1
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Evolution of conformation and thermal properties of bovine hides collagen in the sodium sulphide solution. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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2
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Asakura T, Matsuda H, Aoki A, Naito A. Acetylation and hydration treatment of recombinant spider silk fiber, and their characterization using 13C NMR spectroscopy. POLYMER 2022. [DOI: 10.1016/j.polymer.2022.124605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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3
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Yazawa K, Tatebayashi Y, Kajiura Z. Eri silkworm spins mechanically robust silk fibers regardless of reeling speed. J Exp Biol 2022; 225:274025. [PMID: 35037048 DOI: 10.1242/jeb.243458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Accepted: 01/07/2022] [Indexed: 11/20/2022]
Abstract
Wild silkworms survive in the environmental habitats in which temperature and humidity vary based on weather. In contrast, domesticated silkworms live in mild environments where temperature and humidity are generally maintained at constant levels. Previous studies showed that the mechanical strengths and molecular orientation of the silk fibers reeled from domesticated silkworms are significantly influenced by the reeling speed. Here we investigated the effects of the reeling speeds on the mechanical properties of eri silk fibers produced by wild silkworms, Samia cynthia ricini, which belong to the family of Saturniidae. We found that the structural, morphological, and mechanical features of eri silk fibers are maintained irrespective of the reeling speed in contrast to those of domesticated silkworm silk fibers. The obtained results are useful not only for understanding the biological basis underlying the natural formation of silk fibers but also for contributing to the design of artificial spinning systems for producing synthetic silk fibers.
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Affiliation(s)
- Kenjiro Yazawa
- Department of Applied Biology, Faculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda City, Nagano 386-8567, Japan.,Division of Biological and Medical Fiber, Institute for Fiber Engineering, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, 3-15-1 Tokida, Ueda City, Nagano 386-8567, Japan
| | - Yuka Tatebayashi
- Department of Applied Biology, Faculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda City, Nagano 386-8567, Japan
| | - Zenta Kajiura
- Department of Applied Biology, Faculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda City, Nagano 386-8567, Japan
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4
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Mohammadi P, Zemke F, Wagermaier W, Linder MB. Interfacial Crystallization and Supramolecular Self-Assembly of Spider Silk Inspired Protein at the Water-Air Interface. MATERIALS (BASEL, SWITZERLAND) 2021; 14:4239. [PMID: 34361434 PMCID: PMC8348448 DOI: 10.3390/ma14154239] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 07/26/2021] [Accepted: 07/27/2021] [Indexed: 11/21/2022]
Abstract
Macromolecular assembly into complex morphologies and architectural shapes is an area of fundamental research and technological innovation. In this work, we investigate the self-assembly process of recombinantly produced protein inspired by spider silk (spidroin). To elucidate the first steps of the assembly process, we examined highly concentrated and viscous pendant droplets of this protein in air. We show how the protein self-assembles and crystallizes at the water-air interface into a relatively thick and highly elastic skin. Using time-resolved in situ synchrotron x-ray scattering measurements during the drying process, we showed that the skin evolved to contain a high β-sheet amount over time. We also found that β-sheet formation strongly depended on protein concentration and relative humidity. These had a strong influence not only on the amount, but also on the ordering of these structures during the β-sheet formation process. We also showed how the skin around pendant droplets can serve as a reservoir for attaining liquid-liquid phase separation and coacervation from the dilute protein solution. Essentially, this study shows a new assembly route which could be optimized for the synthesis of new materials from a dilute protein solution and determine the properties of the final products.
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Affiliation(s)
- Pezhman Mohammadi
- VTT Technical Research Centre of Finland Ltd., FI-02044 Espoo, Finland
| | - Fabian Zemke
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany; (F.Z.); (W.W.)
| | - Wolfgang Wagermaier
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany; (F.Z.); (W.W.)
| | - Markus B. Linder
- Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, FI-02150 Espoo, Finland;
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5
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Hu CF, Qian ZG, Peng Q, Zhang Y, Xia XX. Unconventional Spidroin Assemblies in Aqueous Dope for Spinning into Tough Synthetic Fibers. ACS Biomater Sci Eng 2021; 7:3608-3617. [PMID: 34259496 DOI: 10.1021/acsbiomaterials.1c00492] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Spider dragline silk is a remarkable fiber made by spiders from an aqueous solution of spidroins, and this feat is largely attributed to the tripartite domain architecture of the silk proteins leading to the hierarchical assembly at the nano- and microscales. Although individual amino- and carboxy-terminal domains have been proposed to relate to silk protein assembly, their tentative synergizing roles in recombinant spidroin storage and spinning into synthetic fibers remain elusive. Here, we show biosynthesis and self-assembly of a mimic spidroin composed of amino- and carboxy-terminal domains bracketing 16 consensus repeats of the core region from spider Trichonephila clavipes. The presence of both termini was found essential for self-assembly of the mimic spidroin termed N16C into fibril-like (rather than canonical micellar) nanostructures in concentrated aqueous dope and ordered alignment of these nanofibrils upon extrusion into an acidic coagulation bath. This ultimately led to continuous, macroscopic fibers with a tensile fracture toughness of 100.9 ± 13.2 MJ m-3, which is comparable to that of their natural counterparts. We also found that the recombinant proteins lacking one or both termini were unable to similarly preassemble into fibrillar nanostructures in dopes and thus yielded inferior fiber properties. This work thereby highlights the synergizing role of terminal domains in the storage and processing of recombinant analogues into tough synthetic fibers.
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Affiliation(s)
- Chun-Fei Hu
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Zhi-Gang Qian
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Qingfa Peng
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Yaopeng Zhang
- State Key Laboratory for Modification of Chemical Fibres and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, People's Republic of China
| | - Xiao-Xia Xia
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
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6
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Forcibly spun dragline silk fibers from web-building spider Trichonephila clavata ensure robustness irrespective of spinning speed and humidity. Int J Biol Macromol 2020; 168:550-557. [PMID: 33333091 DOI: 10.1016/j.ijbiomac.2020.12.076] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 12/01/2020] [Accepted: 12/10/2020] [Indexed: 12/20/2022]
Abstract
Web-building spiders secrete dragline silk fibers to sustain their body and use them as frameworks during web construction. They spin dragline silk fibers at various spinning speed and humidity conditions depending on their natural habitat. Here, we investigated the effect of spinning speed and humidity on the structural and mechanical properties of dragline silk fibers from web-building spider Trichonephila clavata obtained by the forcibly spinning method. We found that the crystal and morphological structures did not rely on the spinning speed and humidity. Furthermore, the mechanical strength and extensibility of the dragline silk fibers were maintained, demonstrating that dragline silk fibers ensure robustness irrespective of the spinning speed and humidity. The results obtained in the present study are helpful not only to understand the biological basis of the silk fiber formation of spiders but also contribute to consider the spinning conditions for the process of creating synthetic silk fibers.
