Silk structure studied with nuclear magnetic resonance Tetsuo Asakura a,⇑ , Yu Suzuki a , Yasumoto Nakazawa a , Koji Yazawa a , Gregory P. Holland b , Jeffery L. Yarger b a Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan b Department of Chemistry & Biochemistry, Magnetic Resonance Research Center, Arizona State University, Tempe, AZ 85287-1604, USA Edited by J. Feeney and J.W. Emsley article info Article history: Received 16 April 2012 Accepted 13 August 2012 Available online 29 September 2012 Keywords: Silk fibroin NMR Bombyx mori S. c. ricini A. Pernyi Anaphe Polyalanine Poly(Ala-Gly) Spider silk abstract Ó 2012 Elsevier B.V. All rights reserved. Contents 1. Introduction .......................................................................................................... 24 2. NMR methods used for silk study ......................................................................................... 24 2.1. 13 C CP-MAS, Static CP and DD-MAS NMR ............................................................................. 25 2.2. DARR .......................................................................................................... 27 2.3. WISE........................................................................................................... 29 2.4. HETCOR ........................................................................................................ 30 2.5. Spin diffusion.................................................................................................... 30 2.6. Double quantum–single quantum (DQ/SQ) 2D NMR .................................................................... 31 2.7. DECODER ....................................................................................................... 33 2.8. REDOR ......................................................................................................... 33 2.9. HR-MAS ........................................................................................................ 34 3. Structure of B. mori silk fibroin ........................................................................................... 35 3.1. Silk I ........................................................................................................... 35 3.2. Silk II .......................................................................................................... 37 3.3. Structural change from Silk I to Silk II ................................................................................ 39 0079-6565/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.pnmrs.2012.08.001 Abbreviations: CP-MAS, cross polarization magic angle spinning; DD-MAS, dipolar decoupling magic angle spinning; CSA, chemical shift anisotropy; DARR, 13 C– 13 C correlation spectra with dipolar assisted rotational resonance; WISE, 1 H– 13 C wideline separation; HETCOR, heteronuclear correlation; TPPM, two pulse phase modulation; CRAMPS, combined rotation and multiple pulse spectroscopy; FSLG, frequency-switched Lee-Goldburg; DQ/SQ, double-quantum/single-quantum; INADEQUATE, incredible natural abundance double quantum transfer experiment; DOQSY, double quantum spectroscopy; DECODER, direction exchange with correlation for orientation-distribution evaluation and reconstruction; REDOR, rotational-echo double resonance; HR-MAS, high-resolution magic angle spinning; HSQC, heteronuclear single quantum correlation; INEPT, insensitive nuclei enhanced by polarization; MD, molecular dynamics; MM, molecular mechanics; Silk I, state of silk fibroin before spinning; Silk II, state of silk fibroin after spinning; MaSp1, dragline silk spidroin 1; MaSp2, dragline silk spidroin 2. ⇑ Corresponding author. Fax: +81 423837733. E-mail address: asakura@cc.tuat.ac.jp (T. Asakura). Progress in Nuclear Magnetic Resonance Spectroscopy 69 (2013) 23–68 Contents lists available at SciVerse ScienceDirect Progress in Nuclear Magnetic Resonance Spectroscopy journal homepage: www.elsevier.com/locate/pnmrs