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Supporting information

DNP NMR Spectroscopy Reveals New Structures, Residues and Interactions in Wild Silks

Hamish C. Craiga, Sean J. Blamires*a, Marc-Antoine Sani,b Michael Kasumovic,aAditya Rawal,c and James M. Hook*c,d

a School of Biological, Earth and Environmental Science, University of , NSW, 2052 b School of Chemistry, Bio21 Institute, University of Melbourne, Parkville, Victoria, 3010 c Mark Wainwright Analytical Centre, and

d School of Chemistry, University of New South Wales, , Australia, 2052

Figure S1: Schematic molecular model of spider MaSp2 silk showing the major structural regions: amorphous (blue) and crystalline (red), incorporating the proposed new structural findings. a R145 conformation of Arginine seen within L. hasseltii in proposed conformation assisting stabilisation of the amorphous region as a part of the b-spiral. b Difference in the length of hydrogen bonding seen between the interior (A)n region and surface (AG)n of crystallites within silk of N. plumipes. c Hydroxyproline and its added hydrogen bonding site taking the place of proline in the type II b turn responsible for the formation the b-spiral within the amorphous region of A. keyserlingi and L. hasseltii silk.

Table S1. High Sensitivity Advanced Amino Acid Mass Spectrometry (AAA-MS) results showing the average relative mole percentage of the major amino acids within each silk. (NB: different silk samples collected at tandem were used for this purpose to preserve the original samples used for DNP NMR analysis and to prevent any influence of the added AMUPol)

* Hydroxyproline and Cysteic Acid co-elute in the High Sensitivity AAA-MS, approximately 60% of presented values are attributed to Hydroxyproline

Figure S2. Expansions and assignments of the 1H-13C HETCOR experiments showing 1D 13C and 1H slices taken through the cross correlation peaks of interest (“Hydroxyproline“ from A. keyserlingi and “NH downfield shifts“ from N. plumipes). δH and δC in top left corners represent the point (in ppm) at which the 1D slices where extracted, where a projected sum was provided within the NH Downfield shifts

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Figure S3. Expansion and assignment of 1H-13C HETCOR experiments: carbonyl shifts from N. plumipes showing 1D 13C and 1H spectra taken through each major cross correlation peak. Deconvolution was provided for potentially ambiguous overlapping peaks where necessary, deconvoluted peaks provided in black, with the simulated projection presented in red.

Figure S4. Expansion and assignment of DNP enhanced 15N CP MAS spectra from Figure 1; the arrow indicates the upfield shift of Arginine Ne peak.

Figure S5. Demonstration R145 H-bonding structure of Arginine within the silk of L. hasselti, with the NH1,2 forming both a weak H-bond (left) and ionic bidentate bonds (right).

Methods

Materials

Silk samples were collected from wild caught individuals from three species of spider: Latrodectus hasselti, keyserlingi, and Nephila plumipes. We varied the number of individual silked to reach the following sample weights. For Latrodectus hasseltii we collected 12 mg of silk from one individual; for Argiope keyserlingi we collected 14 mg from two individuals; for Nephila plumipes we collected 18 mg from three individuals. Individual A. keyserlingi and N. plumipes were collected in the field in , and silked in a makeshift laboratory upon collection; A. keyserlingi and L. hasseltii were collected around Sydney, NSW, and silked at the University of New South Wales, Sydney, upon collection. All spiders were silked using procedures outlined by Blamires et al. (2016)[1].

2 H2O (D2O) and 1,1,2,2-tetrachloroethane (TCE) were purchased from Sigma-Aldrich (Castle Hill, Australia), AMUPol and TEKPol were purchased from Cortecnet (Voisins-Le-Bretonneux, France).

Sample Preparation

Each silk sample was wetted in an Eppendorf tube with equivalent volume of 10 mM AMUPol (D2O/H2O 80:20 solution) at a 1:1 mass ratio (ie 14 mg of silk to 14uL of AMUPol solution) for 10 mins then transferred to a 3.2 mm sapphire rotor with a silicon plug and a zirconia spinning cap. The process was repeated with 10 mM TEKPol in TCE, however with 36 uL being added to 18 mg of Nephila silk for comparison. Part of the TCE solution was absorbed into the silk as indicated by visible sample swelling. The treated was packed as above into a 3.2 mm sapphire rotor with a silicon plug and a zirconia spinning cap.

