Scrutinizing the datasets obtained from nanoscale features of spider silk fibres

Abstract

Spider silk fibres share unprecedented structural and mechanical properties which span from the macroscale to nanoscale and beyond. This is possible due to the molecular features of modular proteins termed spidroins. Thus, the investigation of the organizational scaffolds observed for spidroins in spider silk fibres is of paramount importance for reverse bioengineering. This dataset consists in describing a rational screening procedure to identify the nanoscale features of spider silk fibres. Using atomic force microscopy operated in multiple acquisition modes, we evaluated silk fibres from nine spider species. Here we present the complete results of the analyses and decrypted a number of novel features that could even rank the silk fibres according to desired mechanostructural features. This dataset will allow other researchers to select the most appropriate models for synthetic biology and also lead to better understanding of spider silk fibres extraordinary performance that is comparable to the best manmade materials.

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OPEN

SUBJECT CATEGORIES

Atomic force microscopy

Applications of AFM

Biomaterials

Nanoscale biophysics

Received: 01 April 2014

Accepted: 19 September 2014

Published: 14 October 2014

Scrutinizing the datasets obtained from nanoscale features of spider silk bres

Luciano P. Silva1 & Elibio L. Rech1

Spider silk bres share unprecedented structural and mechanical properties which span from the macroscale to nanoscale and beyond. This is possible due to the molecular features of modular proteins termed spidroins. Thus, the investigation of the organizational scaffolds observed for spidroins in spider silk bres is of paramount importance for reverse bioengineering. This dataset consists in describing a rational screening procedure to identify the nanoscale features of spider silk bres. Using atomic force microscopy operated in multiple acquisition modes, we evaluated silk bres from nine spider species. Here we present the complete results of the analyses and decrypted a number of novel features that could even rank the silk bres according to desired mechanostructural features. This dataset will allow other researchers to select the most appropriate models for synthetic biology and also lead to better understanding of spider silk bres extraordinary performance that is comparable to the best manmade materials.

Design Type(s) in vitro design species comparison design

Measurement Type(s) nanoscale phenomena

Technology Type(s) atomic force microscopy

Factor Type(s) species molecular entity

Sample Characteristic(s)

1Embrapa Genetic Resources and Biotechnology, PBI, Parque Estao Biolgica Final W5 Norte, Braslia 70770-

917, DF, Brazil.

Correspondence and requests for materials should be addressed to L.P.S. (email: [email protected] or

[email protected])

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Avicularia Aglaoctenus lagotis Argiope argentata Argiope

lobata Avicularia juruensis Gasteracantha cancriformis Nephila

clavipes Nephilengys cruentata Parawixia bistriata gland

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Background & Summary

Spider silk bres represent the most impressive biological archetypes of high performance bres. This stems from the fact that spider silk bres can surprisingly merge strong tensile strength and high elasticity which are similar to those observed for steel and nylon, respectively. The last few decades have been marked by an explosion of studies describing molecular, structural, and mechanical properties of spider silk bres111. The major reason for this interest is that spider silk bres are one of the most promising next-generation candidates for bioinspired polymers12.

Among the challenges to the widespread use of spider silk bres as models for novel materials is the understanding how spider silk proteins (spidroins) interact among them to form supramolecular nanostructures in the bre13,14. This fact, together with the limited number of species represented by available molecular and mechanostructural data15, led to a demand for the development of methods and datasets organized to identify specic features reliable for synthetic biology approaches.

A systematic proposal toward a rational use of nanoscale features of spider silk bres was presented in our recent Nature Communications paper1. There, we explored the biodiversity of spider silk bres by several atomic force microscopy (AFM) imaging and spectroscopic modes. Using that method1 we and others are able to systematically select, on demand, high-performance bres for nanoengineering purposes. However, we suggested that other researchers could experience difculty in reproducing our experiments with exactly the same instrumental setup and conditions. Thus, we avoided reporting absolute quantities and instead relied on normalised values and ratios during comparisons among bres in that study1. Here we present the datasets from that study1, which would be valuable to many other researchers studying the nano- and microscale mechanostructural properties of spider silk bres.

