Double-quantum filtered Na NMR and MRI: Selective detection of ordered sodium in an inhomogeneous B field.

Double-quantum filtered Na NMR experiments with one or two "magic angle" (54.7°) pulses in the filter step are widely used for selective observation of sodium ions that are interacting with ordered biological structures ("ordered sodium") and hence exhibit a distribution of quadrupolar splittings in their NMR spectrum. This approach has recently been extended to Na MRI where the conventional experiment has been modified, omitting the 180° pulse to reduce the absorption of radiofrequency energy during human studies.

Towards shorter composite 180° refocusing pulses for NMR.

Novel composite 180° pulses are designed for use in nuclear magnetic resonance (NMR) and verified experimentally using solution-state H NMR spectroscopy. Rather than being constructed from 180° pulses (as in much recent work), the new composite pulses are constructed from 90° pulses, with the aim of finding sequences that are shorter overall than existing equivalents. The primary (but not exclusive) focus is on composite pulses that are dual compensated - simultaneously broadband with respect to both inhomogeneity of the radiofrequency field and resonance offset - and have antisymmetric phase schemes, such that they can be used to form spin echoes without the introduction of a phase error.

Biexponential = 3/2 Spin-Lattice Relaxation in the Solid State: Multiple-Quantum Li NMR as a Probe of Fast Ion Dynamics.

Spin-lattice relaxation measurements are used in Li NMR studies of materials of potential use in solid-state Li-ion batteries as a probe of ion mobility on a fast (nanosecond to picosecond) time scale. The relaxation behavior is often analyzed by assuming exponential behavior or, equivalently, a single time constant. However, the spin-lattice relaxation of spin = 3/2 nuclei, such as Li, is in general biexponential; this is a fundamental property of = 3/2 nuclei and unrelated to any compartmentalization within the solid.

Two-dimensional H and H-detected NMR study of a heterogeneous biocatalyst using fast MAS at high magnetic fields.

Nuclear magnetic resonance (NMR) is a powerful tool for investigating atomic-scale structure in heterogeneous or composite materials where long-range order is absent. In this work solid-state H and H-detected NMR experiments were performed with fast magic angle spinning (ν = 75 kHz) and at high magnetic fields (B = 20 T) and used to gain structural insight into a heterogeneous biocatalyst consisting of an enzyme, human carbonic anhydrase II (hCA II), covalently immobilized on epoxy-functionalized silica. Two-dimensional H-H NOESY-type correlation experiments were able to provide information on H environments in silica, epoxy-silica and the immobilized enzyme.

A high-resolution natural abundance S MAS NMR study of the cementitious mineral ettringite.

Despite the widespread occurrence of sulfur in both natural and man-made materials, the S nucleus has only rarely been utilised in solid-state NMR spectroscopy on account of its very low natural abundance (0.76%), low NMR frequency (ν = 30.7 MHz at B = 9.