901
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Casem ML, Tran LPP, Moore AMF. Ultrastructure of the major ampullate gland of the black widow spider, Latrodectus hesperus. Tissue Cell 2002; 34:427-36. [PMID: 12441095 DOI: 10.1016/s0040816602000836] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Silk production in the spider occurs within specialized glands that are capable of the synthesis of large fibrous proteins and the post-translational processing of those proteins to form an insoluble fiber. The major ampullate gland of Latrodectus hesperus (black widow) is similar in morphology to those found in the Araneid spiders. The tail domain of this gland is highly protein synthetic, giving rise to a core, fibrous protein product. In addition to a storage function, the ampulla region also synthesizes and exports an electron dense material that appears to form a 'coat' surrounding the silk generated within the tail. The duct of the gland consists of at least two distinct cell types: one type contains 'honeycomb' vesicles of unknown function, while the other possesses elaborate apical microvilli that may be involved in the reabsorption of water and subsequent dehydration of the silk. As the silk product transits through these various stages of assembly, it can been seen to undergo a condensation or concentration, possibly reflecting the influence of both the shear forces induced by movement into the duct and the dehydration that is thought to occur there.
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Affiliation(s)
- Merri Lynn Casem
- Department of Biological Science, California State University, 92834-6850, Fullerton, CA, USA.
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902
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Yamane T, Umemura K, Asakura T. The Structural Characteristics of Bombyx mori Silk Fibroin before Spinning As Studied with Molecular Dynamics Simulation. Macromolecules 2002. [DOI: 10.1021/ma0209390] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Tsutomu Yamane
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Kôsuke Umemura
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Tetsuo Asakura
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
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903
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Round AN, Berry M, McMaster TJ, Stoll S, Gowers D, Corfield AP, Miles MJ. Heterogeneity and persistence length in human ocular mucins. Biophys J 2002; 83:1661-70. [PMID: 12202389 PMCID: PMC1302262 DOI: 10.1016/s0006-3495(02)73934-9] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Atomic force microscopy (AFM) has been used to investigate the heterogeneity and flexibility of human ocular mucins and their subunits. We have paid particular attention, in terms of theory and experiment, to the problem of inducing the polymers to assume equilibrium conformations at a surface. Mucins deposited from a buffer containing Ni(2+) ions adopt extended conformations on mica akin to those observed for DNA under similar conditions. The heterogeneity of the intracellular native mucins is evident from a histogram of contour lengths, reflecting, in part, the diversity of mucin gene products expressed. Reduction of the native mucin with dithiothreitol, thereby breaking the S==S bonds between cysteine residues, causes a marked reduction in polymer length. These results reflect the modes of transport and assembly of newly synthesized mucins in vivo. By modifying the worm-like chain model for applicability to two dimensions, we have confirmed that under the conditions employed mucin adsorbs to mica in an equilibrated conformation. The determined persistence length of the native mucin, 36 nm, is consistent with that of an extended, flexible polymer; such characteristics will influence the properties of the gels formed in vivo.
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Affiliation(s)
- A N Round
- H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom.
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904
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Abstract
Commercial silkworm silk is presumed to be much weaker and less extensible than spider dragline silk, which has been hailed as a 'super-fibre'. But we show here that the mechanical properties of silkworm silks can approach those of spider dragline silk when reeled under controlled conditions. We suggest that silkworms might be able to produce threads that compare well with spider silk by changing their spinning habits, rather than by having their silk genes altered.
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Affiliation(s)
- Zhengzhong Shao
- Department of Macromolecular Science and Key Laboratory of Polymer Engineering of Education Ministry, Fudan University, Shanghai 200433, China.