Methods

Experimental design

We performed AFM analyses of natural silk bres from nine spider species with focus on the use of multiple operation-acquisition modes under imaging and force spectroscopic approaches. A dataset of quantitative nanoscale parameters were obtained from silk bres images and force spectroscopic data under near-native conditions (Figure 1).

Sample preparation

Spider silks were supplied by Dr Paulo C. Motta (Institute of Biology, University of Brasilia, Brazil) under IBAMA/MMA license number (0128753 BR) and Dr Randolph V. Lewis (Utah State University, USA). Silks were reeled from adult specimens of Aglaoctenus lagotis (Araneomorphae, Lycosidae), Argiope argentata (Araneomorphae, Araneidae), Argiope lobata (Araneomorphae, Araneidae), Avicularia juruensis (Mygalomorphae, Theraphosidae), Avicularia sp. (Mygalomorphae, Theraphosidae), Gasteracantha cancriformis (Araneomorphae, Araneidae), Nephila clavipes (Araneomorphae, Nephilidae), Nephilengys cruentata (Araneomorphae, Tetragnathidae), and Parawixia bistriata (Araneomorphae,

Figure 1. Representative scheme of the experimental design including AFM modes and corresponding quantitative parameters of the spider silk bres.

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Araneidae). Silk bres extruded from major ampullate gland spigots (or acinous gland spigots for Avicularia species) were rolled around a rotating tubular graphite at 5 mm/s, taking care to avoid contamination by silks that did not originate in the desired glands. Two synthetic silk bres termed Recombinant-1 (MaSp-1, 16 GGLGGQGGLGGLGSQGAGLGGYGQGGAGQGGAAAAAAAAS module, a segment from a sequence previously obtained from Parawixia bistriata16 and under GenBank accession no. ADG57596.1) and Recombinant-2 (MaSp-2, 16 GPGGYGPGQQGPGGYGPGQQGPS GPGSAAAAAAAA module, a segment from a sequence previously obtained from Nephila clavipes17 and

under Swiss-Prot accession no. P46804.1) were expressed, puried, and polymerised according to previously described methods18 and deposited on a glass coverslip. Silk bre samples were stored in a dust-free and light-protected Petri dish under ambient conditions until analysis. Commercial nylon and steel yarns were used as controls.

Multimode atomic force microscopy imaging analyses

AFM analyses were performed in contact, soft contact, force modulation, lateral force (trace-minus-retrace data), dynamic, phase imaging, and Kelvin force microscopy operation/acquisition modes on a commercial SPM-9600 (Shimadzu, Japan) with suitable probes1 in a temperature-controlled room (23 C) under atmospheric conditions. AFM scans of similar areas were acquired at a maximum resolution of 512 512 pixels and a rate of 0.51 Hz. The scanned areas were perfect squares that ranged in size from 40 m 40 m (lower magnication) to 250 nm 250 nm (higher magnication). We used four AFM off-line software packages to qualitatively and quantitatively analyse the acquired images (SPM-9600 off-line v. 3.304Shimadzu, Japan; SPIP v. 5.1.5Image Metrology, Denmark; WSxM v. 5.0 Develop3.2Nanotec Electronica, Spain; and Gwyddion v. 2.22 for WindowsCzech Metrology Institute, Czech Republic).

All the images (including all modes) were plane-tted automatically to compensate for any sample tilt due to misalignments of tip and bres using SPM-9600 off-line software. Height images were also 3D-rendered using WSxM software for visual inspection and qualitative investigation. Linear roughness amplitude, spatial, and hybrid parameters were calculated along the longitudinal extension (10 m) of ve single bres for each spider species using Gwyddion software.

