Activation of Upper Critical Solution Temperature Behaviors of Zwitterionic Poly(l-methionine-g-poly(sulfobetaine methacrylate)m) with a Bottlebrush Structure,Macromolecules

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Activation of Upper Critical Solution Temperature Behaviors of Zwitterionic Poly(l-methionine-g-poly(sulfobetaine methacrylate)m) with a Bottlebrush Structure
Macromolecules ( IF 5.1 ) Pub Date : 2023-12-19 , DOI: 10.1021/acs.macromol.3c01920
Yueqi Deng ₁ , Binlin Chen ₁ , Kongying Zhu ₂ , Lixia Ren ₁ , Xiaoyan Yuan ₁

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Aqueous poly(sulfobetaine methacrylate) (PSBMA) solutions exhibit upper critical solution temperature (UCST) behaviors, which are influenced by the topological structure and relative molar mass of the polymer chain. In this study, a series of well-defined PSBMA-based zwitterionic bottlebrush poly(l-methionine) derivatives, namely, poly(l-methionine-g-(PSBMA)_m) (MS-m), were synthesized via ring-opening polymerization of l-methionine N-carboxyanhydride, followed by bromo-alkylation and atom transfer radical polymerization. The aqueous MS-70 (m = 70) solution showed UCST-type thermoresponsive properties with a cloud point (T_cp) at around 38.6 °C. The variable temperature nuclear magnetic resonance results of ¹H and 2D ¹H–¹H correlated spectroscopy and nuclear Overhauser effect spectroscopy (NOESY) demonstrated correlated peaks and coupling interactions between protons in the sulfobetaine units. When the temperature increased up to or beyond T_cp, the NOESY spectra showed that the zwitterionic bottlebrush MS-70 polypeptides transformed from the aggregated state to the monodisperse state owing to the weakened inter/intramolecular interactions between the positively and negatively charged groups. In contrast, the observed UCST transition near the physiological temperatures could be negligible in linear PSBMA or the linear-like SBMA polymer of MS-70 degraded by papain. Results indicated that the bottlebrush structure activated the solution properties of zwitterions. In brief, this study presents a precise strategy for synthesizing zwitterionic bottlebrush polypeptides with an elucidated mechanism of thermal responsiveness in aqueous solution. It provides valuable insights into expanding applications of zwitterions in biology, such as protein stabilization or zwitterionic hydrogels.

中文翻译：

具有洗瓶刷结构的两性离子聚(l-蛋氨酸-g-聚(磺基甜菜碱甲基丙烯酸酯)m)的上临界溶液温度行为的激活

聚（磺基甜菜碱甲基丙烯酸酯）（PSBMA）水溶液表现出上临界溶液温度（UCST）行为，该行为受到聚合物链的拓扑结构和相对摩尔质量的影响。在本研究中，通过开环合成了一系列明确的基于PSBMA的两性离子瓶刷聚( l-蛋氨酸)衍生物，即聚( l-蛋氨酸-g- (PSBMA) _m )(MS- m ) L-蛋氨酸N-羧酸酐聚合，然后进行溴烷基化和原子转移自由基聚合。MS-70 ( m = 70) 水溶液表现出 UCST 型热响应特性，浊点 ( T _cp ) 约为 38.6 °C。¹ H 和 2D ¹ H- ¹ H 相关光谱和核欧沃豪瑟效应光谱 (NOESY)的变温核磁共振结果证明了磺基甜菜碱单元中质子之间的相关峰和耦合相互作用。当温度升高至或超过T _cp时，NOESY 谱显示，由于正电荷基团和负电荷基团之间的分子间/内相互作用减弱，两性离子瓶刷MS-70 多肽从聚集状态转变为单分散状态。相比之下，在线性 PSBMA 或被木瓜蛋白酶降解的 MS-70 的线性 SBMA 聚合物中，观察到的接近生理温度的 UCST 转变可以忽略不计。结果表明，瓶刷结构激活了两性离子的溶液特性。简而言之，本研究提出了一种精确的合成两性离子洗瓶刷多肽的策略，并阐明了水溶液中的热响应性机制。它为扩大两性离子在生物学中的应用（例如蛋白质稳定或两性离子水凝胶）提供了宝贵的见解。

更新日期：2023-12-19

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