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  • 學位論文

使用訊號加強標誌於醣類分子之質譜研究

Mass Spectrometric Analysis of Carbohydrate Molecules with Signal Enhancing Tags

指導教授 : 方俊民

摘要


醣分子是最常見且最具結構變異性的天然物,並且在生物體中支配著許多重要的生理功能。然而由於結構及組成的複雜度,嚴重阻礙了醣類領域的研究。在許多分析醣類的方法中,質譜法能針對醣分子進行精確、高靈敏度且快速的結構分析。但由於天然醣分子在質譜儀中的游離效率不佳,因此常藉由化學修飾幫助提升醣類在質譜中的偵測效率。 透過我們實驗室最近開發出的方法,以碘為氧化劑,還原性醣與胺類可藉由形成醯胺鍵結直接建立醣類偶合體。因此我們利用此氧化醯胺法來偶合寡醣與芳香烷基胺及含有精胺酸或苯基丙胺酸的胜肽。首先用一系列的胺類來修飾麥芽三醣(maltotriose, G3),並進行快速篩選醣類衍生物在介質輔助雷射脫附游離及電灑游離質譜中的訊號增強表現。篩選出的訊加強標誌亦可應用於修飾麥芽七醣(maltoheptaose, G7),以更進一步研究透過醣類衍生化所提升的質譜偵測效能。本研究結果指出,這些修飾訊號加強標誌的醣類分子的確可有效的增進醣類在質譜儀中的偵測靈敏度,尤其在介質輔助雷射脫附游離質譜法中,訊號增強效果特別明顯 (高達100 倍)。 另一方面,在碘/醋酸的條件下,利用新設計的二胺化合物以縮合法修飾G7 和唾液酸四聚體 (tetrasialic acid, SA4)。此二胺化合物含有精胺酸的基團,而這種修飾方法皆可將醛醣以及酮酸進行衍生化,並且有效的在介質輔助雷射脫附游離及電灑游離質譜中增強醣類分子的偵測訊號。唾液酸四聚體在此反應條件下,同時進行內脂化作用,因此其衍生物的質譜訊號增加450 倍以上。

關鍵字

醣類 衍生化 訊號增強 質譜

並列摘要


Carbohydrates are the most abundant and structurally diverse natural products.They possess a large number of functionalities in biology. Nevertheless, their structural complexities hamper the detailed understanding of their roles. Mass spectrometry has been proved to be a precise, high sensitive and fast tool for carbohydrates structural analysis. Due to the low ionization efficiency of carbohydrates, derivatization has frequently used to improve the detection efficiency of oligosaccharides in mass spectrometry. Recently, a direct conjugation method by forming a robust amide bond between amines and the reducing end of aldose was developed by our laboratory. Therefore, we utilized this oxidative amidation process for derivitizing oligosaccharide with aralkylamine and peptides containing arginine or phenylalanine moieties. Initially, maltotriose (G3) was modified with various amine tags for a rapid screening of their effects in amplification of the signal intensity in MALDI– and ESI–MS. The chosen signal enhancing tags were subsequently used to modify maltoheptaose (G7) for further sensitivity studies. Our results showed that these oligosaccharide derivatives indeed enhanced the detection sensitivity in mass spectrometry, particularly up to 100-fold enhancement in MALDI-MS. On the other hand, tagging G7 or tetrasialic acid (SA4) with a new designed diamine tag through the iodine-promoted oxdative condensation was conducted. This diamine tag contained an arginine moiety, and this derivatization method was useful for not only aldoses but also ketoacids to show significant signal enhancement in both ESI–and MALDI–MS. Under the reaction conditions, tetrasialic acid also underwent intramolecular lactonization to give a derivative that exhibit more than 450-fold signal enhancement in MALDI–MS.

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