Surface quantitative nanoroughness (from contact modeheight images), nanostiffness (from force modulation modephase images), nanofriction (from lateral force modehorizontal deection images), nanoviscoelasticiy (from viscoelastic modephase images), nanoamplitude (from viscoelastic modeamplitude images), and nanopotential (from Kelvin force modephase images) were obtained using Gwyddion statistical quantities tool by measuring the mean, standard error of the mean (s.e.m.) values of each parameter; and further by calculating the relative standard error of the mean values of ten to fteen images acquired at higher magnication (250 nm 250 nm) of each spider silk bre for each acquisition mode.

Single-bre force spectroscopy analyses

Force spectroscopy experiments were performed in ambient air with the same AFM-imaged bres. The approach-release curves were recorded at 23 C, 30% relative humidity, and a pulling rate of 1 Hz. Twelve force-distance curves were obtained from distinct regions in ve different bres. Data for the complete sample set were acquired with the same contact or dynamic mode tips at the same AFM acquisition setup. Static nanomechanics parameters from force-distance curves were calculated using SPIP software. Maximum load, maximum pulling, and snap in forces; detachment separation and zero indentation distances; Young modules; and energies dissipated were calculated.

Data Records

The dataset produced by this study have been deposited at gshare. Link to the data depositions are provided in the Data Citations section. The format, content and availability of the depositions are described in the following subsections and in Table 1.

Data record 1imaging and force spectroscopic data

The quantitative imaging and force spectroscopic data are contained in worksheets indicating the raw data and at the bottom of the worksheets are the calculated mean values, standard errors of the mean (s.e.m.) values, and also relative standard errors of the mean (r.s.e.m.) values (Data Citation 1). The quantitative data in gshare are organized by AFM imaging (Files 17), force spectroscopic (File 8) modes and AFM probes technical data (File 9). The column details are given bellow.

File 1. linear roughness parameters.xlsx

This data le carries three worksheets containing raw data and descriptive statistics regarding roughness (amplitude, spatial and hybrid) parameters obtained in the longitudinal direction of the spider silk bres using Gwyddion software (Windows, v. 2.22). These parameters are described in the English version of Gwyddion user guide available on-line at http://gwyddion.net/documentation/user-guide-en/ (pages 6061) and also shared in the slides of a developers talk available on-line at http://gwyddion.net/ presentations/talk-roughness-David-Necas-2012.pdf.

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Raw data (images and force curves)

Contact/Dynamic modes (height) Linear roughness All All

Contact/Dynamic modes (height) Surface roughness All AllForce modulation mode (phase) Surface nanostiffness All Representative for 4 speciesLateral force mode (deection) Surface nanofriction All Representative for 7 speciesViscoelastic mode (phase) Surface nanoviscoelasticity All AllViscoelastic mode (amplitude) Surface nanoamplitude All AllKelvin probe mode (potential) Surface nanopotential All RepresentativeForce-distance curves (contact) Static Mechanical All Representative for 8 species and manmade materials

AFM mode Measured parameters Tabulated data

(worksheets)

Table 1. Availability of measured AFM data as deposited on FigShare (Data Citation 1).

The column descriptions for the raw data worksheets are as follows:

Amplitude parameters

COLUMN ASample Label.

COLUMN BRoughness Average (Ra)Arithmetical mean deviation. The average deviation of all points roughness prole from a mean line over the evaluation length.

COLUMN CRoot mean square roughness (Rq)The average of the measured height deviations taken within the evaluation length and measured from the mean line.

COLUMN DMaximum height of the roughness (Rt)Maximum peak-to-peak-valley height. The absolute value between the highest and lowest peaks.

COLUMN EMaximum roughness valley depth (Rv)Lowest valley. There is the depth of the deepest valley in the roughness prole over the evaluation length.

COLUMN FMaximum roughness peak height (Rp)Highest peak. There is the height of the highest peak in the roughness prole over the evaluation length.

COLUMN GAverage maximum height of the roughness (Rtm)Mean peak-to-valley roughness. It is determined by the difference between the highest peak ant the lowest valley within multiple samples in the evaluation length.