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7
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Asakura T. Structure and Dynamics of Spider Silk Studied with Solid-State Nuclear Magnetic Resonance and Molecular Dynamics Simulation. Molecules 2020; 25:E2634. [PMID: 32517041 PMCID: PMC7321385 DOI: 10.3390/molecules25112634] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 06/01/2020] [Accepted: 06/01/2020] [Indexed: 01/01/2023] Open
Abstract
This review will introduce very recent studies using solid-state nuclear magnetic resonance (NMR) and molecular dynamics (MD) simulation on the structure and dynamics of spider dragline silks conducted by the author's research group. Spider dragline silks possess extraordinary mechanical properties by combining high tensile strength with outstanding elongation before breaking, and therefore continue to attract attention of researchers in biology, biochemistry, biophysics, analytical chemistry, polymer technology, textile technology, and tissue engineering. However, the inherently non-crystalline structure means that X-ray diffraction and electron diffraction methods provide only limited information because it is difficult to study the molecular structure of the amorphous region. The most detailed picture of the structure and dynamics of the silks in the solid state experimentally have come from solid-state NMR measurements coupled with stable isotope labeling of the silks and the related silk peptides. In addition, combination of solid-state NMR and MD simulation was very powerful analytical tools to understand the local conformation and dynamics of the spider dragline silk in atomic resolution. In this review, the author will emphasize how solid-state NMR and MD simulation have contributed to a better understanding of the structure and dynamics in the spider dragline silks.
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Affiliation(s)
- Tetsuo Asakura
- Department of Biotechnology, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588, Japan
- Department of Biotechnology, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588, Japan
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8
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Wang Z, Cang Y, Kremer F, Thomas EL, Fytas G. Determination of the Complete Elasticity of Nephila pilipes Spider Silk. Biomacromolecules 2020; 21:1179-1185. [PMID: 31935074 PMCID: PMC7307882 DOI: 10.1021/acs.biomac.9b01607] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
![]()
Spider silks are
remarkable materials designed by nature to have
extraordinary elasticity. Their elasticity, however, remains poorly
understood, as typical stress–strain experiments only allow
access to the axial Young’s modulus. In this work, micro-Brillouin
light spectroscopy (micro-BLS), a noncontact, nondestructive technique,
is utilized to probe the direction-dependent phonon propagation in
the Nephila pilipes spider silk and
hence solve its full elasticity. To the best of our knowledge, this
is the first demonstration on the determination of the anisotropic
Young’s moduli, shear moduli, and Poisson’s ratios of
a single spider fiber. The axial and lateral Young’s moduli
are found to be 20.9 ± 0.8 and 9.2 ± 0.3 GPa, respectively,
and the anisotropy of the Young’s moduli further increases
upon stretching. In contrast, the shear moduli and Poisson’s
ratios exhibit very weak anisotropy and are robust to stretching.
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Affiliation(s)
- Zuyuan Wang
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Yu Cang
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Friedrich Kremer
- Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, 04103 Leipzig, Germany
| | - Edwin L Thomas
- Department of Materials Science and Nano-Engineering, Rice University, Houston, Texas 77030, United States
| | - George Fytas
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.,Institute of Electronic Structure and Laser, F.O.R.T.H, 70013 Heraklion, Greece
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9
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Asakura T, Okonogi M, Naito A. Toward Understanding the Silk Fiber Structure: 13C Solid-State NMR Studies of the Packing Structures of Alanine Oligomers before and after Trifluoroacetic Acid Treatment. J Phys Chem B 2019; 123:6716-6727. [PMID: 31304756 DOI: 10.1021/acs.jpcb.9b04565] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Polyalanine (poly-A) sequences with tightly packed antiparallel β sheet (AP-β) structures are frequently observed in silk fibers and serve as a key contributor to the exceptionally high-fiber tensile strength. In general, the poly-A sequence embedded in the amorphous glycine-rich regions has different lengths depending on the fiber type from spiders or wild silkworms. In this paper, the packing structures of AP-β alanine oligomers with different lengths were studied using 13C solid-state NMR as a model of the poly-A sequences. These included alanine oligomers with and without the protection groups (i.e., 9-fluorenylmethoxycarbonyl and polyethylene glycol groups at the N- and C-terminals, respectively). The fractions of the packing structures as well as the conformations were determined by deconvolution analyses of the methyl NMR peaks. Trifluoroacetic acid was used to promote the staggered packing structures, and the line shapes changed significantly for oligomers without the protected groups but only slightly for oligomers with the protected groups. Through NMR analysis of the 3-13C singly labeled alanine heptamer and refined crystal structure of the staggered packing units, a possible mechanism of the staggered packing formation is proposed for the AP-β alanine heptamer.
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Affiliation(s)
- Tetsuo Asakura
- Department of Biotechnology , Tokyo University of Agriculture and Technology , Koganei , Tokyo 184-8588 , Japan
| | - Michi Okonogi
- Department of Biotechnology , Tokyo University of Agriculture and Technology , Koganei , Tokyo 184-8588 , Japan
| | - Akira Naito
- Department of Biotechnology , Tokyo University of Agriculture and Technology , Koganei , Tokyo 184-8588 , Japan
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10
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Niu Q, Peng Q, Lu L, Fan S, Shao H, Zhang H, Wu R, Hsiao BS, Zhang Y. Single Molecular Layer of Silk Nanoribbon as Potential Basic Building Block of Silk Materials. ACS NANO 2018; 12:11860-11870. [PMID: 30407791 DOI: 10.1021/acsnano.8b03943] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In this study, nascent silk nanoribbons (SNRs) with an average thickness of 0.4 nm were extracted from natural silkworm silk by partially dissolving degummed silk (DS) in sodium hydroxide (NaOH)/urea solution at -12 °C. In this gentle treatment, the solvent could not destroy the nanofibrillar structure completely, but the chosen conditions would influence the dimensions of resulting SNRs. Molecular dynamics simulations of silk models indicated that the potential of mean force required to break hydrogen bonds between silk fibroin chains was 40% larger than that of van der Waals interactions between β-sheet layers, allowing the exfoliating treatment. It was found that the resulting SNRs contained a single β-sheet layer and amorphous silk fibroin molecules, which could be considered as the basic building block of DS consisting of hierarchical structures. The demonstrated technique for extracting ultrathin SNRs having the height of a single β-sheet layer may provide a useful pathway for creating stronger and tougher silk-based materials and/or adding functionality and durability in materials for various applications. The hierarchical structure model based on SNRs may afford more insight into the structure and property relationship of fabricating silk-based materials.
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Affiliation(s)
- Qianqian Niu
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, International Joint Laboratory for Advanced Fiber and Low-Dimension Materials , College of Materials Science and Engineering, Donghua University , Shanghai , 201620 , China
| | - Qingfa Peng
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, International Joint Laboratory for Advanced Fiber and Low-Dimension Materials , College of Materials Science and Engineering, Donghua University , Shanghai , 201620 , China
| | - Li Lu
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, International Joint Laboratory for Advanced Fiber and Low-Dimension Materials , College of Materials Science and Engineering, Donghua University , Shanghai , 201620 , China
| | - Suna Fan
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, International Joint Laboratory for Advanced Fiber and Low-Dimension Materials , College of Materials Science and Engineering, Donghua University , Shanghai , 201620 , China
| | - Huili Shao
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, International Joint Laboratory for Advanced Fiber and Low-Dimension Materials , College of Materials Science and Engineering, Donghua University , Shanghai , 201620 , China
| | - Huihui Zhang
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, International Joint Laboratory for Advanced Fiber and Low-Dimension Materials , College of Materials Science and Engineering, Donghua University , Shanghai , 201620 , China
| | - Rongliang Wu
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, International Joint Laboratory for Advanced Fiber and Low-Dimension Materials , College of Materials Science and Engineering, Donghua University , Shanghai , 201620 , China
| | - Benjamin S Hsiao
- Department of Chemistry , Stony Brook University , Stony Brook , New York 11794-3400 , United States
| | - Yaopeng Zhang
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, International Joint Laboratory for Advanced Fiber and Low-Dimension Materials , College of Materials Science and Engineering, Donghua University , Shanghai , 201620 , China
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11
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Yazawa K, Malay AD, Masunaga H, Numata K. Role of Skin Layers on Mechanical Properties and Supercontraction of Spider Dragline Silk Fiber. Macromol Biosci 2018; 19:e1800220. [PMID: 30230228 DOI: 10.1002/mabi.201800220] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 07/30/2018] [Indexed: 11/07/2022]
Abstract
Spider dragline silk is a composite biopolymer that harbors extraordinary mechanical characteristics, and consists of a hierarchically arranged protein core surrounded by outer "skin" layers. However, the contribution of the successive fiber layers on material properties has not been well defined. Here, the influence of the different components on the physicochemical and mechanical properties of dragline is investigated. The crystal structure and the mechanical properties are not changed significantly after the removal of skin constituents, indicating that the core region of dragline silk fibers determines the structural and mechanical properties. Furthermore, the outer layers have little influence on supercontraction, suggesting they do not function as protection against the penetration of water molecules. On the other hand, the outer layers offer some protection against protease digestion. The present study provides insight into how the function and structure of silk fibers are modulated and facilitates the design of silk-inspired functional materials.
