Deuterium nuclear spin-lattice relaxation times and quadrupolar coupling constants in isotopically labeled saccharides

C-13 and H-2 spin-lattice relaxation times have been determined by inversion recovery in a range of site-specific C-13- and H-2-labeled saccharides under identical solution conditions, and the data were used to calculate deuterium nuclear quadrupolar coupling constants (H-2 NQCC) at specific sites within cyclic and acyclic forms in solution. C-13 T-1 values ranged from similar to 0.6 to 8.2 s, and H-2 T-1 values ranged from similar to 79 to 450 ms, depending on molecular structure (0.4 M sugar in 5 mM EDTA (disodium salt) in (H2O)-H-2-depleted H2O, pH 4.8, 30 degrees C). In addition to providing new information on C-13 and H-2 relaxation behavior of saccharides in solution, the resulting (2)H1 NQCC values reveal a dependency on anomeric configuration within aldopyranose rings, whereas H-2 NQCC values at other ring sites appear less sensitive to configuration at C1. In contrast, H-2 NQCC values at both anomeric and nonanomeric sites within aldofuranose rings appear to be influenced by anomeric configuration. These experimental observations were confirmed by density functional theory (DFT) calculations of H-2 NQCC values in model aldopyranosyl and aldofuranosyl rings. (C) 2000 Academic Press.