COLUMN HAverage maximum roughness valley depth (Rvm)The mean valley depth based on one peak per sampling length. The single deepest valley is found in ve sampling lengths (m = 5) and then averaged. COLUMN IAverage maximum roughness peak height (Rpm)The mean peak height based on one peak per sampling length. The single highest peak is found in ve sampling lengths (m = 5) and then averaged. COLUMN JAverage third highest peak to third lowest valley height (R3z)The distance between the third highest peak and the third lowest valley. A peak is a portion of the surface above the mean line crossings. COLUMN KAverage third highest peak to third lowest valley height (R3z ISO)The height of the third highest peak from the third lowest valley per sampling length. The base roughness depth is found in ve sampling lengths and then averaged.

COLUMN LAverage maximum height of the prole (Rz)The average absolute value of the ve highest peaks and the ve lowest valleys over the evaluation length.

COLUMN MAverage maximum height of the roughness (Rz ISO)The average peak-to-valley roughness based on one peak and one valley per sampling length. The single largest deviation is found in ve sampling lengths and then averaged.

COLUMN NSkewness (Rsk)Skewness is a parameter that describes the shape of the amplitude distribution function (ADF) that is the probability function that gives the probability that a prole of the surface has a certain height z at any position x. Skewness is a simple measure of the asymmetry of the ADF, or, equivalently, it measures the symmetry of the variation of a prole about its mean line.

COLUMN OKurtosis (Rku)Kurtosis is the ADF shape parameter considered. Kurtosis relates to the uniformity of the ADF or, equivalently, to the spikiness of the prole.

COLUMN PWaviness average (Wa)A typically used number to describe waviness of the surface and that is closely related to the Ra.

COLUMN QRoot mean square waviness (Wq)The average of the measured waviness value deviations. COLUMN RWaviness maximum height (Wy = Wmax)The difference value between the highest point and the lowest point of a measurement curve.

COLUMN SMaximum height of the prole (Pt)The maximum peak to valley height of the prole in the assessment length.

Spatial parameters

COLUMN ASample Label.

COLUMN BAverage wavelength of the prole (lambda a)The average wavelength that can be calculated from average roughness (nm) and average absolute slope (degree).

COLUMN CRoot mean square (RMS) wavelength of the prole (lambda q)The average of the measured wavelength of the prole deviations.

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Hybrid parameters

COLUMN ASample LabelCOLUMN BAverage absolute slope (delta a)The average absolute slope of the prole.

COLUMN CRoot mean square (RMS) slope (delta q) (106)The average absolute slope of the prole deviations.

COLUMN DLength (L)The length of the prole.

COLUMN EDeveloped prole length (L0)

COLUMN FProle length ratio (Lr)

File 2. surface nanoroughness parameters.xlsx

This data le carries one worksheet containing raw data and descriptive statistics regarding surface roughness parameters obtained from square areas of height images (dynamic mode) of the spider silk bres using Gwyddion software (Windows, v. 2.22). These parameters are described in the English version of Gwyddion user guide available on-line at http://gwyddion.net/documentation/user-guide-en/ (pages 5354) and also shared in the slides of a developers talk available on-line at http://gwyddion.net/ presentations/talk-roughness-David-Necas-2012.pdf.

The column descriptions for the raw data worksheet are as follows:COLUMN ASample LabelCOLUMN BAverage ValueCOLUMN CMinimumCOLUMN DMaximumCOLUMN EMedianCOLUMN FRaCOLUMN GRmsCOLUMN HSkewnessCOLUMN IKurtosisCOLUMN JSurface AreaCOLUMN KProjected AreaCOLUMN LInclination (theta)

COLUMN MInclination (phi).

File 3. surface nanostiffness parameters.xlsx

This data le carries one worksheet containing raw data and descriptive statistics regarding surface stiffness parameters obtained from square areas of phase images (force modulation mode) of the spider silk bres using Gwyddion software (Windows, v. 2.22). These parameters are described in the English version of Gwyddion user guide available on-line at http://gwyddion.net/documentation/user-guide-en/ (pages 5354) and also shared in the slides of a developers talk available on-line at http://gwyddion.net/ presentations/talk-roughness-David-Necas-2012.pdf.