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Affiliation(s)
- Kenjiro Yazawa
- Biomacromolecules Research Team, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan
| | - Ali D Malay
- Biomacromolecules Research Team, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan
| | - Hiroyasu Masunaga
- Japan Synchrotron Radiation Research Institute, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5198, Japan.,RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5198, Japan
| | - Keiji Numata
- Biomacromolecules Research Team, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan
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12
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Asakura T, Tasei Y, Matsuda H, Naito A. Dynamics of Alanine Methyl Groups in Alanine Oligopeptides and Spider Dragline Silks with Different Packing Structures As Studied by 13C Solid-State NMR Relaxation. Macromolecules 2018. [DOI: 10.1021/acs.macromol.8b01402] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tetsuo Asakura
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Yugo Tasei
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Hironori Matsuda
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Akira Naito
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
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13
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Zhang W, Ye C, Zheng K, Zhong J, Tang Y, Fan Y, Buehler MJ, Ling S, Kaplan DL. Tensan Silk-Inspired Hierarchical Fibers for Smart Textile Applications. ACS NANO 2018; 12:6968-6977. [PMID: 29932636 PMCID: PMC6501189 DOI: 10.1021/acsnano.8b02430] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Tensan silk, a natural fiber produced by the Japanese oak silk moth ( Antherea yamamai, abbreviated to A. yamamai), features superior characteristics, such as compressive elasticity and chemical resistance, when compared to the more common silk produced from the domesticated silkworm, Bombyx mori ( B. mori). In this study, the "structure-property" relationships within A. yamamai silk are disclosed from the different structural hierarchies, confirming the outstanding toughness as dominated by the distinct mesoscale fibrillar architectures. Inspired by this hierarchical construction, we fabricated A. yamamai silk-like regenerated B. mori silk fibers (RBSFs) with mechanical properties (extensibility and modulus) comparable to natural A. yamamai silk. These RBSFs were further functionalized to form conductive RBSFs that were sensitive to force and temperature stimuli for applications in smart textiles. This study provides a blueprint in exploiting rational designs from A. yamanmai, which is rare and expensive in comparison to the common and cost-effective B. mori silk to empower enhanced material properties.
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Affiliation(s)
- Wenwen Zhang
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Jiangsu Key Lab of Biomass-Based Green Fuel & Chemicals, College of Chemical Engineering, Nanjing Forestry University, Nanjing, 210037, China
- School of Physical Science and Technology, ShanghaiTech University, 393 Middle Huaxia Road, Shanghai 201210, China
| | - Chao Ye
- School of Physical Science and Technology, ShanghaiTech University, 393 Middle Huaxia Road, Shanghai 201210, China
| | - Ke Zheng
- School of Physical Science and Technology, ShanghaiTech University, 393 Middle Huaxia Road, Shanghai 201210, China
| | - Jiajia Zhong
- Shanghai Advanced Research Institute (Zhangjiang Lab), Chinese Academy of Sciences, Shanghai, 201210, China
| | - Yuzhao Tang
- Shanghai Advanced Research Institute (Zhangjiang Lab), Chinese Academy of Sciences, Shanghai, 201210, China
| | - Yimin Fan
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Jiangsu Key Lab of Biomass-Based Green Fuel & Chemicals, College of Chemical Engineering, Nanjing Forestry University, Nanjing, 210037, China
| | - Markus J. Buehler
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Shengjie Ling
- School of Physical Science and Technology, ShanghaiTech University, 393 Middle Huaxia Road, Shanghai 201210, China
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - David L. Kaplan
- Department of Biomedical Engineering, Tufts University, Medford, MA, 02155, USA
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14
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Asakura T, Nishimura A, Tasei Y. Determination of Local Structure of 13C Selectively Labeled 47-mer Peptides as a Model for Gly-Rich Region of Nephila clavipes Dragline Silk Using a Combination of 13C Solid-State NMR and MD Simulation. Macromolecules 2018. [DOI: 10.1021/acs.macromol.8b00536] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Tetsuo Asakura
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Akio Nishimura
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Yugo Tasei
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
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15
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Asakura T, Tasei Y, Aoki A, Nishimura A. Mixture of Rectangular and Staggered Packing Arrangements of Polyalanine Region in Spider Dragline Silk in Dry and Hydrated States As Revealed by 13C NMR and X-ray Diffraction. Macromolecules 2018. [DOI: 10.1021/acs.macromol.7b02627] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Tetsuo Asakura
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Yugo Tasei
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Akihiro Aoki
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Akio Nishimura
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
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16
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Tasei Y, Nishimura A, Suzuki Y, Sato TK, Sugahara J, Asakura T. NMR Investigation about Heterogeneous Structure and Dynamics of Recombinant Spider Silk in the Dry and Hydrated States. Macromolecules 2017. [DOI: 10.1021/acs.macromol.7b01862] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Yugo Tasei
- Department
of Biotechnology, Tokyo University of Agriculture and Technology, 2-24-16, Nakacho, Koganei, Tokyo 184-8588, Japan
| | - Akio Nishimura
- Department
of Biotechnology, Tokyo University of Agriculture and Technology, 2-24-16, Nakacho, Koganei, Tokyo 184-8588, Japan
| | - Yu Suzuki
- Tenure-Track
Program for Innovative Research, University of Fukui, 3-9-1 Bunkyo, Fukui-shi, Fukui 910-8507, Japan
| | - Takehiro K. Sato
- Spiber Inc., 234-1 Mizukami, Kakuganji, Tsuruoka, Yamagata 997-0052, Japan
| | - Junichi Sugahara
- Spiber Inc., 234-1 Mizukami, Kakuganji, Tsuruoka, Yamagata 997-0052, Japan
| | - Tetsuo Asakura
- Department
of Biotechnology, Tokyo University of Agriculture and Technology, 2-24-16, Nakacho, Koganei, Tokyo 184-8588, Japan
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17
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Fang G, Tang Y, Qi Z, Yao J, Shao Z, Chen X. Precise correlation of macroscopic mechanical properties and microscopic structures of animal silks—using Antheraea pernyi silkworm silk as an example. J Mater Chem B 2017; 5:6042-6048. [DOI: 10.1039/c7tb01638g] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The structure of wild silkworm silk can be controlled by reeling rate, thus regulating its mechanical performance from close to spider dragline silk to domestic silkworm silk.