Dynamic Nuclear Polarization Enhanced 13C and 15N Cross Polarization MAS (DNP CP MAS) Solid-State NMR Spectroscopy

DNP NMR measurements were performed on a 400 MHz (9.4 T) Bruker AVANCE-III-DNP system (Germany) equipped with a 263 GHz gyrotron and a triple resonance 3.2 mm low temperature Magic Angle Spinning (MAS) probe. DNP was achieved by irradiating the sample with 130 mA microwaves matching the AMUPol electron frequency[2]. The samples were inserted into the probe and spun to MAS rates of 8 kHz (± 3Hz) with sample temperature set at 110 K used for all experiments, except if indicated in the figure caption.

DNP-enhanced 13C and 15N CP MAS were performed with 102 kHz 1H excitation, followed by a 1H linear amplitude ramp (50% to 100%) of cross-polarization scheme with 1.5 ms contact time and 102 kHz SPINAL-64 decoupling during acquisition[3]. The RF amplitudes for 13C and 15N were 59.5 kHz and 44.6 kHz, respectively. A recycle delay of 10 s was chosen as ca. 3 x 1 13 T1( H) which was obtained indirectly from saturation-recovery C CP MAS experiments. 64 scans were accumulated for the 1D experiments using 25 Hz and 80 Hz line broadening for 13C and 15N spectra, respectively. The microwave-off acquisitions for 13C CP MAS were performed under identical conditions.

DNP-enhanced 1H-13C and 1H-15N 2D correlation (HETCOR) experiments were acquired using similar CP conditions. The frequency-shifted Lee-Goldberg (FSLG) scheme was used for 1H homonuclear decoupling during the indirect evolution time with an RF field amplitude of 102 kHz. States-TPPI detection was used and a scaling factor of 0.56 was applied to correct for 1H 13 chemical shift scaling. C HETCOR were obtained with 256 t1 increments of 62.5 μs with 2 15 scans accumulated and N HETCOR were obtained with 126 t1 increments of 62.5 μs with 8 scans accumulated. The 2D spectra were processed with a 4k by 1k complex point matrix using 100 Hz of line broadening.

13C DNP enhancement factors (εDNP) were determined by scaling the intensities of the spectrum without and with MW irradiation.

AMUPol versus TEKPol

The DNP gain obtained using aqueous AMUPol was greater than obtained with TEKPol in tetrachlorethane (TCE). This is likely due to the difference in solvent absorption by the spider silk., which is known to readily absorb water and is an important aspect of the property of supercontraction[5], implying a better distribution of AMUPol in the samples. Despite some swelling observed when the silk was treated with a solution of TEKPOL in TCE, the 13C CPMAS signal enhancement was limited to TCE (Fig. S6) indicating a poor radical distribution around the silk structure.

Figure S6. 13C CP MAS spectra of N. plumipes silk using TEKPol as the radical source. Microwave off (red line) and microwave on (blue line) showed that 13C signals of the spider silk are poorly enhanced (εDNP = 1.3) compared to the organic solvent TCE (εDNP = 60). The experiments were performed at 110K under 8 kHz MAS spinning speed.

References

[1] S. J. Blamires, M. M. Kasumovic, I. M. Tso, P. J. Martens, J. M. Hook, A. Rawal, International Journal of Molecular Sciences 2016, 17, 1294. [2] S. Claire, R. Melanie, C. Gilles, A. Fabien, W. R. T., O. Olivier, T. Paul, Angewandte Chemie Int. Edn 2013, 125, 11058-11061. [3] S. R. Hartmann, E. L. Hahn, Physical Review 1962, 128, 2042-2053. [4] G. Metz, X. L. Wu, S. O. Smith, Journal of Magnetic Resonance, Series A 1994, 110, 219-227. [5] J.D. van Beek, J. Kummerlen, F. Vollrath, B.H. Meier, Int. J. Biologic. Macromol. 1999, 24, 173–178