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905
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van Beek JD, Hess S, Vollrath F, Meier BH. The molecular structure of spider dragline silk: folding and orientation of the protein backbone. Proc Natl Acad Sci U S A 2002; 99:10266-71. [PMID: 12149440 PMCID: PMC124902 DOI: 10.1073/pnas.152162299] [Citation(s) in RCA: 343] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The design principles of spider dragline silk, nature's high-performance fiber, are still largely unknown, in particular for the noncrystalline glycine-rich domains, which form the bulk of the material. Here we apply two-dimensional solid-state NMR to determine the distribution of the backbone torsion angles (phi,psi) as well as the orientation of the polypeptide backbone toward the fiber at both the glycine and alanine residues. Instead of an "amorphous matrix," suggested earlier for the glycine-rich domains, these new data indicate that all domains in dragline silk have a preferred secondary structure and are strongly oriented, with the chains predominantly parallel to the fiber. As proposed previously, the alanine residues are predominantly found in a beta sheet conformation. The glycine residues are partly incorporated into the beta sheets and otherwise form helical structures with an approximate 3-fold symmetry.
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Affiliation(s)
- J D van Beek
- Physical Chemistry, Eidgenössische Technische Hochschule Zurich, CH-8093 Zurich, Switzerland
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906
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Kenney JM, Knight D, Wise MJ, Vollrath F. Amyloidogenic nature of spider silk. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:4159-63. [PMID: 12180993 DOI: 10.1046/j.1432-1033.2002.03112.x] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In spiders soluble proteins are converted to form insoluble silk fibres, stronger than steel. The final fibre product has long been the subject of study; however, little is known about the conversion process in the silk-producing gland of the spider. Here we describe a study of the conversion of the soluble form of the major spider-silk protein, spidroin, directly extracted from the silk gland, to a beta-sheet enriched state using circular dichroism (CD) spectroscopy. Combined with electron microscopy (EM) data showing fibril formation in the beta-sheet rich region of the gland and amino-acid sequence analyses linking spidroin and amyloids, these results lead us to suggest that the refolding conversion is amyloid like. We also propose that spider silk could be a valuable model system for testing hypotheses concerning beta-sheet formation in other fibrilogenic systems, including amyloids.
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Affiliation(s)
- John M Kenney
- Institute for Storage Ring Facilities, University of Aarhus, Denmark.
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907
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Chen X, Knight DP, Vollrath F. Rheological characterization of nephila spidroin solution. Biomacromolecules 2002; 3:644-8. [PMID: 12099805 DOI: 10.1021/bm0156126] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report the results of an investigation into the rheology of solutions of natural spider silk dope (spinning solution). We demonstrate that dilute dope solutions showed only shear thinning as the shear rate increased while more concentrated solutions showed an initial shear thinning followed by a shear thickening and a subsequent decline in viscosity. The critical shear rate for shear thickening depended on dope concentration and was very low in concentrated solutions. This helps to explain how spiders are able to spin silk at very low draw rates and why they use a very concentrated dope solution. We also show that the optimum shear rate for shear thickening in moderately concentrated solutions occurred at pH 6.3 close to the observed pH at the distal end of the spider's spinning duct. Finally, we report that the addition of K(+) ions to dilute dope solutions produced a spontaneous formation of nanofibrils that subsequently aggregated and precipitated. This change was not seen after the addition of other common cations. Taken together, these observations support the hypothesis that the secretion of H(+) and K(+) by the spider's duct together with moderate strain rates produced during spinning induce a phase separation in the silk dope in which the silk protein (spidroin) molecules are converted into insoluble nanofibrils.
