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Energy Landscape of the Sugar Conformation Controls the Sol-to-Gel Transition in Self-Assembled Bola Glycolipid Hydrogels
Chemistry of Materials ( IF 7.2 ) Pub Date : 2022-06-13 , DOI: 10.1021/acs.chemmater.2c00580 Alexandre Poirier 1 , Patrick Le Griel 1 , Thomas Zinn 2 , Petra Pernot 2 , Sophie L. K. W. Roelants 3, 4 , Wim Soetaert 3, 4 , Niki Baccile 1
Chemistry of Materials ( IF 7.2 ) Pub Date : 2022-06-13 , DOI: 10.1021/acs.chemmater.2c00580 Alexandre Poirier 1 , Patrick Le Griel 1 , Thomas Zinn 2 , Petra Pernot 2 , Sophie L. K. W. Roelants 3, 4 , Wim Soetaert 3, 4 , Niki Baccile 1
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Self-assembled fibrillar network hydrogels and organogels are commonly obtained through a crystallization process as fibers upon being induced by external stimuli such as temperature or pH. The gel-to-sol-to-gel transition is generally readily reversible, and the rate of change of the stimulus determines the fiber homogeneity and eventual elastic properties of the gels. However, recent work shows that in some specific cases, fibrillation occurs for a given molecular conformation and the sol-to-gel transition depends on the relative energetic stability of one conformation over the other and not on the rate of change of the stimuli. We observe such a phenomenon on a class of bolaform glycolipids, sophorosides, similar to the well-known sophorolipid biosurfactants but composed of two symmetric sophorose units. A combination of oscillatory rheology, small-angle X-ray scattering (SAXS), cryogenic transmission electron microscopy, and in situ rheology coupled with SAXS using synchrotron radiation shows that below 14 °C, twisted nanofibers are the thermodynamic phase. Between 14 and about 33 °C, nanofibers coexist with micelles and a strong hydrogel forms, the sol-to-gel transition being readily reversible in this temperature range. However, above the annealing temperature of about 40 °C, the micelle morphology becomes kinetically trapped for hours, even upon cooling, whichever the rate, to 4 °C. A combination of solution and solid-state nuclear magnetic resonance spectroscopy studies suggests two different conformations of the 1″, 1′, and 2′ carbon stereocenters of sophorose, precisely at the β(1,2) glycosidic bond, for which several combinations of the dihedral angles are known to provide at least three energetic minima of comparable magnitude, with each corresponding to a given sophorose conformation.
中文翻译：
糖构象的能量景观控制自组装 Bola 糖脂水凝胶中的溶胶到凝胶的转变
自组装纤维状网络水凝胶和有机凝胶通常通过结晶过程作为纤维在受到外部刺激（如温度或 pH 值）诱导时获得。凝胶到溶胶到凝胶的转变通常很容易可逆，并且刺激的变化率决定了凝胶的纤维均匀性和最终的弹性特性。然而，最近的工作表明，在某些特定情况下，给定分子构象会发生原纤维化，并且溶胶到凝胶的转变取决于一种构象相对于另一种构象的相对能量稳定性，而不是刺激的变化率。我们在一类 bolaform 糖脂槐糖苷上观察到这种现象，类似于众所周知的槐糖脂生物表面活性剂，但由两个对称的槐糖单元组成。振荡流变学的结合，小角 X 射线散射 (SAXS)、低温透射电子显微镜和使用同步辐射与 SAXS 耦合的原位流变学表明，在 14 °C 以下，扭曲的纳米纤维是热力学相。在 14 至约 33 °C 之间，纳米纤维与胶束共存并形成强水凝胶，在此温度范围内溶胶到凝胶的转变很容易逆转。然而，在约 40 °C 的退火温度以上，胶束形态在数小时内被动力学捕获，即使在冷却至 4 °C 时（无论以何种速率）。溶液和固态核磁共振波谱研究的结合表明槐糖的 1"、1' 和 2' 碳立体中心有两种不同的构象，恰好在 β(1,2) 糖苷键处，
更新日期：2022-06-13
中文翻译：
糖构象的能量景观控制自组装 Bola 糖脂水凝胶中的溶胶到凝胶的转变
自组装纤维状网络水凝胶和有机凝胶通常通过结晶过程作为纤维在受到外部刺激（如温度或 pH 值）诱导时获得。凝胶到溶胶到凝胶的转变通常很容易可逆，并且刺激的变化率决定了凝胶的纤维均匀性和最终的弹性特性。然而，最近的工作表明，在某些特定情况下，给定分子构象会发生原纤维化，并且溶胶到凝胶的转变取决于一种构象相对于另一种构象的相对能量稳定性，而不是刺激的变化率。我们在一类 bolaform 糖脂槐糖苷上观察到这种现象，类似于众所周知的槐糖脂生物表面活性剂，但由两个对称的槐糖单元组成。振荡流变学的结合，小角 X 射线散射 (SAXS)、低温透射电子显微镜和使用同步辐射与 SAXS 耦合的原位流变学表明，在 14 °C 以下，扭曲的纳米纤维是热力学相。在 14 至约 33 °C 之间，纳米纤维与胶束共存并形成强水凝胶，在此温度范围内溶胶到凝胶的转变很容易逆转。然而，在约 40 °C 的退火温度以上，胶束形态在数小时内被动力学捕获，即使在冷却至 4 °C 时（无论以何种速率）。溶液和固态核磁共振波谱研究的结合表明槐糖的 1"、1' 和 2' 碳立体中心有两种不同的构象，恰好在 β(1,2) 糖苷键处，
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