This work revisits several open questions regarding the mechanisms of GAG fibril formation and structure as a function of temperature. The authors recently hypothesized that there is a solubility limit of GAG in ethanol/water that induces self‐assembly. In other words, not all peptides can participate in fibrillization and some fraction is still soluble in solution. We show via FTIR spectroscopy that, indeed, free peptides are still present in solution after fibril formation, strongly supporting the solubility model. Furthermore, previous work showed GAG self‐assembled into right‐handed (phase I) or left‐handed (phase II) chiral structures depending on temperature. In this study, we analyze the crystalline structure of phase I and II gels via WAXS and SAXS to compare their crystalline structures and order. Rheological measurements were used to investigate the response of the fibrillar network to temperature. They reveal that the ability of the peptide to self‐assemble depends on the solubility at a given temperature and not on thermal history. Furthermore, the gel softening point, the linear viscoelastic gel microstructure, and relaxation spectrum are very similar between phase I and phase II. Overall, the temperature only affects the chirality of the fibrils and the formation kinetics.

中文翻译：

---

热历史对甘氨酰丙氨酰甘氨酸乙醇/水凝胶结构的影响

这项工作重新审视了关于作为温度函数的 GAG 原纤维形成和结构的机制的几个悬而未决的问题。作者最近假设 GAG 在乙醇/水中的溶解度限制会诱导自组装。换句话说，并非所有的肽都能参与原纤维化，一些部分仍可溶于溶液。我们通过 FTIR 光谱表明，事实上，在原纤维形成后，游离肽仍然存在于溶液中，有力地支持了溶解度模型。此外，先前的工作表明，GAG 根据温度自组装成右手（I 相）或左手（II 相）手性结构。在本研究中，我们通过 WAXS 和 SAXS 分析 I 相和 II 相凝胶的晶体结构，以比较它们的晶体结构和顺序。流变测量用于研究原纤维网络对温度的响应。他们揭示了肽的自组装能力取决于给定温度下的溶解度，而不是热历史。此外，I 相和 II 相之间的凝胶软化点、线性粘弹性凝胶微观结构和松弛谱非常相似。总的来说，温度只影响原纤维的手性和形成动力学。