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Affiliation(s)
- Guangqiang Fang
- State Key Laboratory of Molecular Engineering of Polymers
- Collaborative Innovation Centre of Polymers and Polymer Composite Materials
- Department of Macromolecular Science
- Laboratory of Advanced Materials
- Fudan University
| | - Yuzhao Tang
- National Centre for Protein Science Shanghai
- Institute of Biochemistry and Cell Biology
- Shanghai Institutes for Biological Sciences
- Chinese Academy of Sciences
- Shanghai
| | - Zeming Qi
- National Synchrotron Radiation Laboratory
- University of Science and Technology of China
- Hefei
- People's Republic of China
| | - Jinrong Yao
- State Key Laboratory of Molecular Engineering of Polymers
- Collaborative Innovation Centre of Polymers and Polymer Composite Materials
- Department of Macromolecular Science
- Laboratory of Advanced Materials
- Fudan University
| | - Zhengzhong Shao
- State Key Laboratory of Molecular Engineering of Polymers
- Collaborative Innovation Centre of Polymers and Polymer Composite Materials
- Department of Macromolecular Science
- Laboratory of Advanced Materials
- Fudan University
| | - Xin Chen
- State Key Laboratory of Molecular Engineering of Polymers
- Collaborative Innovation Centre of Polymers and Polymer Composite Materials
- Department of Macromolecular Science
- Laboratory of Advanced Materials
- Fudan University
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18
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Riekel C, Burghammer M, Dane TG, Ferrero C, Rosenthal M. Nanoscale Structural Features in Major Ampullate Spider Silk. Biomacromolecules 2016; 18:231-241. [PMID: 28001374 DOI: 10.1021/acs.biomac.6b01537] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Spider major ampullate silk is often schematically represented as a two-phase material composed of crystalline nanodomains in an amorphous matrix. Here we are interested in revealing its more complex nanoscale organization by probing Argiope bruennichi dragline-type fibers using scanning X-ray nanodiffraction. This allows resolving transversal structural features such as an about 1 μm skin layer composed of around 100 nm diameter nanofibrils serving presumably as an elastic sheath. The core consists of a composite of several nm size crystalline nanodomains with poly(l-alanine) microstructure, embedded in a polypeptide network with short-range order. Stacks of nanodomains separated by less ordered nanosegments form nanofibrils with a periodic axial density modulation which is particularly sensitive to radiation damage. The precipitation of larger β-type nanocrystallites in the outer core-shell is attributed to MaSp1 protein molecules.
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Affiliation(s)
- Christian Riekel
- The European Synchrotron (ESRF) , CS40220, F-38043 Grenoble Cedex 9, France
| | - Manfred Burghammer
- The European Synchrotron (ESRF) , CS40220, F-38043 Grenoble Cedex 9, France.,Department of Analytical Chemistry, Ghent University , Krijgslaan 281, S12B-9000 Ghent, Belgium
| | - Thomas G Dane
- The European Synchrotron (ESRF) , CS40220, F-38043 Grenoble Cedex 9, France
| | - Claudio Ferrero
- The European Synchrotron (ESRF) , CS40220, F-38043 Grenoble Cedex 9, France
| | - Martin Rosenthal
- The European Synchrotron (ESRF) , CS40220, F-38043 Grenoble Cedex 9, France
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19
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Boulet-Audet M, Holland C, Gheysens T, Vollrath F. Dry-Spun Silk Produces Native-Like Fibroin Solutions. Biomacromolecules 2016; 17:3198-3204. [PMID: 27526078 PMCID: PMC5059755 DOI: 10.1021/acs.biomac.6b00887] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
![]()
Silk’s
outstanding mechanical properties and energy efficient
solidification mechanisms provide inspiration for biomaterial self-assembly
as well as offering a diverse platform of materials suitable for many
biotechnology applications. Experiments now reveal that the mulberry
silkworm Bombyx mori secretes its silk
in a practically “unspun” state that retains much of
the solvent water and exhibits a surprisingly low degree of molecular
order (β-sheet crystallinity) compared to the state found in
a fully formed and matured fiber. These new observations challenge
the general understanding of silk spinning and in particular the role
of the spinning duct for structure development. Building on this discovery
we report that silk spun in low humidity appears to arrest a molecular
annealing process crucial for β-sheet formation. This, in turn,
has significant positive implications, enabling the production of
a high fidelity reconstituted silk fibroin with properties akin to
the gold standard of unspun native silk.
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Affiliation(s)
- Maxime Boulet-Audet
- Department of Zoology, Oxford University , Oxford, United Kingdom.,Department of Life Sciences, Imperial College London , London, United Kingdom
| | - Chris Holland
- Department of Zoology, Oxford University , Oxford, United Kingdom.,Department of Materials Science and Engineering, The University of Sheffield , Sheffield, United Kingdom
| | - Tom Gheysens
- Department of Zoology, Oxford University , Oxford, United Kingdom.,Department of Organic and Macromolecular Chemistry, University of Ghent , Ghent, Belgium
| | - Fritz Vollrath
- Department of Zoology, Oxford University , Oxford, United Kingdom
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20
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Weatherbee-Martin N, Xu L, Hupe A, Kreplak L, Fudge DS, Liu XQ, Rainey JK. Identification of Wet-Spinning and Post-Spin Stretching Methods Amenable to Recombinant Spider Aciniform Silk. Biomacromolecules 2016; 17:2737-46. [PMID: 27387592 DOI: 10.1021/acs.biomac.6b00857] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Spider silks are outstanding biomaterials with mechanical properties that outperform synthetic materials. Of the six fibrillar spider silks, aciniform (or wrapping) silk is the toughest through a unique combination of strength and extensibility. In this study, a wet-spinning method for recombinant Argiope trifasciata aciniform spidroin (AcSp1) is introduced. Recombinant AcSp1 comprising three 200 amino acid repeat units was solubilized in a 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)/water mixture, forming a viscous α-helix-enriched spinning dope, and wet-spun into an ethanol/water coagulation bath allowing continuous fiber production. Post-spin stretching of the resulting wet-spun fibers in water significantly improved fiber strength, enriched β-sheet conformation without complete α-helix depletion, and enhanced birefringence. These methods allow reproducible aciniform silk fiber formation, albeit with lower extensibility than native silk, requiring conditions and methods distinct from those previously reported for other silk proteins. This provides an essential starting point for tailoring wet-spinning of aciniform silk to achieve desired properties.
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Affiliation(s)
| | | | - Andre Hupe
- Department of Integrative Biology, University of Guelph , Guelph, Ontario N1G 2W1, Canada
| | | | - Douglas S Fudge
- Department of Integrative Biology, University of Guelph , Guelph, Ontario N1G 2W1, Canada
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21
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Numata K, Masunaga H, Hikima T, Sasaki S, Sekiyama K, Takata M. Use of extension-deformation-based crystallisation of silk fibres to differentiate their functions in nature. SOFT MATTER 2015; 11:6335-6342. [PMID: 26166211 DOI: 10.1039/c5sm00757g] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
β-Sheet crystals play an important role in determining the stiffness, strength, and optical properties of silk and in the exhibition of silk-type-specific functions. It is important to elucidate the structural changes that occur during the stretching of silk fibres to understand the functions of different types of fibres. Herein, we elucidate the initial crystallisation behaviour of silk molecules during the stretching of three types of silk fibres using synchrotron radiation X-ray analysis. When spider dragline silk was stretched, it underwent crystallisation and the alignment of the β-sheet crystals became disordered initially but was later recovered. On the other hand, silkworm cocoon silk did not exhibit further crystallisation, whereas capture spiral silk was predominantly amorphous. Structural analyses showed that the crystallisation of silks following extension deformation has a critical effect on their mechanical and optical properties. These findings should aid the production of artificial silk fibres and facilitate the development of silk-inspired functional materials.