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Affiliation(s)
- Xin Chen
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
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908
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Oroudjev E, Soares J, Arcdiacono S, Thompson JB, Fossey SA, Hansma HG. Segmented nanofibers of spider dragline silk: atomic force microscopy and single-molecule force spectroscopy. Proc Natl Acad Sci U S A 2002; 99 Suppl 2:6460-5. [PMID: 11959907 PMCID: PMC128550 DOI: 10.1073/pnas.082526499] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Despite its remarkable materials properties, the structure of spider dragline silk has remained unsolved. Results from two probe microscopy techniques provide new insights into the structure of spider dragline silk. A soluble synthetic protein from dragline silk spontaneously forms nanofibers, as observed by atomic force microscopy. These nanofibers have a segmented substructure. The segment length and amino acid sequence are consistent with a slab-like shape for individual silk protein molecules. The height and width of nanofiber segments suggest a stacking pattern of slab-like molecules in each nanofiber segment. This stacking pattern produces nano-crystals in an amorphous matrix, as observed previously by NMR and x-ray diffraction of spider dragline silk. The possible importance of nanofiber formation to native silk production is discussed. Force spectra for single molecules of the silk protein demonstrate that this protein unfolds through a number of rupture events, indicating a modular substructure within single silk protein molecules. A minimal unfolding module size is estimated to be around 14 nm, which corresponds to the extended length of a single repeated module, 38 amino acids long. The structure of this spider silk protein is distinctly different from the structures of other proteins that have been analyzed by single-molecule force spectroscopy, and the force spectra show correspondingly novel features.
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Affiliation(s)
- E Oroudjev
- Department of Physics, University of California, Santa Barbara, CA 93106, USA
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909
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Termonia Y. Sphere-to-cylinder transition in dilute solutions of diblock copolymers. ACTA ACUST UNITED AC 2002. [DOI: 10.1002/polb.10158] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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910
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Affiliation(s)
- David L Kaplan
- Department of Chemical and Biological Engineering, Bioengineering Center, Tufts University, Medford, MA 02155, USA.
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911
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Abstract
The Sicarid spider Loxosceles laeta spins broad but very thin ribbons of elastic silk that it uses to form a retreat and to capture prey. A structural investigation into this spider's silk and spinning apparatus shows that these ribbons are spun from a gland homologous to the major ampullate gland of orb web spiders. The Loxosceles gland is constructed from the same basic parts (separate transverse zones in the gland, a duct and spigot) as other spider silk glands but construction details are highly specialized. These differences are thought to relate to different ways of spinning silk in the two groups of spiders. Loxosceles uses conventional die extrusion, feeding a liquid dope (spinning solution) to the slit-like die to form a flat ribbon, while orb web spiders use an extrusion process in which the silk dope is processed in an elongated duct to produce a cylindrical thread. This is achieved by the combination of an initial internal draw down, well inside the duct, and a final draw down, after the silk has left the spigot. The spinning mechanism in Loxosceles may be more ancestral.
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912
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Abstract
Liquid crystal elastomers (LCEs) have recently been described as a new class of matter. Here we review the evidence for the novel conclusion that the fibrillar collagens and the dragline silks of orb web spiders belong to this remarkable class of materials. Unlike conventional rubbers, LCEs are ordered, rather than disordered, at rest. The identification of these biopolymers as LCEs may have a predictive value. It may explain how collagens and spider dragline silks are assembled. It may provide a detailed explanation for their mechanical properties, accounting for the variation between different members of the collagen family and between the draglines in different spider species. It may provide a basis for the design of biomimetic collagen and dragline silk analogues by genetic engineering, peptide- or classical polymer synthesis. Biological LCEs may exhibit a range of exotic properties already identified in other members of this remarkable class of materials. In this paper, the possibility that other transversely banded fibrillar proteins are also LCEs is discussed.
