Molecular and Nanostructural Mechanisms of Deformation, Strength and Toughness of Spider Silk Fibrils

Nova, Andrea; Keten, Sinan; Pugno, Nicola; Redaelli, Alberto; Buehler, Markus J.

doi:10.1021/nl101341w

Cited by 355 publications

(329 citation statements)

References 52 publications

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“…Failure comes in as hydrogen bonds break in the crystalline regions, which triggers the sliding of beta-sheet strands. This coherent interaction among different domains 31 within the silk protein results in a nonlinear constituent behavior of silk comparable to experimental studies 32 of silk threads, achieving high strengths from the stiff crystal components, and improved extensibility and toughness resultant from constituents of the amorphous region.…”

Section: Molecular Structure and Mechanics Of Silksupporting

confidence: 54%

“…Molecular unfolding mechanism of the protein nanocomposite and associated nanomechanical and structural properties as a function of increasing end-to-end length. 20,31 (a) Qualification of the four-stage deformation mechanism of a single silk repeat unit. Initially (i), the protein nanocomposite consists of coiled semi-amorphous domains exhibiting hidden length embedding a stiff beta-sheet crystal.…”

Section: Molecular Structure and Mechanics Of Silkmentioning

confidence: 99%

“…A key result from these studies was that the beta-sheet crystal is the key factor in defining the mechanical strength of the composite, whereas the semi-amorphous phase controls the extensibility of the material. 31 formation (increased extensibility). As the structure is further extended, beta-sheet crystals form in the amorphous domains, bearing the exerted stress.…”

Section: Molecular Structure and Mechanics Of Silkmentioning

confidence: 99%

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A Materiomics Approach to Spider Silk: Protein Molecules to Webs

Tarakanova

Buehler

2012

JOM

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The exceptional mechanical properties of hierarchical self-assembling silk biopolymers have been extensively studied experimentally and in computational investigations. A series of recent studies has been conducted to examine structure-function relationships across different length scales in silk, ranging from atomistic models of protein constituents to the spider web architecture. Silk is an exemplary natural material because its superior properties stem intrinsically from the synergistic cooperativity of hierarchically organized components, rather than from the superior properties of the building blocks themselves. It is composed of beta-sheet nanocrystals interspersed within less orderly amorphous domains, where the underlying molecular structure is dominated by weak hydrogen bonding. Protein chains are organized into fibrils, which pack together to form threads of a spider web. In this article we survey multiscale studies spanning length scales from angstroms to centimeters, from the amino acid sequence defining silk components to an atomistically derived spider web model, with the aim to bridge varying levels of hierarchy to elucidate the mechanisms by which structure at each composite level contributes to organization and material phenomena at subsequent levels. The work demonstrates that the web is a highly adapted system where both material and hierarchical structure across all length scales is critical for its functional properties.

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Section: Molecular Structure and Mechanics Of Silksupporting

confidence: 54%

Section: Molecular Structure and Mechanics Of Silkmentioning

confidence: 99%

Section: Molecular Structure and Mechanics Of Silkmentioning

confidence: 99%

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A Materiomics Approach to Spider Silk: Protein Molecules to Webs

Tarakanova

Buehler

2012

JOM

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“…33,34 The high strength of silk materials is mainly attributed to the nanoconfined crystals (4-6 nm), while the breaking elongation is mainly attributed to the unfolding amorphous region. [35][36][37] Recently, the Brillouin spectroscopy technique has been applied to the non-invasive determination of a range of elastic moduli in spider silks. 38 Whereas this method is capable of determining the elastic tensor and mechanical properties of assembled fibers, here we are focusing on the assembly of the molecular structure.…”

Section: Silk Structure After Spinningmentioning

confidence: 99%

Secondary Structure Transition and Critical Stress for a Model of Spider Silk Assembly

2016

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Spiders spin their silk from an aqueous solution to a solid fiber in ambient conditions. However, to date the assembly mechanism in the spider silk gland has not been satisfactorily explained. In this paper, we use molecular dynamics simulations to model N. clavipes MaSp1 dragline silk formation under shear flow and determine the secondary structure transitions leading to the experimentally observed fiber structures. While no experiments are performed on the silk fiber itself, insights from this polypeptide model can be transferred to the fiber scale. The novelty of this study lies in the calculation of the shear stress (300-700 MPa) required for fiber formation and identification of the amino acid residues involved in the transition. This is the first time that the shear stress has been quantified in connection with a secondary structure transition. By study of molecules containing varying numbers of contiguous MaSp1 repeats we identified the smallest molecule size that gives rise to a 'silk-like' structure contains six poly-alanine repeats.Through a probability analysis of the secondary structure we identify specific amino acids that transition from α-helix to β-sheet. In addition to portions of the poly-alanine section these amino acids include glycine, leucine and glutamine. Stability of β-sheet structures appears to arise from a close proximity in space of helices in the initial spidroin state. Our results are in agreement with the forces exerted by spiders in the silking process and the experimentally determined global secondary structure of spidroin and pulled MaSp1 silk. Our study emphasizes the role of shear in the assembly process of silk and can guide the design of microfluidic devices that attempt to mimic the natural spinning process and predict molecular requirements for the next generation of silk-based functional materials.

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“…The device is placed on a glass substrate (1). A solvent droplet fills the microfluidic network in the device by capillary action (2).…”

Section: Reproducing Positioning and Orientationmentioning

confidence: 99%

Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms

2016

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Shape-changing materials open an entirely new solution space for a wide range of disciplines: from architecture that responds to the environment and medical devices that unpack inside the body, to passive sensors and novel robotic actuators. While synthetic shape-changing materials are still in their infancy, studies of biological morphing materials have revealed key paradigms and features which underlie efficient natural shape-change. Here, we review some of these insights and how they have been, or may be, translated to artificial solutions. We focus on soft matter due to its prevalence in nature, compatibility with users and potential for novel design. Initially, we review examples of natural shape-changing materials-skeletal muscle, tendons and plant tissues-and compare with synthetic examples with similar methods of operation. Stimuli to motion are outlined in general principle, with examples of their use and potential in manufactured systems. Anisotropy is identified as a crucial element in directing shape-change to fulfil designed tasks, and some manufacturing routes to its achievement are highlighted. We conclude with potential directions for future work, including the simultaneous development of materials and manufacturing techniques and the hierarchical combination of effects at multiple length scales.

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Molecular and Nanostructural Mechanisms of Deformation, Strength and Toughness of Spider Silk Fibrils

Cited by 355 publications

References 52 publications

A Materiomics Approach to Spider Silk: Protein Molecules to Webs

A Materiomics Approach to Spider Silk: Protein Molecules to Webs

Secondary Structure Transition and Critical Stress for a Model of Spider Silk Assembly

Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms

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