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Affiliation(s)
- Keiji Numata
- Enzyme Research Team, Biomass Engineering Program Cooperative Division, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.
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22
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Copeland CG, Bell BE, Christensen CD, Lewis RV. Development of a Process for the Spinning of Synthetic Spider Silk. ACS Biomater Sci Eng 2015; 1:577-584. [PMID: 27064312 DOI: 10.1021/acsbiomaterials.5b00092] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Spider silks have unique mechanical properties but current efforts to duplicate those properties with recombinant proteins have been unsuccessful. This study was designed to develop a single process to spin fibers with excellent and consistent mechanical properties. As-spun fibers produced were brittle, but by stretching the fibers the mechanical properties were greatly improved. A water-dip or water-stretch further increased the strength and elongation of the synthetic spider silk fibers. Given the promising results of the water stretch, a mechanical double-stretch system was developed. Both a methanol/water mixture and an isopropanol/water mixture were independently used to stretch the fibers with this system. It was found that the methanol mixture produced fibers with high tensile strength while the isopropanol mixture produced fibers with high elongation.
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Affiliation(s)
- Cameron G Copeland
- Department of Biological Engineering and Synthetic Biomanufacturing Center, Utah State University, 650 East 1600 North, Logan, Utah 84341, United States
| | - Brianne E Bell
- Department of Biological Engineering and Synthetic Biomanufacturing Center, Utah State University, 650 East 1600 North, Logan, Utah 84341, United States
| | - Chad D Christensen
- Department of Biological Engineering and Synthetic Biomanufacturing Center, Utah State University, 650 East 1600 North, Logan, Utah 84341, United States
| | - Randolph V Lewis
- Department of Biological Engineering and Synthetic Biomanufacturing Center, Utah State University, 650 East 1600 North, Logan, Utah 84341, United States
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23
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Kurut A, Dicko C, Lund M. Dimerization of Terminal Domains in Spiders Silk Proteins Is Controlled by Electrostatic Anisotropy and Modulated by Hydrophobic Patches. ACS Biomater Sci Eng 2015; 1:363-371. [DOI: 10.1021/ab500039q] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Anıl Kurut
- Division of Theoretical Chemistry,
Chemical Center,
and ‡Division of Pure
and Applied Biochemistry, Chemical Center, Lund University, SE-22100 Lund, Sweden
| | - Cedric Dicko
- Division of Theoretical Chemistry,
Chemical Center,
and ‡Division of Pure
and Applied Biochemistry, Chemical Center, Lund University, SE-22100 Lund, Sweden
| | - Mikael Lund
- Division of Theoretical Chemistry,
Chemical Center,
and ‡Division of Pure
and Applied Biochemistry, Chemical Center, Lund University, SE-22100 Lund, Sweden
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24
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Heidebrecht A, Eisoldt L, Diehl J, Schmidt A, Geffers M, Lang G, Scheibel T. Biomimetic fibers made of recombinant spidroins with the same toughness as natural spider silk. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:2189-94. [PMID: 25689835 DOI: 10.1002/adma.201404234] [Citation(s) in RCA: 159] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 01/13/2015] [Indexed: 05/20/2023]
Abstract
Using a self-assembly of recombinant spidroins, biomimetic spinning dopes are produced and wet-spun into fibers. Upon varying the molecular design of the underlying recombinant spidroins, the influence of the amino- and carboxy-terminal domains, as well as the size of the repetitive core domain on fiber mechanics, is determined. Fiber toughness upon biomimetic processing equals and even slightly exceeds that of natural ones.
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Affiliation(s)
- Aniela Heidebrecht
- Lehrstuhl Biomaterialien, Fakultät für Ingenieurwissenschaften, Universität Bayreuth, 95440, Bayreuth, Germany
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25
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Mortimer B, Guan J, Holland C, Porter D, Vollrath F. Linking naturally and unnaturally spun silks through the forced reeling of Bombyx mori. Acta Biomater 2015; 11:247-55. [PMID: 25242653 DOI: 10.1016/j.actbio.2014.09.021] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 08/18/2014] [Accepted: 09/12/2014] [Indexed: 10/24/2022]
Abstract
The forced reeling of silkworms offers the potential to produce a spectrum of silk filaments, spun from natural silk dope and subjected to carefully controlled applied processing conditions. Here we demonstrate that the envelope of stress-strain properties for forced reeled silks can encompass both naturally spun cocoon silk and unnaturally processed artificial silk filaments. We use dynamic mechanical thermal analysis (DMTA) to quantify the structural properties of these silks. Using this well-established mechanical spectroscopic technique, we show high variation in the mechanical properties and the associated degree of disordered hydrogen-bonded structures in forced reeled silks. Furthermore, we show that this disorder can be manipulated by a range of processing conditions and even ameliorated under certain parameters, such as annealing under heat and mechanical load. We conclude that the powerful combination of forced reeling silk and DMTA has tied together native/natural and synthetic/unnatural extrusion spinning. The presented techniques therefore have the ability to define the potential of Bombyx-derived proteins for use in fibre-based applications and serve as a roadmap to improve fibre quality via post-processing.
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26
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Xing C, Munro T, White B, Ban H, Copeland CG, Lewis RV. Thermophysical properties of the dragline silk of Nephila clavipes spider. POLYMER 2014. [DOI: 10.1016/j.polymer.2014.05.046] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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27
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Tucker CL, Jones JA, Bringhurst HN, Copeland CG, Addison JB, Weber WS, Mou Q, Yarger JL, Lewis RV. Mechanical and physical properties of recombinant spider silk films using organic and aqueous solvents. Biomacromolecules 2014; 15:3158-70. [PMID: 25030809 PMCID: PMC4130237 DOI: 10.1021/bm5007823] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Spider
silk has exceptional mechanical and biocompatibility properties.
The goal of this study was optimization of the mechanical properties
of synthetic spider silk thin films made from synthetic forms of MaSp1
and MaSp2, which compose the dragline silk of Nephila
clavipes. We increased the mechanical stress of MaSp1
and 2 films solubilized in both HFIP and water by adding glutaraldehyde
and then stretching them in an alcohol based stretch bath. This resulted
in stresses as high as 206 MPa and elongations up to 35%, which is
4× higher than the as-poured controls. Films were analyzed using
NMR, XRD, and Raman, which showed that the secondary structure after
solubilization and film formation in as-poured films is mainly a helical
conformation. After the post-pour stretch in a methanol/water bath,
the MaSp proteins in both the HFIP and water-based films formed aligned
β-sheets similar to those in spider silk fibers.
