title: Complete (1)H resonance assignment of beta-maltose from (1)H-(1)H DQ-SQ CRAMPS and (1)H (DQ-DUMBO)-(13)C SQ refocused INEPT 2D solid-state NMR spectra and first principles GIPAW calculations.
abstract: A disaccharide is a challenging case for high-resolution (1)H solid-state NMR because of the 24 distinct protons (14 aliphatic and 10 OH) having (1)H chemical shifts that all fall within a narrow range of approximately 3 to 7 ppm. High-resolution (1)H (500 MHz) double-quantum (DQ) combined rotation and multiple pulse sequence (CRAMPS) solid-state NMR spectra of beta-maltose monohydrate are presented. (1)H-(1)H DQ-SQ CRAMPS spectra are presented together with (1)H (DQ)-(13)C correlation spectra obtained with a new pulse sequence that correlates a high-resolution (1)H DQ dimension with a (13)C single quantum (SQ) dimension using the refocused INEPT pulse-sequence element to transfer magnetization via one-bond (13)C-(1)H J couplings. Compared to the observation of only a single broad peak in a (1)H DQ spectrum recorded at 30 kHz magic-angle spinning (MAS), the use of DUMBO (1)H homonuclear decoupling in the (1)H 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 (1)H resonances to the 24 distinct protons. We believe this to be the first experimental solid-state NMR determination of the hydroxyl OH (1)H chemical shifts for a simple sugar. Variable-temperature (1)H-(1)H DQ CRAMPS spectra reveal small increases in the (1)H chemical shifts of the OH resonances upon decreasing the temperature from 348 K to 248 K.
authors.affiliation: Department of Physics, University of Warwick, Coventry, CV4 7AL, UK.
authors.forename: Amy L
authors.initials: AL
authors.lastname: Webber
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Elena
authors.forename: John M
authors.initials: JM
authors.lastname: Griffin
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Yates
authors.forename: Tran N
authors.initials: TN
authors.lastname: Pham
authors.forename: Francesco
authors.initials: F
authors.lastname: Mauri
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Pickard
authors.forename: Ana M
authors.initials: AM
authors.lastname: Gil
authors.forename: Robin
authors.initials: R
authors.lastname: Stein
authors.forename: Anne
authors.initials: A
authors.lastname: Lesage
authors.forename: Lyndon
authors.initials: L
authors.lastname: Emsley
authors.forename: Steven P
authors.initials: SP
authors.lastname: Brown