The column descriptions for the raw data worksheet are as follows:COLUMN ASample LabelCOLUMN BAverage ValueCOLUMN CMinimumCOLUMN DMaximumCOLUMN EMedianCOLUMN FRaCOLUMN GRmsCOLUMN HSkewnessCOLUMN IKurtosis.

File 4. surface nanofriction parameters.xlsx

This data le contains one worksheet containing raw data and descriptive statistics regarding surface frictional parameters obtained from square areas of horizontal deection images (lateral force mode) of the spider silk bres using Gwyddion software (Windows, v. 2.22). These parameters are described in the English version of Gwyddion user guide available on-line at http://gwyddion.net/documentation/user-guide-en/ (pages 5354) and also shared in the slides of a developers talk available on-line at http:// gwyddion.net/presentations/talk-roughness-David-Necas-2012.pdf.

The column descriptions for the raw data worksheet are as follows:COLUMN ASample LabelCOLUMN BAverage ValueCOLUMN CMinimumCOLUMN DMaximumCOLUMN EMedianCOLUMN FRaCOLUMN GRms.

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File 5. surface nanoviscoelasticiy parameters.xlsx

This data le contains one worksheet containing raw data and descriptive statistics regarding surface viscoelastic parameters obtained from square areas of phase images (viscoelastic-phase mode) of the spider silk bres using Gwyddion software (Windows, v. 2.22). These parameters are described in the English version of Gwyddion user guide available on-line at http://gwyddion.net/documentation/user-guide-en/ (pages 5354) and also shared in the slides of a developers talk available on-line at http:// gwyddion.net/presentations/talk-roughness-David-Necas-2012.pdf.

The column descriptions for the raw data worksheet are as follows:COLUMN ASample LabelCOLUMN BAverage ValueCOLUMN CMinimumCOLUMN DMaximumCOLUMN EMedianCOLUMN FRaCOLUMN GRmsCOLUMN HSkewnessCOLUMN IKurtosis.

File 6. surface nanoamplitude parameters.xlsx

This data le contains one worksheet containing raw data and descriptive statistics regarding surface stiffness parameters obtained from square areas of amplitude images (viscoelastic-phase mode) of the spider silk bres using Gwyddion software (Windows, v. 2.22). These parameters are described in the English version of Gwyddion user guide available on-line at http://gwyddion.net/documentation/user-guide-en/ (pages 5354) and also shared in the slides of a developers talk available on-line at http:// gwyddion.net/presentations/talk-roughness-David-Necas-2012.pdf.

The column descriptions for the raw data worksheet are as follows:COLUMN ASample LabelCOLUMN BAverage ValueCOLUMN CMinimumCOLUMN DMaximumCOLUMN EMedianCOLUMN FRaCOLUMN GRmsCOLUMN HSkewnessCOLUMN IKurtosis.

File 7. surface nanopotential parameters.xlsx

This data le contains one worksheet containing raw data and descriptive statistics regarding surface potential parameters obtained from square areas of Kelvin force microscopy images (surface potential mode) of the spider silk bres using Gwyddion software (Windows, v. 2.22). These parameters are described in the English version of Gwyddion user guide available on-line at http://gwyddion.net/ documentation/user-guide-en/ (pages 5354) and also shared in the slides of a developers talk available on-line at http://gwyddion.net/presentations/talk-roughness-David-Necas-2012.pdf.

The column descriptions for the raw data worksheet are as follows:COLUMN ASample LabelCOLUMN BRaCOLUMN CRms.

File 8. static mechanical parameters.xlsx

This data le contains one worksheet containing raw data and descriptive statistics regarding static mechanical parameters obtained from force-distance curves of the spider silk bres using SPIP software and are described in its manual.

The column descriptions for the raw data worksheet are as follows:COLUMN ASample Label.

COLUMN BMaximum Load Force (Max Ld)The maximum loading force usually at the left end of the approach curve.

COLUMN CMaximum Pulling Force (Max Pull)The maximum pulling force on the retraction curve.