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Affiliation(s)
- David P Knight
- Zoology Department, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
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913
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Nakazawa Y, Asakura T. High-Resolution 13C CP/MAS NMR Study on Structure and Structural Transition of Antheraea pernyi Silk Fibroin Containing Poly(l-alanine) and Gly-Rich Regions. Macromolecules 2002. [DOI: 10.1021/ma011999t] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yasumoto Nakazawa
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Tetsuo Asakura
- Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
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914
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Active control of spider silk strength: comparison of drag line spun on vertical and horizontal surfaces. POLYMER 2002. [DOI: 10.1016/s0032-3861(01)00713-3] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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915
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Lazaris A, Arcidiacono S, Huang Y, Zhou JF, Duguay F, Chretien N, Welsh EA, Soares JW, Karatzas CN. Spider silk fibers spun from soluble recombinant silk produced in mammalian cells. Science 2002; 295:472-6. [PMID: 11799236 DOI: 10.1126/science.1065780] [Citation(s) in RCA: 383] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Spider silks are protein-based "biopolymer" filaments or threads secreted by specialized epithelial cells as concentrated soluble precursors of highly repetitive primary sequences. Spider dragline silk is a flexible, lightweight fiber of extraordinary strength and toughness comparable to that of synthetic high-performance fibers. We sought to "biomimic" the process of spider silk production by expressing in mammalian cells the dragline silk genes (ADF-3/MaSpII and MaSpI) of two spider species. We produced soluble recombinant (rc)-dragline silk proteins with molecular masses of 60 to 140 kilodaltons. We demonstrated the wet spinning of silk monofilaments spun from a concentrated aqueous solution of soluble rc-spider silk protein (ADF-3; 60 kilodaltons) under modest shear and coagulation conditions. The spun fibers were water insoluble with a fine diameter (10 to 40 micrometers) and exhibited toughness and modulus values comparable to those of native dragline silks but with lower tenacity. Dope solutions with rc-silk protein concentrations >20% and postspinning draw were necessary to achieve improved mechanical properties of the spun fibers. Fiber properties correlated with finer fiber diameter and increased birefringence.
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Affiliation(s)
- Anthoula Lazaris
- Nexia Biotechnologies, Vaudreuil-Dorion, Quebec J7V 8P5, Canada.
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916
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Arcidiacono S, Mello CM, Butler M, Welsh E, Soares JW, Allen A, Ziegler D, Laue T, Chase S. Aqueous Processing and Fiber Spinning of Recombinant Spider Silks. Macromolecules 2002. [DOI: 10.1021/ma011471o] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Steven Arcidiacono
- US Army Soldier Biological Chemical Command, Natick Soldier Center, Kansas Street, Natick, Massachusetts 01760; Microbiotix, Inc., One Innovation Drive, Worcester, Massachusetts 01605; and Department of Biochemistry and Molecular Biology, University of New Hampshire, 46 College Road, Durham, New Hampshire 03824
| | - Charlene M. Mello
- US Army Soldier Biological Chemical Command, Natick Soldier Center, Kansas Street, Natick, Massachusetts 01760; Microbiotix, Inc., One Innovation Drive, Worcester, Massachusetts 01605; and Department of Biochemistry and Molecular Biology, University of New Hampshire, 46 College Road, Durham, New Hampshire 03824
| | - Michelle Butler
- US Army Soldier Biological Chemical Command, Natick Soldier Center, Kansas Street, Natick, Massachusetts 01760; Microbiotix, Inc., One Innovation Drive, Worcester, Massachusetts 01605; and Department of Biochemistry and Molecular Biology, University of New Hampshire, 46 College Road, Durham, New Hampshire 03824
| | - Elizabeth Welsh
- US Army Soldier Biological Chemical Command, Natick Soldier Center, Kansas Street, Natick, Massachusetts 01760; Microbiotix, Inc., One Innovation Drive, Worcester, Massachusetts 01605; and Department of Biochemistry and Molecular Biology, University of New Hampshire, 46 College Road, Durham, New Hampshire 03824
| | - Jason W. Soares
- US Army Soldier Biological Chemical Command, Natick Soldier Center, Kansas Street, Natick, Massachusetts 01760; Microbiotix, Inc., One Innovation Drive, Worcester, Massachusetts 01605; and Department of Biochemistry and Molecular Biology, University of New Hampshire, 46 College Road, Durham, New Hampshire 03824
| | - Alfred Allen
- US Army Soldier Biological Chemical Command, Natick Soldier Center, Kansas Street, Natick, Massachusetts 01760; Microbiotix, Inc., One Innovation Drive, Worcester, Massachusetts 01605; and Department of Biochemistry and Molecular Biology, University of New Hampshire, 46 College Road, Durham, New Hampshire 03824
