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

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