Department of Physics, University of Warwick, Coventry, CV4 7AL, UK.
Phys Chem Chem Phys. 2010 Jul 14;12(26):6970-83. doi: 10.1039/c001290d. Epub 2010 May 18.
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.
二糖是高分辨率（1）H 固态 NMR 的一个具有挑战性的案例，因为 24 个独特的质子（14 个脂肪族和 10 个 OH）具有（1）H 化学位移，所有这些化学位移都落在大约 3 到 7 ppm 的狭窄范围内。本文介绍了β-麦芽糖一水合物的高分辨率（1）H（500 MHz）双量子（DQ）组合旋转和多脉冲序列（CRAMPS）固态 NMR 谱。（1）H-（1）H DQ-SQ CRAMPS 谱与使用新脉冲序列获得的（1）H（DQ）-（13）C 相关谱一起呈现，该脉冲序列使用重新聚焦的 INEPT 脉冲序列元素通过单键（13）C-（1）H J 耦合将高分辨率（1）H DQ 维度与（13）C 单量子（SQ）维度相关联，从而实现了对（1）H DQ 维度的相关。与在 30 kHz 魔角旋转（MAS）下记录的（1）H DQ 谱中仅观察到单个宽峰相比，在（1）H DQ CRAMPS 实验中使用 DUMBO（1）H 同核去耦允许分辨出不同的 DQ 相关峰，这些峰与基于 GIPAW（格点包含投影增强波）平面波赝势方法的第一性原理化学位移计算相结合，能够将（1）H 共振分配给 24 个不同的质子。我们相信这是首次通过实验确定简单糖的羟基 OH（1）H 化学位移的固态 NMR 测定。变温（1）H-（1）H DQ CRAMPS 谱表明，当温度从 348 K 降低到 248 K 时，OH 共振的（1）H 化学位移略有增加。
