High-resolution H-1 and H-1-C-13 magic angle spinning NMR spectroscopy of rat liver

High-resolution magic angle spinning (MAS) H-1 NMR spectra of small samples (ca. 8 mg) of intact rat liver are reported for the first time. One dimens ional spectra reveal a number of large well-resolved NMR signals mainly fro m low to medium molecular weight compounds (generally <1000 Daltons) from a variety of chemical classes. A range of 2D MAS-NMR experiments were perfor med, including H-1 J-resolved (JRES),H-1-H-1 total correlation spectroscopy (TOCSY) and H-1-C-13 heteronuclear multiple quantum coherence (HMQC) to en able detailed signal assignment. Resonances were assigned from alpha- and b eta-glucose, glycerol, alanine, glutamate, glycine, dimethylglycine, lysine , and threonine, together with phosphocholine, choline, lactate, trimethyla mine-N-oxide (TMAO), and certain fatty acids. Well-resolved H-1 NMR signals from glycogen (poly 1-4 alpha-glucose) were observed directly in intact li ver using MAS-NMR spectroscopy. In addition, the resonances from the glycog en (CH)-H-1 proton in alpha(1 --> 4) linked glucose units with either alpha (1 --> 4) units adjacent or alpha(1 --> 6) linked branches could be resolve d in a high-resolution H-1 NMR experiment giving direct in situ information on the ratio of alpha(1 --> 4) to alpha(1 --> 6) units. This indicates tha t despite the relatively high MW(>1,000,000 Daltons) there is considerable segmental motion in the glycogen molecules giving long H-1 T-2 relaxation t imes. Magn Reson Med 44:201-207, 2000. (C) 2000 Wiley-Liss, Inc.