Complete H-1 resonance assignment of beta-maltose from H-1-H-1 DQ-SQ CRAMPS and H-1 (DQ-DUMBO)-C-13 SQ refocused INEPT 2D solid-state NMR spectra and first principles GIPAW calculations

Webber, Amy L. and Elena, Benedicte and Griffin, John M. and Yates, Jonathan R. and Pham, Tran N. and Mauri, Francesco and Pickard, Chris J. and Gil, Ana M. and Stein, Robin and Lesage, Anne and Emsley, Lyndon and Brown, Steven P. (2010) Complete H-1 resonance assignment of beta-maltose from H-1-H-1 DQ-SQ CRAMPS and H-1 (DQ-DUMBO)-C-13 SQ refocused INEPT 2D solid-state NMR spectra and first principles GIPAW calculations. Physical Chemistry Chemical Physics, 12 (26). pp. 6970-6983. ISSN 1463-9076

Abstract

A disaccharide is a challenging case for high-resolution H-1 solid-state NMR because of the 24 distinct protons (14 aliphatic and 10 OH) having H-1 chemical shifts that all fall within a narrow range of approximately 3 to 7 ppm. High-resolution H-1 (500 MHz) double-quantum (DQ) combined rotation and multiple pulse sequence (CRAMPS) solid-state NMR spectra of beta-maltose monohydrate are presented. H-1-H-1 DQ-SQ CRAMPS spectra are presented together with H-1 (DQ)-C-13 correlation spectra obtained with a new pulse sequence that correlates a high-resolution H-1 DQ dimension with a C-13 single quantum (SQ) dimension using the refocused INEPT pulse-sequence element to transfer magnetization via one-bond C-13-H-1 J couplings. Compared to the observation of only a single broad peak in a H-1 DQ spectrum recorded at 30 kHz magic-angle spinning (MAS), the use of DUMBO H-1 homonuclear decoupling in the H-1 DQ CRAMPS experiment allows the resolution of distinct DQ correlation peaks which, in combination with first-principles chemical shift calculations based on the GIPAW (Gauge Including Projector Augmented Waves) plane-wave pseudopotential approach, enables the assignment of the H-1 resonances to the 24 distinct protons. We believe this to be the first experimental solid-state NMR determination of the hydroxyl OH H-1 chemical shifts for a simple sugar. Variable-temperature H-1-H-1 DQ CRAMPS spectra reveal small increases in the H-1 chemical shifts of the OH resonances upon decreasing the temperature from 348 K to 248 K.