Moraxella catarrhalis (M. catarrhalis) is a pathogenic gram-negative bacterium that causes otitis media and sinusitis in children. Three major serotypes A, B and C are identified to account for approximately 95% of the clinical isolates. Understanding the conformational properties of different serotypes of M. catarrhalis provides insights into antigenic determinants. In this work, all-atom molecular dynamics simulations were conducted for M. catarrhalis lipooligosaccharide (LOS) bilayer systems and oligosaccharides (OS) in water solution to investigate the conformational similarities and differences of three serotypes. For up to 10 neutral monosaccharides in the core part, the conformational ensembles described by the pair-wise root mean square deviation distributions are similar among the three serotypes of either the LOS or OS. At the central β-($1\to4$)-linkage, anti-$\psi$ conformation in conjunction with the gauche-gauche (g-) conformation of the central trisubstituted glucosyl residue is observed as the dominant conformation to sustain the structural characteristics of M. catarrhalis three types, which is further supported by calculated transglycosidic ${}^3{J}_{C,H}\Big({\psi}_H\Big)$ of serotype A in comparison to experimental data. Interestingly, the conformational variability of three serotypes is more restricted for the OS in water solution than that in the LOS bilayer systems. The LOS-LOS interactions in the bilayer systems are responsible for the increased conformational diversity despite of tight packing. Solvent-accessible surface area analysis suggests that a trisaccharide attached to the β-($1\to 6$)-linked sugar in all three serotypes of LOS could be the common epitope and have the possibility to interact with antibodies.

中文翻译：

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卡他莫拉氏菌的脂寡糖和寡糖的优选构象。

卡他莫拉菌（M. catarrhalis）是一种致病性革兰氏阴性细菌，可引起儿童中耳炎和鼻窦炎。确定了三种主要血清型A，B和C，约占临床分离株的95％。了解不同血清类型的卡他莫拉菌的构象性质，可以深入了解抗原决定簇。在这项工作中，对粘膜炎莫拉氏菌低脂寡糖（LOS）双层系统和水溶液中的低聚糖（OS）进行了全原子分子动力学模拟，以研究三种血清型的构象异同。对于核心部分中多达10个中性单糖，在LOS或OS的三种血清型中，由成对的均方根偏差分布描述的构象集合相似。在中央β-（$ 1 \ to4 $）链上，观察到反$ \ psi $构象与中央三取代的葡糖基残基的gauche-gauche（g-）构象一起是维持结构特征的主要构象粘膜炎莫拉氏菌的三种类型，与实验数据相比，计算得出的血清型A的转糖苷$ {} ^ 3 {J} _ {C，H} \ Big（{\ psi} _H \ Big）$支持。有趣的是，与LOS双层系统相比，水溶液中OS的三种血清型的构象变异性受到更大的限制。尽管包装紧密，双层系统中的LOS-LOS相互作用还是导致构象多样性增加的原因。