| Determination of Molecular Structures of Condensed Tannins from Plant Tissues Using HPLC-UV Combined with Thiolysis and MALDI-TOF Mass Spectrometry
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Author:
Date:
2016-10-20
[Abstract] Condensed tannins extracted from plant tissues are suitable substitutes for phenolic resins. Their molecular structure, which might influence their chemical reactivity, can be assessed by the use of both HPLC-UV after acid thiolysis and MALDI-TOF mass spectrometry. Thiolysis of plant extracts in acidic methanol with cysteamine hydrochloride results in the release of the monomeric units of the condensed tannin oligomers that can be further quantified by reversed-phase HPLC-UV by comparison with analytical standards. MALDI-TOF mass spectrometry using 2,5-dihydroxybenzoic acid as matrix and K+ ...
[摘要] 从植物组织提取的缩合单宁是酚醛树脂的合适替代物。它们的可能影响它们的化学反应性的分子结构可以通过在酸硫解和MALDI-TOF质谱之后使用HPLC-UV来评估。用半胱胺盐酸盐在酸性甲醇中溶解植物提取物导致缩合的单宁寡聚体的单体单元的释放，其可以通过与分析标准比较通过反相HPLC-UV进一步定量。使用2,5-二羟基苯甲酸作为基质和K sup +作为阳离子化试剂的MALDI-TOF质谱分析突出了单宁的分子结构特征（例如单体单元序列）低聚物。该方法允许估计平均和最大（可观察）聚合度，单体单元的类型和单宁单体的糖基化和/或酯化的存在。
[背景] 缩合单宁是由可从几种植物组织（例如软木树皮）中提取的黄烷-3-醇单体单元组成的多酚低聚物。它们已被认为是树脂配方（例如木材粘合剂和泡沫材料）中合成酚醛树脂的合适替代品。在缩合鞣酸中检测到的最常见的黄烷-3-醇单体，其羟基化模式和立体化学不同，如图1所示。
![]() "src ="/attached/image/20161012/20161012024340_4416.jpg"/>
图1.在缩合单宁结构中确定的最常见的单体
低聚物中单体单元的具体结构和聚合度强烈影响单宁的化学反应性和物理性质，例如与醛的缩合反应速率，重金属螯合能力和水溶液的粘度溶液（Pizzi和Stephanou，1994; ...
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| In situ Digestion of Wheat Cell-wall Polysaccharides
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Author:
Date:
2014-12-05
[Abstract] Cell walls of the wheat endosperm are mostly composed of arabinoxylans (AX) and mixed (1→3), (1→4)-β-glucans (BG) (Saulnier et al., 2012). Here, we present an optimized protocol to degrade enzymatically these cell-wall polysaccharides into oligosaccharides, directly from wheat grain cross sections. The main difficulty is to provide a sufficient amount of humidity for the enzyme to be active, while the amount of liquid at the surface of the tissue should stay low to prevent any delocalization of the released products. With this protocol, enzymatic degradation was shown to be efficient ...
[摘要] 小麦胚乳的细胞壁主要由阿拉伯木聚糖（AX）和混合的（1→3），（1→4）-β-葡聚糖（BG）组成（Saulnier等人，2012）。在这里，我们提出一个优化的协议，以酶法将这些细胞壁多糖降解为低聚糖，直接从小麦籽粒横截面。主要的困难是提供足够量的湿度以使酶活性，而组织表面处的液体量应保持低以防止释放的产物的任何离域。使用该方案，酶降解显示是有效的，并且释放的寡糖的离域化估计低于50μm（Veličkovic等人，2014）。虽然它可以用于其他目的，但是这种原位酶消化主要用于通过基质辅助激光解吸/电离（MALDI）获得小麦胚乳的横截面的分子图像）质谱（Veličkovic等人，2014）。细胞壁多糖在结构上是异质的，表现出高质量并且缠结到复杂网络中。因此，它们不适合通过质谱法直接分析，并且它们需要作为第一步骤降解为较小的化合物。在该方案中，还描述了对应于MALDI基质的沉积的另外的步骤。
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| In vitro Assay of the Glycosyltransferase Activity of a Heterologously Expressed Plant Protein
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Author:
Date:
2014-11-05
[Abstract] Glycosyltransferases are carbohydrate active enzymes containing catalytic modules involved in catalysing the biosynthesis of glycosidic bonds in oligo- and polysaccharides and glycoconjugates. One of the most comprehensive collections of Carbohydrate Active enZYmes is the CAZy database (http://www.cazy.org) comprising 120,000 glycosyltransferases allocated to 96 families based mainly on sequence homologies of their conserved and catalytically active domains (Cantarel et al., 2009). Interestingly, the glycosyltransferase activities of ...
[摘要] 糖基转移酶是含有催化模块的碳水化合物活性酶，其涉及催化寡糖和多糖和糖缀合物中糖苷键的生物合成。 Carbohydrate Active enZYmes最全面的集合之一是CAZy数据库（ http://www.cazy.org ） ），其包含分配给96个家族的120,000个糖基转移酶，主要基于其保守和催化活性结构域的序列同源性（Cantarel等人，2009）。有趣的是，仅约1.6％的这些蛋白质的糖基转移酶活性已经通过实验表征（Lombard等人，2014）。近年来，已显示许多家族的膜结合糖基转移酶在植物细胞壁多糖的生物合成中起关键作用（Doblin等人，2010; Scheller和Ulvskov，2010 ; ...
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