Responsive pure protein organogel sensors and catalysts are fabricated by replacing the aqueous mobile phase of protein hydrogels with pure ethylene glycol (EG). Exchanging water for EG causes irreversible volume phase transitions (VPT) in bovine serum albumin (BSA) polymers; however, BSA hydrogel and organogel sensors show similar volume responses to protein-ligand binding. This work elucidates the mechanisms involved in this enabling irreversible VPT by examining the protein secondary structure, hydration, and protein polymer morphology. Organogel proteins retain their native activity because their secondary structure and hydration shell are relatively unperturbed by the EG exchange. Conversely, the decreasing solvent quality initiates polymer phase separation to minimize the BSA polymer surface area exposed to EG, thus decreasing distances between BSA polymer strands. These protein polymer morphology changes promote interprotein interactions between BSA polymer strands, which increase the effective polymer cross-link density and prevent organogel swelling as the mobile phase is exchanged back to water.

中文翻译：

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有机溶剂交换将响应性纯蛋白水凝胶转变为响应性有机胶的机理。

通过用纯乙二醇（EG）代替蛋白质水凝胶的水相，可以制造出响应性的纯蛋白质有机凝胶传感器和催化剂。用水交换EG会在牛血清白蛋白（BSA）聚合物中引起不可逆的体积相变（VPT）；但是，BSA水凝胶和有机凝胶传感器对蛋白质-配体的结合表现出相似的体积响应。这项工作通过检查蛋白质的二级结构，水合和蛋白质聚合物的形态，阐明了实现不可逆VPT的机制。有机凝胶蛋白保留其天然活性，因为它们的二级结构和水合壳不受EG交换的干扰。相反，降低的溶剂质量会引发聚合物相分离，以最大程度减少暴露于EG的BSA聚合物表面积，因此减少了BSA聚合物链之间的距离。这些蛋白质聚合物的形态变化促进了BSA聚合物链之间的蛋白质间相互作用，从而增加了有效的聚合物交联密度，并防止了当流动相交换回水中时有机凝胶膨胀。