Conventional mass spectrometry (MS)-based analytical methods for small carbohydrate fragments (oligosaccharides, degree of polymerization 2-12) are time-consuming due to the need for an offline sample pretreatment such as desalting. Herein, we report a new paper spray ionization method, named desalting paper spray (DPS), which employs a piece of triangular filter paper for both sample desalting and ionization. Unlike regular paper spray ionization (PSI) and nanoelectrospray ionization (nanoESI), DPS-MS allows fast and sensitive detection of oligosaccharides in biological samples having complex matrices (e.g., Tris, PBS, HEPES buffers, or urine). When an oligosaccharide sample is loaded onto the filter paper substrate (10 × 5 mm, height × base) made mostly of cellulose, oligosaccharides are adsorbed on the paper via hydrophilic interactions with cellulose. Salts and buffers can be washed away using an ACN/H2O (90/10 v/v) solution, while oligosaccharides can be eluted from the paper using a solution of ACN/H2O/formic acid (FA) (10/90/1 v/v/v) and directly spray-ionized from the tip of the paper. Various saccharides at trace levels (e.g., 50 fmol) in nonvolatile buffer can be quickly analyzed by DPS-MS (<5 min per sample). DPS-MS is also applicable for direct detection of oligosaccharides from glycosyltransferase (GT) reactions, a challenging task that typically requires a radioactive assay. Quantitative analysis of acceptor and product oligosaccharides shows increased product with increased GT enzymes used for the reaction, a result in line with the radioactivity assay. This work suggests that DPS-MS has potential for rapid oligosaccharide analysis from biological samples.

中文翻译：

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使用脱盐纸喷雾质谱 (DPS-MS) 快速、灵敏地检测寡糖。

由于需要脱盐等离线样品预处理，传统的基于质谱 (MS) 的小碳水化合物片段（寡糖，聚合度 2-12）分析方法非常耗时。在此，我们报告了一种新的纸喷雾电离方法，称为脱盐纸喷雾（DPS），它采用一张三角形滤纸进行样品脱盐和电离。与常规纸喷雾电离 (PSI) 和纳米电喷雾电离 (nanoESI) 不同，DPS-MS 可以快速灵敏地检测具有复杂基质的生物样品（例如 Tris、PBS、HEPES 缓冲液或尿液）中的寡糖。当将低聚糖样品加载到主要由纤维素制成的滤纸基材（10 × 5 mm，高 × 底）上时，低聚糖通过与纤维素的亲水相互作用吸附在纸上。盐和缓冲液可以使用 ACN/H2O (90/10 v/v) 溶液洗掉，而低聚糖可以使用 ACN/H2O/甲酸 (FA) (10/90/1 v) 溶液从纸上洗脱/v/v) 并直接从纸尖喷射电离。DPS-MS 可以快速分析非挥发性缓冲液中痕量水平（例如 50 fmol）的各种糖类（每个样品 <5 分钟）。DPS-MS 也适用于从糖基转移酶 (GT) 反应中直接检测寡糖，这是一项通常需要放射性测定的挑战性任务。受体和产物寡糖的定量分析表明，随着用于反应的 GT 酶增加，产物增加，结果与放射性测定一致。