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Affiliation(s)
- Chauncey L Tucker
- Departments of †Biological Engineering and ‡Biology, Utah State University , Logan, Utah 84322, United States
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28
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Reichheld SE, Muiznieks LD, Stahl R, Simonetti K, Sharpe S, Keeley FW. Conformational transitions of the cross-linking domains of elastin during self-assembly. J Biol Chem 2014; 289:10057-68. [PMID: 24550393 DOI: 10.1074/jbc.m113.533893] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Elastin is the intrinsically disordered polymeric protein imparting the exceptional properties of extension and elastic recoil to the extracellular matrix of most vertebrates. The monomeric precursor of elastin, tropoelastin, as well as polypeptides containing smaller subsets of the tropoelastin sequence, can self-assemble through a colloidal phase separation process called coacervation. Present understanding suggests that self-assembly is promoted by association of hydrophobic domains contained within the tropoelastin sequence, whereas polymerization is achieved by covalent joining of lysine side chains within distinct alanine-rich, α-helical cross-linking domains. In this study, model elastin polypeptides were used to determine the structure of cross-linking domains during the assembly process and the effect of sequence alterations in these domains on assembly and structure. CD temperature melts indicated that partial α-helical structure in cross-linking domains at lower temperatures was absent at physiological temperature. Solid-state NMR demonstrated that β-strand structure of the cross-linking domains dominated in the coacervate state, although α-helix was predominant after subsequent cross-linking of lysine side chains with genipin. Mutation of lysine residues to hydrophobic amino acids, tyrosine or alanine, leads to increased propensity for β-structure and the formation of amyloid-like fibrils, characterized by thioflavin-T binding and transmission electron microscopy. These findings indicate that cross-linking domains are structurally labile during assembly, adapting to changes in their environment and aggregated state. Furthermore, the sequence of cross-linking domains has a dramatic effect on self-assembly properties of elastin-like polypeptides, and the presence of lysine residues in these domains may serve to prevent inappropriate ordered aggregation.
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Affiliation(s)
- Sean E Reichheld
- From the Molecular Structure and Function Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario M5G 1X8 and
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29
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Davies G, Knight D, Vollrath F. Structure and function of the major ampullate spinning duct of the golden orb weaver, Nephila edulis. Tissue Cell 2013; 45:306-11. [DOI: 10.1016/j.tice.2013.04.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 04/03/2013] [Indexed: 10/26/2022]
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30
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Mechanical properties and structure of silkworm cocoons: A comparative study of Bombyx mori, Antheraea assamensis, Antheraea pernyi and Antheraea mylitta silkworm cocoons. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2013; 33:3206-13. [DOI: 10.1016/j.msec.2013.03.051] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 01/17/2013] [Accepted: 03/29/2013] [Indexed: 11/17/2022]
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31
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Ling S, Qi Z, Knight DP, Huang Y, Huang L, Zhou H, Shao Z, Chen X. Insight into the structure of single Antheraea pernyi silkworm fibers using synchrotron FTIR microspectroscopy. Biomacromolecules 2013; 14:1885-92. [PMID: 23607809 DOI: 10.1021/bm400267m] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Synchrotron FTIR (S-FTIR) microspectroscopy was used to monitor both protein secondary structures (conformations) and their orientations in single cocoon silk fibers of the Chinese Tussah silk moth ( Antheraea pernyi ). In addition, to understand further the relationship between structure and properties of single silk fibers, we studied the changes of orientation and content of different secondary structures in single A. pernyi silk fibers when subjected to different strains. The results showed that the content and orientation of β-sheet was almost unchanged for strains from 0 to 0.3. However, the orientation of α-helix and random coil improved progressively with increasing strain, with a parallel decrease in α-helix content and an increase in random coil. This clearly indicates that most of the deformation upon stretching of the single fiber is due to the change of orientation in the amorphous regions coupled with a conversion of some of the α-helix to random coil. These observations provide an explanation for the supercontraction behavior of certain animal silks and are likely to facilitate understanding and optimization of postdrawing used in the conjunction with the wet-spinning of silk fibers from regenerated silk solutions. Thus, our work demonstrates the power of S-FTIR microspectroscopy for studying biopolymers.
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Affiliation(s)
- Shengjie Ling
- State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Laboratory of Advanced Materials, Fudan University , Shanghai, 200433, People's Republic of China
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32
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Holland GP, Mou Q, Yarger JL. Determining hydrogen-bond interactions in spider silk with 1H–13C HETCOR fast MAS solid-state NMR and DFT proton chemical shift calculations. Chem Commun (Camb) 2013; 49:6680-2. [DOI: 10.1039/c3cc43737j] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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33
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Physical Properties, Structure Analysis, and Enzymatic Degradation of Poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] Films and Fibers. ACTA ACUST UNITED AC 2012. [DOI: 10.1021/bk-2012-1114.ch011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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34
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Benmore CJ, Izdebski T, Yarger JL. Total x-ray scattering of spider dragline silk. PHYSICAL REVIEW LETTERS 2012; 108:178102. [PMID: 22680907 DOI: 10.1103/physrevlett.108.178102] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Indexed: 06/01/2023]
Abstract
Total x-ray scattering measurements of spider dragline silk fibers from Nephila clavipes, Argiope aurantia, and Latrodectus hesperus all yield similar structure factors, with only small variations between the different species. Wide-angle x-ray scattering from fibers orientated perpendicular to the beam shows a high degree of anisotropy, and differential pair distribution functions obtained by integrating over wedges of the equatorial and meridian planes indicate that, on average, the majority (95%) of the atom-atom correlations do not extend beyond 1 nm. Futhermore, the atom-atom correlations between 1 and 3 nm are not associated with the most intense diffraction peaks at Q=1-2 Å(-1). Disordered molecular orientations along the fiber axis are consistent with proteins in similar structural arrangements to those in the equatorial plane, which may be associated with the silk's greater flexibility in this direction.
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Affiliation(s)
- C J Benmore
- X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Illinois 60439, USA
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35
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Holland C, O'Neil K, Vollrath F, Dicko C. Distinct structural and optical regimes in natural silk spinning. Biopolymers 2012; 97:368-73. [PMID: 22240893 DOI: 10.1002/bip.22022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Accepted: 12/21/2011] [Indexed: 11/11/2022]
Abstract
This study investigates the relationship between birefringence and mechanical properties in the dragline silk of the gold orb weaving spider Nephila edulis. Using a custom birefringence-tensile testing device, we probed the orientation and water-induced swelling of fibers spun at variety of drawing rates ranging from 0.003 to 400 mm s(-1). Our results indicate that based upon drawing rate, silk fibers fall into three distinct regimes each with characteristic orientation and swelling properties. Further investigation using in situ tensile testing reveals interactions between a fiber's drawing speed, mechanical properties, and orientation that support previous model predictions. We propose that simultaneous birefringence-tensile testing provides a unique and readily accessible insight into the structural behavior of this interesting and important biomaterial.
