Two-dimensional magic angle spinning NMR investigation of naturally occurring chitins: Precise 1H and 13C resonance assignment of α- and β-chitin

✍ Scribed by Hiroyuki Kono

• Publisher: Wiley (John Wiley & Sons)
• Year: 2004
• Tongue: English
• Weight: 135 KB
• Volume: 75
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.20124

✦ Synopsis

Abstract

^13^C homonuclear through‐bond correlations of α‐ and β‐chitin were determined by using two‐dimensional (2D) INADEQUATE spectra of these allomorphs purified from crab shell and squid pen, respectively. The 2D ^13^C–^13^C correlation spectra where two directly bonded carbons share a common double‐quantum frequency (DQ) enabled us to precisely assign all ^13^C resonances of the chitin allomorphs for the first time. Following the complete ^13^C assignment, ^1^H chemical shifts of protons attached to each carbon nuclei were assigned by 2D frequency‐switched Lee–Goldberg (FSLG) ^1^H–^13^C heteronuclear correlation (HETCOR) spectra of the chitin allomorphs, recorded with a short mixing time (60 μs) to provide isotropic ^1^H–^13^C chemical shift correlations between bonded pairs proton and carbon nuclei. From the ^13^C and ^1^H chemical shifts of chitin allomorphs, all 2‐deoxy‐2‐acetamide‐D‐glucose (N‐acetyl‐D‐glucosamine) monomer units in each allomorph were revealed to be an identical ^13^C–^13^C backbone conformation and magnetically equivalent. In addition, it was strongly suggested that there are two different hydrogen‐bonding patterns at the hydroxyl groups of α‐chitin by comparing ^1^H chemical shifts at the C6 site of α‐chitin with those at the same site of β‐chitin. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004