| POLYMERS Vol.67 No.3 |
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COVER STORY
Structural Protein: Near & Dear Future Structural Material |
| COVER STORY: Highlight Reviews |
| Recent Advances in Research of Silk Structure and Fiber Formation Mechanism | Tetsuo ASAKURA |
| <Abstract> A major increase in our understanding of the structure and fiber formation mechanism of Bombyx mori silk fibroin was seen mainly using 13C solid-state NMR. The determination of the Silk I (the structure before spinning) and Silk II (the structure after spinning) structures are the starting point for discussion of production of man-made silk fibroin, the origin of the strong silk fiber, and the mechanism of fiber formation in vivo. We now have reasonably good structure models of Silk I (A repeated type II β-turn structure) and Silk II (A heterogeneous structure with mixture of anti-parallel β-sheet and distorted β-turn, and the crystalline domains of 56% of Silk II take two kinds of β-sheet structures with different packing structures). Based on this knowledge the fiber formation mechanism was studied on the basis of the reconstructed spinneret image and the MD simulation about the structure transition from Silk I to Silk II by considering the external forces applied to the silk fibroin in silkworm. Future planned research works are also discussed. Keywords: Bombyx Mori Silk Fibroin / Silk I Structure / Silk II Structure / Fiber Formation Mechanism / 13C Solid-State NMR / Repeated β-turn Structure / Anti-Parallel β-sheet Structure |
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| Super High-Function Structural Proteins to Transform the Basic Materials Industry | Takane SUZUKI |
| <Abstract> Conventional manufacturing industries are dependent on oil, metals, ceramics and other natural resources that may be exhausted in the future. The goal of this program is to learn from the natural world and create super high-function next-generation materials that will dramatically improve Japan’s industrial competitiveness. For example, genes for producing super high-function structural proteins that surpass spider’s silk, which has 340 times the toughness of steel by weight, will be implanted into microorganisms to enable synthetic mass-production. The mechanisms that produce performance on a different dimension will be identified to establish the foundation for new material design and processing technologies, in order to bring about an industrial revolution in materials and free ourselves from the existing structure of industry. In this article, I’d like to report the achievements of our program, especially the composite materials made by protein materials and resins. Keywords: Structural Protein / Spider Silk / Industrial Materials / Composite Materials |
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| Crystal and Higher-Order Structure and Physical Property of Silk | Kohji TASHIRO, Taiyo YOSHIOKA |
| <Abstract> The crystal structures of the α-helix and β-pleated sheets are reviewed for the Bombyx mori silk fibroin and spider dragline silk. Such characteristic property as supercontraction is discussed in relation to the higher-order structure of silk fibroin and spidron. Keywords: Bombyx Mori / Silk / Spider Dragline / Crystal Structure / α-Helix / β-Pleated Sheet / X-ray Structure Analysis |
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| COVER STORY: Topics and Products |
| Comprehensive Sequencing of Spider Silk Genes | Kazuharu ARAKAWA |
| <Abstract> Spider silks are protein materials that exhibit extraordinary mechanical properties including tensile strengths, extensibilities, and toughness, with potential applications in industry as renewable materials. Spiders produce seven types of silks, each composed of specific proteins called spidroins, majority of which are known to be monophyletic. Therefore, if we can obtain a multitude of spidroin sequences along with the mechanical properties of corresponding silks from diverse samples among the order Araneae, we can potentially identify quantitative linkages between sequence motifs and the physical properties. To this end, we are currently underway to sequence 1,000 spiders using de novo transcriptome sequencing and assembly strategy. Here we provide an overview of the project. Keywords: Spider Silks / Fibroins / Sequencing / Nanopore |
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| Proteins: The Next-Generation of Industrial Materials | Junichi SUGAHARA |
| <Abstract> Structural proteins are recently gathering attention as high-performance, designable, sustainable polymers of the future. In nature we see many provocative examples, such as the fibroin found within spider silk, or resilin, sometimes called a “super rubber.” If these proteins could be synthesized cheaply and at a mass scale, there would be significant potential to allow for totally new and unique application development efforts and to realize a more sustainable society. This article will touch on the potential of fibroin and other structural proteins, as well as the global synthesis and commercialization landscape. It will also introduce our efforts relating to the production and processing technologies, as well as the application development of synthetic structural protein materials. Keywords: Synthetic Biology / Structural Protein / Fibroin / Fiber / Resin / Film / Venture Business |
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| Co-Creation Silk between Human and Insect | Tsunenori KAMEDA, Kei KOJIMA |
| <Abstract> Genetic modification technology, a method of modern biotechnology, makes it possible for molecular design of silk protein. The desired proteins can be biosynthesised and spun into silk fibroin by transgenic silkworms. Our group cloned the spider dragline protein gene and generated a transgenic silkworm that produces the cocoon silk through fusion of fibroin heavy chain and spider dragline protein. On the other hand, in nature, a large variety of silk proteins exists. Most of such silks are produced by unknown and/or unused silk worms. In these silks, there is a probable existence of proteins that meet the satisfaction of our demand. When the silk forming coiled-coil structure is desired, the aculeate (stinging) insects, such as honeybee and hornet, become best candidates. Our group developed techniques to regerenate and fabricate the silk produced by hornet’s larvae (hornet silk). The silk fibers and fabrics can be produced by co-creation between human and insect. Keywords: Silk / Bombyx Mori Silkworm / Gene Modification / Transgenic / Coiled Coil / Hornet Silk |
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| Polymer Science and I: A Personal Account |
| Extended My World by Different Fields | Ken-ichi SENO |
| <Abstract> I have been interested in various fields and enjoyed those since my school days. The knowledge and skill of different fields have been very useful for my research and work so far. In this essay, I will introduce my experiences and explain how helpful they are. |
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| Front-Line Polymer Science |
| Polymeric Materials used in Regenerative Medicine | Shoei SANO, Takamasa SAKAI |
| <Abstract> Currently, regenerative medicine draws great attention as next generation medical treatment. Regenerative medicine is defined as medical treatment that successfully enhances the self-healing ability of a living body and restores structure and function of damaged tissues and organs. Today, as regenerative medicine methods, tissue regeneration using pluripotent stem cells (ES cells, iPS cells) and self-tissue induction using cell scaffolds are two major pillars. In regenerative medicine, a scaffold material that allows cell attachment / invasion is indispensable. Polymeric substrates, sponge-like porous bodies, and hydrogels are widely used as scaffolds. In this paper, we introduce the current state of regenerative medicine and polymer materials used there. Keywords: Regerative Medicine / Polymeric Scaffold / Bone / Cartilage / Brain / Nerve |
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