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Affiliation(s)
- Chris Holland
- Department of Zoology, Oxford University, Oxford OX1 3PS, UK
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36
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Cloutier I, Leclerc J, Lefèvre T, Auger M. Solid-state nuclear magnetic resonance (NMR) spectroscopy reveals distinctive protein dynamics in closely related spider silks. CAN J CHEM 2011. [DOI: 10.1139/v11-036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Structurally closely related spider silks, namely, major ampullate silk (MaS) reeled at 0.5 and 10 cm/s, minor ampullate silk (MiS), and cocoon silk have been investigated by solid-state nuclear magnetic resonance (NMR). These silks exhibit different mechanical properties that are not well explained with current structural data. NMR spectra confirm that the secondary structures of these silks are similar, but that differing relaxation dynamics exist at the alanine, glycine, and glutamine residue level. MaS reeled rapidly is made of more mobile proteins in both the β-sheet and amorphous regions, suggesting that reeling speed alters molecular rearrangement during spinning, with the chain packing being less organized in the fastpull fiber. Alanine and glycine relaxation dynamics increases as MaS < MiS < cocoon silk, showing that the whole fiber displays distinctive protein dynamics, chain packing, and intermolecular interactions. Besides molecular orientation, silk extensibility is related to a more mobile structural organization.
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Affiliation(s)
- Isabelle Cloutier
- Department of Chemistry, Regroupement québécois de recherche sur la fonction, la structure et l’ingénierie des protéines (PROTEO), Centre de recherche sur les matériaux avancés (CERMA), Université Laval, Quebec, QC G1V 0A6, Canada
| | - Jérémie Leclerc
- Department of Chemistry, Regroupement québécois de recherche sur la fonction, la structure et l’ingénierie des protéines (PROTEO), Centre de recherche sur les matériaux avancés (CERMA), Université Laval, Quebec, QC G1V 0A6, Canada
| | - Thierry Lefèvre
- Department of Chemistry, Regroupement québécois de recherche sur la fonction, la structure et l’ingénierie des protéines (PROTEO), Centre de recherche sur les matériaux avancés (CERMA), Université Laval, Quebec, QC G1V 0A6, Canada
| | - Michèle Auger
- Department of Chemistry, Regroupement québécois de recherche sur la fonction, la structure et l’ingénierie des protéines (PROTEO), Centre de recherche sur les matériaux avancés (CERMA), Université Laval, Quebec, QC G1V 0A6, Canada
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37
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Ling S, Qi Z, Knight DP, Shao Z, Chen X. Synchrotron FTIR microspectroscopy of single natural silk fibers. Biomacromolecules 2011; 12:3344-9. [PMID: 21790142 DOI: 10.1021/bm2006032] [Citation(s) in RCA: 164] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Synchrotron FTIR (S-FTIR) microspectroscopy was used to monitor the silk protein conformation in a range of single natural silk fibers (domestic and wild silkworm and spider dragline silk). With the selection of suitable aperture size, we obtained high-resolution S-FTIR spectra capable of semiquantitative analysis of protein secondary structures. For the first time, we have determined from S-FTIR the β-sheet content in a range of natural single silk fibers, 28 ± 4, 23 ± 2, and 17 ± 4% in Bombyx mori, Antheraea pernyi, and Nephila edulis silks, respectively. The trend of β-sheet content in different silk fibers from the current study accords quite well with published data determined by XRD, Raman, and (13)C NMR. Our results indicate that the S-FTIR microspectroscopy method has considerable potential for the study of single natural silk fibers.
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Affiliation(s)
- Shengjie Ling
- The Key Laboratory of Molecular Engineering of Polymers of MOE, Department of Macromolecular Science, Laboratory of Advanced Materials, Fudan University, Shanghai, 200433, China
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Müller C, Jansson R, Elfwing A, Askarieh G, Karlsson R, Hamedi M, Rising A, Johansson J, Inganäs O, Hedhammar M. Functionalisation of recombinant spider silk with conjugated polyelectrolytes. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c0jm03270k] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Spiess K, Ene R, Keenan CD, Senker J, Kremer F, Scheibel T. Impact of initial solvent on thermal stability and mechanical properties of recombinant spider silk films. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c1jm11700a] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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40
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Riekel C, Burghammer M, Davies R. Progress in micro- and nano-diffraction at the ESRF ID13 beamline. ACTA ACUST UNITED AC 2010. [DOI: 10.1088/1757-899x/14/1/012013] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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41
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Koopmans RJ. Nanobiotechnology. Ind Biotechnol (New Rochelle N Y) 2010. [DOI: 10.1002/9783527630233.ch7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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42
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Gellynck K, Verdonk PCM, Van Nimmen E, Almqvist KF, Gheysens T, Schoukens G, Van Langenhove L, Kiekens P, Mertens J, Verbruggen G. Silkworm and spider silk scaffolds for chondrocyte support. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2008; 19:3399-3409. [PMID: 18545943 DOI: 10.1007/s10856-008-3474-6] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2008] [Accepted: 05/15/2008] [Indexed: 05/26/2023]
Abstract
OBJECTIVE To create scaffolds with silkworm cocoon, spider egg sac and spider dragline silk fibres and examine their use for chondrocyte attachment and support. METHODS Three different kinds of scaffolds were developed with Bombyx mori cocoon, Araneus diadematus egg sac and dragline silk fibres. The attachment of human articular cartilage cells were investigated on these bioprotein matrices. The chondrocytes produced an extracellular matrix which was studied by immunostaining. Moreover, the compression behaviour in relation to the porosity was studied. RESULTS The compression modulus of a silkworm silk scaffold was related to its porosity. Chondrocytes were able to attach and to grow on the different fibres and in the scaffolds for several weeks while producing extracellular matrix products. CONCLUSION Porous scaffolds can be made out of silkworm and spider silk for cartilage regeneration. Mechanical properties are related to porosity and pore size of the construct. Cell spreading and cell expression depended on the porosity and pore-size.
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Affiliation(s)
- Kris Gellynck
- Department of Textiles, Ghent University, Technology Park 9, 9052, Zwijnaarde, Belgium.
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Ulrich S, Glišović A, Salditt T, Zippelius A. Diffraction from the beta-sheet crystallites in spider silk. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2008; 27:229-242. [PMID: 18843512 DOI: 10.1140/epje/i2008-10374-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 07/11/2008] [Indexed: 05/26/2023]
Abstract
We analyze the wide-angle X-ray scattering from oriented spider silk fibers in terms of a quantitative scattering model, including both structural and statistical parameters of the beta-sheet crystallites of spider silk in the amorphous matrix. The model is based on kinematic scattering theory and allows for rather general correlations of the positional and orientational degrees of freedom, including the crystallite's size, composition and dimension of the unit cell. The model is evaluated numerically and compared to experimental scattering intensities allowing us to extract the geometric and statistical parameters. We show explicitly that for the experimentally found mosaicity (width of the orientational distribution) intercrystallite effects are negligible and the data can be analyzed in terms of single-crystallite scattering, as is usually assumed in the literature.
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Affiliation(s)
- S Ulrich
- Institut für Theoretische Physik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
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44
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MacIntosh AC, Kearns VR, Crawford A, Hatton PV. Skeletal tissue engineering using silk biomaterials. J Tissue Eng Regen Med 2008; 2:71-80. [PMID: 18383453 DOI: 10.1002/term.68] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Silks have been proposed as potential scaffold materials for tissue engineering, mainly because of their physical properties. They are stable at physiological temperatures, flexible and resist tensile and compressive forces. Bombyx mori (silkworm) cocoon silk has been used as a suture material for over a century, and has proved to be biocompatible once the immunogenic sericin coating is removed. Spider silks have a similar structure to silkworm silk but do not have a sericin coating. This paper provides a general overview on the use of silk protein in biomaterials, with a focus on skeletal tissue engineering.
