固態核磁共振在糖類分子上分析應用

Solid-state NMR characterization of monosaccharides

鄒德里(Der-Lii M. Tzou)

《化學》 63卷2期 (2005/06) Pp. 185-192

https://doi.org/10.6623/chem.2005014

摘要

固態核磁共振針對碳水化合物的殊碳糖異構物α-和β-form分別進行一維磁化轉移/魔角自旋(CP/MAS)和二維碳-13/氮-15異核相關(Heteronuclear correlation)實驗分析，一維碳-13磁化轉移魔角自旋光譜上，殊碳糖異構中心(anomeric center)在90 ppm附近出現兩個相距約3-5 ppm的共振頻率，這兩個共振頻率被指認為是由異構物α-和β-form產生，除此之外我們並根據它們的魔角自旋旋轉邊峰推測分別推算出各別化學位移各方向異性(Chemical shift anisotropy)，比較α-和β-form化學位移張量之主軸值軸，其中前者較後者具軸對稱性。由兩者不對稱參數之比值和兩者出現數量比率(population ratio)在半對數作圖可發現明顯相依性。再者，含氨基的殊碳糖異構中心在二維碳-13/氮-15異核相關圖譜，可藉由碳-13化學位移提高氮-15的分辨率，結果顯示α-和β-form的共振頻率約差1-2 ppm。固態核磁共振提供一簡單且直接技術檢測單糖體殊碳糖異構物。

關鍵字

碳水化合物 ； 殊碳糖異構物 ； 化學位移同向性 ； 異核相關實驗 ； 化學位移異向性

並列摘要

Solid-state NMR analysis of the anomeric center in carbohydrates was performed by 1D ^(13)C cross-polarization/magic-angle spinning (CP/MAS) and 2D ^(13)C/^(15)N heteronuclear correlation experiments. In the 1D ^(13)C CP/MAS spectrum, the anomeric center C-1 of these carbohydrates revealed two well resolved resonances shifted by 3-5 ppm, which were readily assigned to the anomeric α and β forms. Additionally, we extracted the ^(13)C chemical shift anisotropy (CSA) tensor elements of the two forms from their spinning sideband intensities, respectively. The chemical shift tensor for the α anomer was more axially symmetrical than that of the β form. A strong linear correlation was obtained when the ratio of the axial asymmetry of the ^(13)C chemical shift tensors of the two anomeric forms was plotted in a semi-logarithmic plot against the relative population of the two anomers. Furthermore, the ^(15)N resonances of the α and β anomers of amino monosaccharides with specifically ^(13)C-1/^(15)N labeling were resolved by simple 2D ^(13)C/^(15)N heteronuclear correlation spectroscopy where the α and β resonances shifted apart by 1-2 ppm in the extended ^(15)N dimension. It is demonstrated that solid-state NMR spectroscopy is a simple and powerful technique to characterize the anomeric effect of monosaccharides.

並列關鍵字

carbohydrates ； anomers ； isotropic chemical shift ； heteronuclear correlation spectroscopy ； chemical shift anisotropy