Solid State NMR update, Feb 2007 issue

Solid State Nuclear Magnetic Resonance
Volume 31, Issue 1 , February 2007, Pages 1-9
doi:10.1016/j.ssnmr.2006.09.002
Comparison of high-resolution solid-state NMR MQMAS and STMAS methods for half-integer quadrupolar nuclei
Julien Trebosc a, Jean-Paul Amoureux a, and Zhehong Gan b
a UCCS, CNRS-8181, University of Lille-1, C7-ENSCL, 59652 Villeneuve d’Ascq, France
b NHMFL, 32310 Tallahassee, FL, USA
Received 15 May 2006; revised 18 September 2006. Available online 28 September 2006.

Abstract

Several different amplitude-modulated two-dimensional high-resolution methods, based on MQMAS and STMAS, are compared. They include 3QMAS, 5QMAS, DQ-STMAS, and DQF-STMAS experiments. A new method, called t1-split-STMAS, is also proposed for spin-3/2 nuclei. The comparison is performed in terms of isotropic resolution and spectral-width, efficiency, and sensitivity to magic-angle offset and spinning speed fluctuations.

Solid State Nuclear Magnetic Resonance
Volume 31, Issue 1 , February 2007, Pages 55-61
doi:10.1016/j.ssnmr.2007.01.001
Double-quantum filtered heteronuclear correlation spectroscopy under magic angle spinning
Yao-Hung Tseng a, Yi-Ling Tsai a, Tim W.T . Tsai a, Chun-Pin Lin a, b, Shih-Hao Huang a, b, Chung-Yuan Mou a, c and Jerry C.C. Chan a, Corresponding Author Contact Information, E-mail The Corresponding Author
a Department of Chemistry, National Taiwan University, 1, Section 4, Roosevelt Road, Taipei, Taiwan
b Graduate Institute of Clinical Dentistry, National Taiwan University, Taipei
c Center of Condensed Matter, National Taiwan University, Taipei, Taiwan
Received 30 September 2006; revised 29 December 2006. Available online 8 January 2007.


Abstract

We present a simple experimental method to extract the van Vleck second moment of a multiple-spin system under high-resolution condition. The idea is to incorporate a double-quantum (DQ) filter into the pulse sequence of heteronuclear correlation spectroscopy so that a DQ excitation profile can be obtained by measuring a series of 2D spectra. The effects of spinning frequency and proton decoupling are demonstrated on the measurements of two model compounds, viz. hydroxyapatite and brushite. Based on the results obtained for the model compounds, the P-31 homonuclear second moment of the apatite component in rat dentin is characterized. The method is generally suited for the study of bone, enamel and dentin.

Keywords: Brushite; Calcium phosphate; HAp; NMR; Double-quantum filter; HETCOR; Second moment; Dentin; Teeth