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Affiliation(s)
- Ana C MacIntosh
- Centre for Biomaterials and Tissue Engineering, School of Clinical Dentistry, University of Sheffield, Sheffield, UK
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45
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Brooks AE, Nelson SR, Jones JA, Koenig C, Hinman M, Stricker S, Lewis RV. Distinct contributions of model MaSp1 and MaSp2 like peptides to the mechanical properties of synthetic major ampullate silk fibers as revealed in silico. Nanotechnol Sci Appl 2008; 1:9-16. [PMID: 20657704 DOI: 10.2147/nsa.s3961] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
All characterized major ampullate silks from orb-web weaving spiders are composites of primarily two different proteins: MaSp1 and MaSp2. The conserved association of MaSp1 and MaSp2 in these spider species, the highly conserved amino acid motifs, and variable ratios of MaSp1 to MaSp2 demonstrate the importance of both MaSp1 and MaSp2 to the strength and elasticity of the fiber. Computer simulated mechanical tests predicted differing roles for MaSp1 and MaSp2 in the mechanical properties of the fibers. Recombinant MaSp1 and MaSp2 proteins were blended and spun into fibers mimicking the computer-simulated conditions. Mechanical testing verified the differing roles of MaSp1 and MaSp2.
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Affiliation(s)
- Amanda E Brooks
- Department of Molecular Biology, University of Wyoming, Laramie, WY, USA
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46
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Glišović A, Vehoff T, Davies RJ, Salditt T. Strain Dependent Structural Changes of Spider Dragline Silk. Macromolecules 2007. [DOI: 10.1021/ma070528p] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anja Glišović
- Institut für Röntgenphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany, and 2 ESRF, 6 Rue Jules Horowitz, BP220, 38043 Grenoble Cedex, France
| | - Thorsten Vehoff
- Institut für Röntgenphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany, and 2 ESRF, 6 Rue Jules Horowitz, BP220, 38043 Grenoble Cedex, France
| | - Richard J. Davies
- Institut für Röntgenphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany, and 2 ESRF, 6 Rue Jules Horowitz, BP220, 38043 Grenoble Cedex, France
| | - Tim Salditt
- Institut für Röntgenphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany, and 2 ESRF, 6 Rue Jules Horowitz, BP220, 38043 Grenoble Cedex, France
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47
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Dicko C, Porter D, Bond J, Kenney JM, Vollrath F. Structural Disorder in Silk Proteins Reveals the Emergence of Elastomericity. Biomacromolecules 2007; 9:216-21. [DOI: 10.1021/bm701069y] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Cedric Dicko
- Department of Zoology, Oxford University, OX1 3PS, U.K., Department of Biology, East Carolina University, Greenville, North Carolina 27858, and Department of Physics, East Carolina University, Greenville, North Carolina 27858
| | - David Porter
- Department of Zoology, Oxford University, OX1 3PS, U.K., Department of Biology, East Carolina University, Greenville, North Carolina 27858, and Department of Physics, East Carolina University, Greenville, North Carolina 27858
| | - Jason Bond
- Department of Zoology, Oxford University, OX1 3PS, U.K., Department of Biology, East Carolina University, Greenville, North Carolina 27858, and Department of Physics, East Carolina University, Greenville, North Carolina 27858
| | - John M. Kenney
- Department of Zoology, Oxford University, OX1 3PS, U.K., Department of Biology, East Carolina University, Greenville, North Carolina 27858, and Department of Physics, East Carolina University, Greenville, North Carolina 27858
| | - Fritz Vollrath
- Department of Zoology, Oxford University, OX1 3PS, U.K., Department of Biology, East Carolina University, Greenville, North Carolina 27858, and Department of Physics, East Carolina University, Greenville, North Carolina 27858
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48
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Nozue Y, Shinohara Y, Amemiya Y. Application of Microbeam Small- and Wide-angle X-ray Scattering to Polymeric Material Characterization. Polym J 2007. [DOI: 10.1295/polymj.pj2007077] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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49
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Sponner A, Vater W, Monajembashi S, Unger E, Grosse F, Weisshart K. Composition and hierarchical organisation of a spider silk. PLoS One 2007; 2:e998. [PMID: 17912375 PMCID: PMC1994588 DOI: 10.1371/journal.pone.0000998] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2007] [Accepted: 09/11/2007] [Indexed: 11/19/2022] Open
Abstract
Albeit silks are fairly well understood on a molecular level, their hierarchical organisation and the full complexity of constituents in the spun fibre remain poorly defined. Here we link morphological defined structural elements in dragline silk of Nephila clavipes to their biochemical composition and physicochemical properties. Five layers of different make-ups could be distinguished. Of these only the two core layers contained the known silk proteins, but all can vitally contribute to the mechanical performance or properties of the silk fibre. Understanding the composite nature of silk and its supra-molecular organisation will open avenues in the production of high performance fibres based on artificially spun silk material.
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Affiliation(s)
- Alexander Sponner
- Department of Zoology, University of Oxford, Oxford, United Kingdom
- Leibniz Institute for Age Research, Fritz Lipmann Institute, Jena, Germany
| | - Wolfram Vater
- Leibniz Institute for Age Research, Fritz Lipmann Institute, Jena, Germany
| | | | - Eberhard Unger
- Leibniz Institute for Age Research, Fritz Lipmann Institute, Jena, Germany
| | - Frank Grosse
- Leibniz Institute for Age Research, Fritz Lipmann Institute, Jena, Germany
| | - Klaus Weisshart
- Leibniz Institute for Age Research, Fritz Lipmann Institute, Jena, Germany
- * To whom correspondence should be addressed. E-mail:
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50
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Chen X, Shao Z, Knight DP, Vollrath F. Conformation transition kinetics of Bombyx mori silk protein. Proteins 2007; 68:223-31. [PMID: 17436322 DOI: 10.1002/prot.21414] [Citation(s) in RCA: 156] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Time-resolved FTIR analysis was used to monitor the conformation transition induced by treating regenerated Bombyx mori silk fibroin films and solutions with different concentrations of ethanol. The resulting curves showing the kinetics of the transition for both films and fibroin solutions were influenced by the ethanol concentration. In addition, for silk fibroin solutions the protein concentration also had an effect on the kinetics. At low ethanol concentrations (for example, less than 40% v/v in the case of film), films and fibroin solutions showed a phase in which beta-sheets slowly formed at a rate dependent on the ethanol concentration. Reducing the concentration of the fibroin in solutions also slowed the formation of beta-sheets. These observations suggest that this phase represents a nucleation step. Such a nucleation phase was not seen in the conformation transition at ethanol concentrations > 40% in films or > 50% in silk fibroin solutions. Our results indicate that the ethanol-induced conformation transition of silk fibroin in films and solutions is a three-phase process. The first phase is the initiation of beta-sheet structure (nucleation), the second is a fast phase of beta-sheet growth while the third phase represents a slow perfection of previously formed beta-sheet structure. The nucleation step can be very fast or relatively slow, depending on factors that influence protein chain mobility and intermolecular hydrogen bond formation. The findings give support to the previous evidence that natural silk spinning in silkworms is nucleation-dependent, and that silkworms (like spiders) use concentrated silk protein solutions, and careful control of the pH value and metallic ion content of the processing environment to speed up the nucleation step to produce a rapid conformation transition to convert the water soluble spinning dope to a tough solid silk fiber.
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Affiliation(s)
- Xin Chen
- The Key Laboratory of Molecular Engineering of Polymers of MOE, Department of Macromolecular Science, Fudan University, Shanghai 200433, People's Republic of China.
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