| | - David Ziegler
- US Army Soldier Biological Chemical Command, Natick Soldier Center, Kansas Street, Natick, Massachusetts 01760; Microbiotix, Inc., One Innovation Drive, Worcester, Massachusetts 01605; and Department of Biochemistry and Molecular Biology, University of New Hampshire, 46 College Road, Durham, New Hampshire 03824
| | - Thomas Laue
- US Army Soldier Biological Chemical Command, Natick Soldier Center, Kansas Street, Natick, Massachusetts 01760; Microbiotix, Inc., One Innovation Drive, Worcester, Massachusetts 01605; and Department of Biochemistry and Molecular Biology, University of New Hampshire, 46 College Road, Durham, New Hampshire 03824
| | - Susan Chase
- US Army Soldier Biological Chemical Command, Natick Soldier Center, Kansas Street, Natick, Massachusetts 01760; Microbiotix, Inc., One Innovation Drive, Worcester, Massachusetts 01605; and Department of Biochemistry and Molecular Biology, University of New Hampshire, 46 College Road, Durham, New Hampshire 03824
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917
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Moon M, Tillinghast EK. Fine structure of the glandular epithelium during secretory silk production in the black widow spiderlatrodectus mactans. ACTA ACUST UNITED AC 2002. [DOI: 10.1080/12265071.2002.9647672] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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918
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Li G, Zhou P, Shao Z, Xie X, Chen X, Wang H, Chunyu L, Yu T. The natural silk spinning process. A nucleation-dependent aggregation mechanism? EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:6600-6. [PMID: 11737214 DOI: 10.1046/j.0014-2956.2001.02614.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The spinning mechanism of natural silk has been an open issue. In this study, both the conformation transition from random coil to beta sheet and the beta sheet aggregation growth of silk fibroin are identified in the B. mori regenerated silk fibroin aqueous solution by circular dichroism (CD) spectroscopy. A nucleation-dependent aggregation mechanism, similar to that found in prion protein, amyloid beta (Abeta) protein, and alpha-synuclein protein with the conformation transition from a soluble protein to a neurotoxic, insoluble beta sheet containing aggregate, is a novel suggestion for the silk spinning process. We present evidence that two steps are involved in this mechanism: (a) nucleation, a rate-limiting step involving the conversion of the soluble random coil to insoluble beta sheet and subsequently a series of thermodynamically unfavorable association of beta sheet unit, i.e. the formation of a nucleus or seed; (b) once the nucleus forms, further growth of the beta sheet unit becomes thermodynamically favorable, resulting a rapid extension of beta sheet aggregation. The aggregation growth follows a first order kinetic process with respect to the random coil fibroin concentration. The increase of temperature accelerates the beta sheet aggregation growth if the beta sheet seed is introduced into the random coil fibroin solution. This work enhances our understanding of the natural silk spinning process in vivo.
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Affiliation(s)
- G Li
- The Key Laboratory of Molecular Engineering of Polymers, Ministry of Education, Macromolecular Science Department, Shanghai, China
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919
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Vollrath F, Madsen B, Shao Z. The effect of spinning conditions on the mechanics of a spider's dragline silk. Proc Biol Sci 2001; 268:2339-46. [PMID: 11703874 PMCID: PMC1088885 DOI: 10.1098/rspb.2001.1590] [Citation(s) in RCA: 177] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We studied the mechanical properties of dragline threads of the edible golden silk spider Nephila edulis that are produced under spinning speeds ranging from 0.1 to 400 mm s(-1) and temperatures ranging from 5 to 40 degrees C. These conditions affected the silk in all of the mechanical traits we tested (strain at breaking, breaking energy, initial Young's modulus and point of yielding). We argue that both trade-offs (between mechanical properties) and constraints (in the manufacturing process) have a large role in defining spider silk fibres.
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Affiliation(s)
- F Vollrath
- Department of Zoology, Universitetsparken B135, 8000 Aarhus C, Denmark.
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920
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921
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Metzler DE, Metzler CM, Sauke DJ. Ribosomes and the Synthesis of Proteins. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50032-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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