Two-dimensional (43)Ca-(1)H correlation solid-state NMR spectroscopy

Solid State Nucl Magn Reson. 2009 Feb;35(1):32-6. doi: 10.1016/j.ssnmr.2008.11.002. Epub 2008 Nov 24.

Abstract

Calcium-43 (nuclear spin, S=7/2) is an NMR insensitive low-gamma quadrupolar nucleus and up until recently only one-dimensional solid-state (43)Ca NMR spectra have been reported. Through-space correlation experiments are challenging between spin-12 and low-gamma quadrupolar nuclei because of the intrinsically weak dipolar interaction and the often-low natural abundance of the quadrupolar nucleus. Rotary-resonance recoupling (R(3)) has recently been used to re-introduce hetero-nuclear dipolar interactions for sensitive high-gamma quadrupolar nuclei, but has not yet been applied in the case of low-gamma half-integer quadrupolar nuclei. Here an effective and robust 2D (1)H-(43)Ca NMR correlation experiment combining the R(3) dipole-recoupling scheme with 2D HMQC is presented. It is demonstrated that the weak (43)Ca-(1)H dipolar coupling in hydroxyapatite and oxy-hydroxyapatite can be readily re-introduced and that this recoupling scheme is more efficient than conventional cross-polarization transfer. Moreover, three (43)Ca-(1)H dipolar coupled calcium environments are clearly resolved in the structurally unknown oxy-hydroxyapatite. This local information is not readily available from other techniques such as powder XRD and high resolution electron microscopy. R(3)-HMQC is also a desirable experiment because the set-up is simple and it can be applied using conventional multi-resonance probes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms*
  • Calcium Isotopes / analysis*
  • Calcium Isotopes / chemistry
  • Durapatite / chemistry*
  • Magnetic Resonance Spectroscopy / methods*
  • Protons
  • Sensitivity and Specificity
  • Spin Labels

Substances

  • Calcium Isotopes
  • Protons
  • Spin Labels
  • Durapatite