease inhibitors
- 2014
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Ingår i: Journal of enzyme inhibition and medicinal chemistry (Print). - : Informa UK Limited. - 1475-6366 .- 1475-6374. ; 29:6, s. 868-876
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Tidskriftsartikel (refereegranskat)abstract
- Context: Natural strain variation and rapid resistance development makes development of broad spectrum hepatitis C virus (HCV) drugs very challenging and evaluation of inhibitor selectivity and resistance must account for differences in the catalytic properties of enzyme variants.Objective: To understand how to study selectivity and relationships between efficacy and genotype or resistant mutants for NS3 protease inhibitors.Materials and methods: The catalytic properties of NS3 protease from genotypes 1a, 1b and 3a, and their sensitivities to four structurally and mechanistically different NS3 protease inhibitors have been analysed under different experimental conditions.Results: The optimisation of buffer conditions for each protease variant enabled the comparison of their catalytic properties and sensitivities to the inhibitors. All inhibitors were most effective against genotype 1a protease, with VX-950 having the broadest selectivity.Discussion and conclusion: A new strategy for evaluation of inhibitors relevant for the discovery of broad spectrum HCV drugs was established.
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| 5. |
- Greco, G, et al.
(författare)
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Artificial and natural silk materials have high mechanical property variability regardless of sample size
- 2022
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Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 12:1, s. 3507-
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Tidskriftsartikel (refereegranskat)abstract
- Silk fibres attract great interest in materials science for their biological and mechanical properties. Hitherto, the mechanical properties of the silk fibres have been explored mainly by tensile tests, which provide information on their strength, Young’s modulus, strain at break and toughness modulus. Several hypotheses have been based on these data, but the intrinsic and often overlooked variability of natural and artificial silk fibres makes it challenging to identify trends and correlations. In this work, we determined the mechanical properties of Bombyx mori cocoon and degummed silk, native spider silk, and artificial spider silk, and compared them with classical commercial carbon fibres using large sample sizes (from 10 to 100 fibres, in total 200 specimens per fibre type). The results confirm a substantial variability of the mechanical properties of silk fibres compared to commercial carbon fibres, as the relative standard deviation for strength and strain at break is 10–50%. Moreover, the variability does not decrease significantly when the number of tested fibres is increased, which was surprising considering the low variability frequently reported for silk fibres in the literature. Based on this, we prove that tensile testing of 10 fibres per type is representative of a silk fibre population. Finally, we show that the ideal shape of the stress–strain curve for spider silk, characterized by a pronounced exponential stiffening regime, occurs in only 25% of all tested spider silk fibres.
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| 6. |
- Greco, Gabriele, et al.
(författare)
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Influence of experimental methods on the mechanical properties of silk fibers: A systematic literature review and future road map
- 2023
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Ingår i: Biophysics reviews. - 2688-4089. ; 4
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Forskningsöversikt (refereegranskat)abstract
- Spider silk fibers are of scientific and industrial interest because of their extraordinary mechanical properties. These properties are normally determined by tensile tests, but the values obtained are dependent on the morphology of the fibers, the test conditions, and the methods by which stress and strain are calculated. Because of this, results from many studies are not directly comparable, which has led to widespread misconceptions in the field. Here, we critically review most of the reports from the past 50 years on spider silk mechanical performance and use artificial spider silk and native silks as models to highlight the effect that different experimental setups have on the fibers' mechanical properties. The results clearly illustrate the importance of carefully evaluating the tensile test methods when comparing the results from different studies. Finally, we suggest a protocol for how to perform tensile tests on silk and biobased fibers.
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| 7. |
- Greco, Gabriele, et al.
(författare)
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Properties of Biomimetic Artificial Spider Silk Fibers Tuned by PostSpin Bath Incubation
- 2020
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Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 25:14
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Tidskriftsartikel (refereegranskat)abstract
- Efficient production of artificial spider silk fibers with properties that match its natural counterpart has still not been achieved. Recently, a biomimetic process for spinning recombinant spider silk proteins (spidroins) was presented, in which important molecular mechanisms involved in native spider silk spinning were recapitulated. However, drawbacks of these fibers included inferior mechanical properties and problems with low resistance to aqueous environments. In this work, we show that >= 5 h incubation of the fibers, in a collection bath of 500 mM NaAc and 200 mM NaCl, at pH 5 results in fibers that do not dissolve in water or phosphate buffered saline, which implies that the fibers can be used for applications that involve wet/humid conditions. Furthermore, incubation in the collection bath improved the strain at break and was associated with increased beta-sheet content, but did not affect the fiber morphology. In summary, we present a simple way to improve artificial spider silk fiber strain at break and resistance to aqueous solvents.
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| 8. |
- Greco, Gabriele, et al.
(författare)
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Tyrosine residues mediate supercontraction in biomimetic spider silk
- 2021
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Ingår i: Communications materials. - : Springer Science and Business Media LLC. - 2662-4443. ; 2:1
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Tidskriftsartikel (refereegranskat)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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| 9. |
- Jafari, Mohammad Javad, et al.
(författare)
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Force-Induced Structural Changes in Spider Silk Fibers Introduced by ATR-FTIR Spectroscopy
- 2023
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Ingår i: ACS applied polymer materials. - : American Chemical Society. - 2637-6105. ; 5:11, s. 9433-9444
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Tidskriftsartikel (refereegranskat)abstract
- Silk fibers have unique mechanical properties, and many studies of silk aim at understanding how these properties are related to secondary structure content, which often is determined by infrared spectroscopy. We report significant method-induced irreversible structural changes to both natural and synthetic spider silk fibers, derived from the widely used attenuated total reflection Fourier-transform infrared (ATR-FTIR) technique. By varying the force used to bring fibers into contact with the internal reflection elements of ATR-FTIR accessories, we observed correlated and largely irreversible changes in the secondary structure, with shape relaxation under pressure occurring within minutes. Fitting of spectral components shows that these changes agree with transformations from the alpha-helix to the beta-sheet secondary structure with possible contributions from other secondary structure elements. We further confirm the findings with IR microspectroscopy, where similar differences were seen between the pressed and unaffected regions of spider silk fibers. Our findings show that ATR-FTIR spectroscopy requires care in its use and in the interpretation of the results.
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| 10. |
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