Global Application Development Center, Analytical & Measuring Instruments Division, Shimadzu Corporation, 1, Nishinokyo-Kuwabaracho, Nakagyo-ku, Kyoto 604-8511, Japan.
Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan.
J Am Soc Mass Spectrom. 2020 Jun 3;31(6):1180-1188. doi: 10.1021/jasms.9b00084. Epub 2020 May 1.
Polyrotaxane (PR) is a necklace-like supramolecule composed of cyclic components, such as cyclodextrin (CD), and a threading polymer capped with bulky end groups. PR exhibits peculiar mechanical properties attributed to the intermolecular cross-links with CD. Various CD molecules threaded on a linear PEG chain are often modified with chemical groups to add specific physicochemical properties. In general, the stoichiometry between CD and the PEG chain is a significant parameter that defines the unique physical properties of CD-based polyrotaxane (CD-PR). To date, mass spectrometry (MS) has been applied to investigate the molecular distribution of CD-PR, modifications of CD, and the threaded ratio of CD. However, only molecular weights (MWs) up to several 10s of kDa can be subjected to such analysis, whereas the MW of CD-PR used as industrial materials is much greater. Herein, we applied two ionic liquid matrices composed of 3-aminoquinoline and a high mass detector to analyze PRs using MALDI-TOF-MS. High to very high MW PRs in the range of 90-700 kDa were successfully analyzed using this method. The threaded ratio of CD was estimated from a single MW of CD, PEG, and PR. The ratios obtained were consistent with that obtained using H NMR. Furthermore, a single-stranded form of PR in γ-cyclodextrin threaded PR (γCD-PR) was clearly distinguished from a double-stranded form, which is only possible in γCD -PR because of its large host cavity.
聚轮烷（PR）是一种项链状的超分子，由环状分子（如环糊精（CD））和带有大端基的穿线聚合物组成。PR 表现出特殊的机械性能，归因于与 CD 的分子间交联。各种 CD 分子穿在线性 PEG 链上通常用化学基团修饰以添加特定的物理化学性质。通常，CD 和 PEG 链之间的化学计量比是定义基于 CD 的聚轮烷（CD-PR）独特物理性质的重要参数。迄今为止，质谱（MS）已被用于研究 CD-PR 的分子分布、CD 的修饰以及 CD 的穿线比。然而，只能对分子量（MW）高达几十万的 CD-PR 进行这种分析，而用作工业材料的 CD-PR 的 MW 要大得多。在此，我们应用由 3-氨基喹啉组成的两种离子液体基质和高质量检测器，使用 MALDI-TOF-MS 分析 PR。使用该方法成功分析了 MW 为 90-700 kDa 的高至非常高 MW 的 PR。从 CD、PEG 和 PR 的单个 MW 估计 CD 的穿线比。得到的比值与使用 H NMR 得到的比值一致。此外，γ-环糊精穿线 PR（γCD-PR）中的 PR 单链形式与双链形式明显区分开，这在 γCD-PR 中是唯一可能的，因为其大的主体腔。
