Substituent distribution in carboxymethl glucans: development of a quantitative method for the determination of the substituent distribution along and over the polymer chains

多糖衍生物是一种复杂的混合物，除了相对分子质量外，还会随着取代基程度和分布的不同而变化。后者必须在不同的、相关的层次结构水平上考虑(在葡萄糖基单元中，沿着多糖链，以及在多糖链上)。虽然对于非离子纤维素醚已经开发和改进了各种水平的取代模式的有效方法，但对于阴离子羧甲基醚还没有这样的方法。这种聚电解质的性质(例如，水的溶解度)与取代基分布之间的关系尚未完全了解，因为后者不能详细描述，而仅限于平均值。羧甲基化也被应用于淀粉、葡聚糖和半纤维素等其他多糖中，并引发了同样的问题。因此，本项目的目标是根据多年在多糖衍生物取代基模式分析领域的经验，开发一种有效的测定羧甲基葡聚糖(CMG)中CM-分布的方法。为了获得正确的CM基团模式，必须从聚合物分子制备具有代表性的低聚序列混合物，并且对于每个DP，必须定量地确定取代基轮廓。考虑到所有数据，将齐聚物轮廓与随机模型进行比较，并将轮廓与DP的轮廓变化进行比较，应能够得出关于异质性(DS梯度、双峰分布)的结论。在前期工作的基础上，建立了LC-MS联用方法。必要的是适当的样品制备和对所有步骤的控制，以区分效果。具体地说，应研究和制定下列里程碑：材料崩解，部分解聚动力学研究和随机性控制，衍生和标记策略，分离和质谱学方法的发展(LC-ESI-MS，MALDI-TOF-MS)，定量评估和模型计算；所制定的方法应应用于具有相同取代度但不同性质的各种CMG。此外，多步解聚标记策略应允许区分二阶和一阶异质性。

Polysaccharide derivatives are complex mixtures which beside molecular weight vary with respect to the degree and distribution of substituents. The latter has to be considered on various, related hierarchical structure levels (in the glucosyl unit, along the polysaccharide chain, and over the polysaccharide chains). While for nonionic cellulose ethers powerful methods for the various levels of substitution patterns have been developed and improved, no such methods exist for the anionic carboxymethyl ethers.Carboxymethyl cellulose (CMC) is the most abundant cellulose derivative. The relationship between the properties (e.g. water solubility) of this polyelectrolyte and the substituent distribution are not fully understood, since the latter cannot be described in detail, but is restricted to average values. Carboxymethylation is also applied to other polysaccharides like starch, dextran and hemicelluloses and raises the same questions.Therefore, it is the aim of the project, based on long-year experience in the field of the analysis of substituent patterns of polysaccharide derivatives, to develop a powerful method for the determination of the CM-distribution in carboxymethyl glucans (CMG). To obtain correct patterns of CM groups, representative mixtures of oligomeric sequences must be prepared from the polymer molecules, and for each DP, the substituent profiles must be determined quantitatively.Taking all data into account, the comparison of the oligomer profiles with the random model, and the change of the profiles with DP, shall allow to draw conclusions on heterogeneities (DS gradient, bimodal distributions). Based on the preliminary work, an LC-MS method shall be worked out. Essential is an appropriate sample preparation and control of all steps with respect to discriminating effects. Concretely, the following milestones shall be investigated and worked out: disintegration of the material, kinetic studies of partial depolymerization and control of randomness, derivatisation- and labeling strategies, development of separation and mass spectrometric methods (LC-ESI-MS, MALDI-ToF-MS), quantitative evaluation and model calculations; methods worked out shall be applied to various CMG with the same DS but different properties.Furthermore, a multiple-step depolymerization-labeling strategy shall allow to differentiate heterogeneities of second and first order.