COLUMN DSnap In (Snap In)The magnitude of the force immediately after snap in.

COLUMN EDetachment Separation (Detach Sep)The separation (distance between tip apex and the maximum indentation point) at detachment.

COLUMN FYoungs Modulus (Youngs Mod)The elastic modulus calculated by one of the indentation tting models on the Force versus Separation curve.

COLUMN GZero Indentation (Zero Ind)The point in the Force versus Separation graph which is used as zero point for indentation tting.

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COLUMN HDissipated Energy (Energy)The area between the approach curve and the retraction curve of the force versus separation curve.

File 9. AFM probes technical data.doc

This data le contains one table with the description of the AFM probes used to obtain the images and force curve spectra of the spider silk bres.

COLUMN 1AFM operation/acquisition mode.

COLUMN 2Cantilever type.

COLUMN 3Cantilever metal coating.

COLUMN 4Cantilever length.

COLUMN 5Cantilever resonant frequency.

COLUMN 6Cantilever spring constant.

COLUMN 7Tip type.

COLUMN 8Tip curvature radius.

COLUMN 9Tip material.

COLUMN 10Probe manufacturer/model.

File 10. linear roughness parameters.zip

This data le contains raw data AFM height mode images in ASCII format and which were used for obtain linear roughness parameters.

File 11. surface roughness parameters.zip

This data le contains raw data AFM height mode images in Shimadzu proprietary format and which were used for obtain surface roughness parameters.

File 12. surface nanostiffness parameters.zip

This data le contains raw data AFM force modulation mode (phase) images in Shimadzu proprietary format and which were used for obtain surface nanostiffness parameters.

File 13. surface nanofriction parameters.zip

This data le contains raw data AFM lateral force mode (horizontal deectiontrace and retrace) images in Shimadzu proprietary format and which were used for obtain surface nanofriction parameters.

File 14. surface nanoviscoelasticity parameters.zip

This data le contains raw data AFM viscoelastic mode (phase) images in Shimadzu proprietary format and which were used for obtain surface nanoviscoelasticity parameters.

File 15. surface nanoamplitude parameters.zip

This data le contains raw data AFM viscoelastic mode (amplitude) images in Shimadzu proprietary format and which were used for obtain surface nanoamplitude parameters.

File 16. surface nanopotential parameters.zip

This data le contains raw data AFM Kelvin probe mode (potential) images in Shimadzu proprietary format and which were used for obtain surface nanopotential parameters.

File 17. static mechanical parameters.zip

This data le contains raw data AFM force spectroscopy mode (force curves) in ASCII format and which were used for obtain static mechanical parameters.

Technical Validation

Validation of the study

The experimental design presented in this dataset has been validated in several ways. Firstly, forward (trace) and backward (retrace) scans were performed for all imaging modes as well as approach and retraction curves were performed for all force spectroscopic modes both to ensure that no distortion was occurring at any level. Secondly, the same AFM tip was used when direct comparisons were required to ensure similar tip geometry and cantilever spring constant. Finally, it has been largely demonstrated that spider silk bres show high degree of variability in their structural and mechanical properties at interspecic, intraspecic and intraindividual levels15. Thus, absolute values of the present data descriptor must be taken with careful consideration.

Usage Notes

There are several predictable uses for these datasets. Firstly, they suggest candidate spider species and consequently their silk bres for further molecular studies based on nanoscale characteristics. Secondly, it could be used to select which bres display desired mechanostructural features. Lastly, these datasets can be used to compare with nanoscale features of several other materials, including synthetic bres, plastics, metals, ceramics, glasses, papers, woods, and resins.

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References

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35843596 (2009).

3. Keten, S., Xu, Z., Ihle, B. & Buehler, M. J. Nanoconnement controls stiffness, strength and mechanical toughness of -sheet crystals in silk. Nat. Mater. 9, 359367 (2010).

4. Nova, A., Keten, S., Pugno, N. M., Redaelli, A. & Buehler, M. J. Molecular and nanostructural mechanisms of deformation, strength, and toughness of spider silk brils. Nano Lett. 10, 26262634 (2010).

