Sodium ions in ordered environments in biological systems: Analysis of Na-23 NMR spectra

Experiments that selectively excite I = 3/2 nuclei exhibiting residual quad rupolar splittings are used to acquire Na-23 NMR spectra from a range of bi ologically relevant samples containing sodium in ordered environments. Thre e complementary approaches to the analysis of such spectra are described: ( i) measurement of relaxation rates, (ii) extraction of homogeneous linewidt hs from two-dimensional Jeener-Broekaert spectra, and (iii) simultaneous fi tting of detailed theoretical functions to a series of one-dimensional Jeen er-Broekaert spectra, Analysis of relaxation rates provides evidence for co mpartmentation in bovine nasal cartilage. Each approach is used to demonstr ate the presence of anisotropy in transverse relaxation in porcine tendon, For certain samples containing collagen, a good theoretical fit to the spec tra was obtained using a model that allows for anisotropic relaxation by in cluding the effects of slow lateral and radial diffusion. (C) 1999 Academic Press.