Chitosans are a family of binary co-polymers of glucosamine and N-acetylglucosamine residues with superb material properties and versatile biological functionalities. Structurally, they are characterised by three parameters, namely the degree of polymerisation (DP), fraction of acetylation (F_A), and pattern of acetylation (PA). Both the physico-chemical properties and the biological activities of chitosans are influenced by these structural parameters. Moreover, chitosan samples are invariably mixtures of molecules differing in these properties so that the values determined for DP and F_A are mean values. Consequently, to fully describe a chitosan polymer sample, determination of the dispersities Đ for both DP and F_A need to be included, too, but the likely influence of these parameters on properties and bioactivities of chitosans is still mostly ignored. In this review, we summarise the state of the art concerning the production and analysis of defined chitosan polymers as well as our current knowledge on the structure-function relationships of their properties and bioactivities. Progress in this field was mostly driven by the availability of increasingly sensitive analytical techniques, such as HPSEC-RID-MALLS for determination of DP and Đ_DP, and NMR for determination of F_A and PA. More recently, capillary electrophoresis has been suggested for the analysis of Đ_FA, and enzymatic-mass spectrometric fingerprinting methods are revolutionizing F_A and PA analyses. Heterogeneous and homogeneous chemical methods of partial de-N-acetylation of chitin and partial N-acetylation of polyglucosamine yield chitosans with known F_A, but yet unknown Đ_FA, while different chemical and physical methods of partial depolymerisation yield chitosans with known DP and Đ_DP. Today, the availability of increasing numbers of well-defined recombinant chitin deacetylases is beginning to give access to chitosan polymers with different non-random PA. In the recent past, this has allowed systematic investigations of the influence of DP and F_A on material properties and biological activities, it currently allows us to begin investigating the roles of Đ_DP and PA, and it will hopefully soon enable us to also study the role of Đ_FA.

壳聚糖是葡糖胺和N-乙酰葡糖胺残基的二元共聚物家族，具有优异的材料性能和通用的生物学功能。在结构上，它们是由三个参数，聚合即度（DP），乙酰化的级分（其特征在于˚F_甲）和（PA）的乙酰化的图案。这些结构参数影响壳聚糖的理化性质和生物学活性。此外，壳聚糖样品始终是这些性质不同的分子的混合物，因此确定的DP和F _A值为平均值。因此，为了全面描述壳聚糖聚合物样品，需要确定分散度Đ两个DP和˚F_一个需要被包括在内，太多，但在性能和壳聚糖的生物活性，这些参数的可能影响仍然主要被忽略。在这篇综述中，我们总结了有关确定的壳聚糖聚合物生产和分析的最新技术，以及我们目前对它们的性能和生物活性之间的结构-功能关系的认识。在这一领域的进步主要是受的越来越敏感的分析技术，如HPSEC-RID-MALLS测定DP和可用性从动Đ _DP，和NMR测定的˚F_甲和PA。最近，毛细管电泳一直建议的分析Đ _FA，和酶促质谱法指纹图谱正在彻底改变F _A和PA分析。异构和部分去的均匀的化学方法Ñ甲壳质和局部的-acetylation Ñ与已知的聚葡糖胺产量的脱乙酰壳多糖-acetylation ˚F_甲，但仍然未知的Đ _FA，而不同的化学和已知DP和部分解聚产量壳聚糖的物理方法Đ _DP。如今，越来越多的定义明确的重组几丁质脱乙酰酶的可用性开始使人们能够使用具有不同非随机PA的壳聚糖聚合物。最近一段时间以来，这已经允许DP和影响的系统研究˚F_一个对材料性能和生物活性，它目前可以让我们开始调查的角色Đ _DP和PA，并有望很快使我们也研究作用Đ _FA。