5. Giesa, T., Arslan, M., Pugno, N. M. & Buehler, M. J. Nanoconnement of spider silk brils begets superior strength, extensibility, and toughness. Nano Lett. 11, 50385046 (2011).

6. Hagn, F. et al. A conserved spider silk domain acts as a molecular switch that controls bre assembly. Nature 465, 239242 (2010).

7. Askarieh, G. et al. Self-assembly of spider silk proteins is controlled by a pH-sensitive relay. Nature 465, 236238 (2010).8. Sponner, A., Unger, E., Grosse, F. & Weisshart, K. Differential polymerization of the two main protein components of dragline silk during bre spinning. Nat. Mater. 4, 772775 (2005).

9. Rousseau, M. E., Lefevre, T. & Pezolet, M. Conformation and orientation of proteins in various types of silk bers produced by Nephila clavipes spiders. Biomacromolecules 10, 29452953 (2009).

10. Menezes, G. M., Teul, F., Lewis, R. V., Silva, L. P. & Rech, E. L. Nanoscale investigations of synthetic spider silk bers modied by physical and chemical processes. Polym. J. 45, 9971006 (2013).

11. Cranford, S. W., Tarakanova, A., Pugno, N. M. & Buehler, M. J. Nonlinear material behaviour of spider silk yields robust webs. Nature 482, 7276 (2012).

12. Omenetto, F. G. & Kaplan, D. L. New opportunities for an ancient material. Science 329, 528531 (2010).13. Keten, S. & Buehler, M. J. Nanostructure and molecular mechanics of spider dragline silk protein assemblies. J. R. Soc. Interface 7, 17091721 (2010).

14. Sponner, A. et al. Composition and hierarchical organisation of a spider silk. PLoS One 2, e998 (2007).15. Madsen, B., Shao, Z. Z. & Vollrath, F. Variability in the mechanical properties of spider silks on three levels: interspecic, intraspecic and intraindividual. Int. J. Biol. Macromol. 24, 301306 (1999).

16. Rech, E. L. et al. Proteins from the webs of Nephilengys cruentata, Avicularia juruensis and Parawixia bistriata spiders isolated from Brazilian biodiversity. Patent US20100311645 (2010).

17. Hinman, M. B. & Lewis, R. V. Isolation of a clone encoding a second dragline silk broin. J. Biol. Chem. 267, 1932019324 (1992).18. Teul, F. et al. A protocol for the production of recombinant spider silk-like proteins for articial ber spinning. Nat. Protoc. 4, 341355 (2009).

Data Citation

1. Silva, L. P. & Rech, E.. Figshare http://dx.doi.org/10.6084/m9.gshare.978888 (2014).

Acknowledgements

L.P.S. and E.L.R. acknowledges nancial support from Embrapa, MCT/CNPq (processes no. 555175/2005-7, 302018/2008-5, 305637/2011-8, 563802/2010-3, and 480286/2012-4), FAPDF (process no. 193.000.561-2009) and CAPES (process no. 23038.019088/2009-58). We thank Dr Paulo C. Motta (Institute of Biology, University of Brasilia, Brazil) and Dr Randolph V. Lewis (Department of Molecular Biology, University of Wyoming, USA) for spider silks and fruitful discussions.

Author Contributions

L.P.S. and E.L.R designed the experiments. E.L.R. conceptualised and directed the research project. L.P.S. performed the AFM imaging and force spectroscopy. L.P.S. analysed the data, organized the datasets, and wrote the paper. Both authors discussed the results and commented on the manuscript.

Additional information

Competing nancial interests: The authors declare no competing nancial interests.

How to cite this article: Silva, L. P. and Rech, E. L. Scrutinizing the datasets obtained from nanoscale features of spider silk bres. Sci. Data 1:140040 doi: 10.1038/sdata.2014.40 (2014).

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Metadata associated with this Data Descriptor is available at http://www.nature.com/sdata/ and is released under the CC0 waiver to maximize reuse.

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