NMR Spectroscopy and Imaging of Sodium in Ordered Environments. The Return of the Central Transition

✍ Scribed by Colan E. Hughes; Richard Kemp-Harper; Peter Styles; Stephen Wimperis

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 160 KB
• Volume: 111
• Category: Article
• ISSN: 1064-1866
• DOI: 10.1006/jmrb.1996.0081

✦ Synopsis

Recent 23 Na NMR studies have shown that sodium ions ordered sodium ions. Owing to the absence of inhomogeneous quadrupolar broadening and the relative inefficiency exhibiting residual quadrupolar splittings occur in a wide variety of human and animal tissues, including brain (1, 2), of the homogeneous broadening, this central transition is muscle (2), cartilage (3-7), and blood (8-10). The splitusually quite narrow. Therefore, these new experiments can tings seem to arise as a result of the ions interacting with be used to provide much greater sensitivity in 23 Na NMR ''structural'' biomolecules, such as the collagen fibers in spectroscopy and acceptable resolution in 23 Na NMR imconnective tissues and the various phospholipids and proaging of ordered sodium ions. teins that constitute cell membranes. Although still mobile, Any NMR technique that filters the 23 Na spins through a these ''ordered'' sodium ions therefore reside in a molecular state described purely by second-rank spherical tensor operaenvironment which can be considered as either ''solid'' or tors, T 2, p , is suitable for selective observation of ordered ''liquid crystalline'' in the NMR sense.

sodium ions (11). The coherence order p can take any al-It is important to be able to distinguish between ordered lowed value. For example, the DQF experiment with 54.7Њ sodium ions and the possibly much greater number of ions flip angles filters the spins through a state of in-phase doublethat are in a purely liquid-like environment and so do not quantum coherence, described by a combination of the tenexhibit quadrupolar splittings. This can be achieved using sors T 2,02 and T 2,/2 , while the Jeener-Broekaert experiment 23 Na NMR techniques that yield a singly antiphase spectrum, filters through a state of quadrupolar order, T 2,0 . The final i.e., one where the Ém I Å 3 2 … to Ém I Å 1 2 … and Ém I Å 0 1 2 … to observable state produced by both these experiments is pure second-rank single-quantum coherence, T 2,01 , from which, Ém I Å 0 3 2 … ''satellite'' transitions of the I Å 3