Mechanisms of silk fibroin sol-gel transitions
Mechanisms of silk fibroin sol-gel transitions
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DOI：
10.1021/jp056350v
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发表时间：
2006-11-02
影响因子：
3.3
通讯作者：
Kaplan, David L.
中科院分区：
文献类型：
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作者：
Matsumoto, Akira;Chen, Jingsong;Kaplan, David L.
通过使用 550 nm 光谱监测各种物理化学条件下的过程来研究丝素蛋白溶胶-凝胶转变。通过 FTIR 和 CD 在一定范围的丝心蛋白浓度、温度和 pH 值范围内评估丝心蛋白从溶液中的无序状态到凝胶状态下富含 β-折叠的构象的二级结构变化。基于 550 nm 光密度的变化，结构变化与凝胶化程度相关。在约 15% 凝胶化（550 nm）时，未发现蛋白质二级结构（FTIR、CD）发生可检测的变化，这表明这些凝胶化的早期阶段并不伴随着 β-折叠的形成。超过15%时，β-折叠的比例随凝胶化程度线性增加。发现胶凝时间的 pH 依赖性与丝中主要的酸性侧链相关。静电相互作用与中性 pH 值以上的凝胶化速率相关。加工参数（包括浓度、温度和 pH 值）对凝胶形成和蛋白质结构的总体独立性可能与丝心蛋白分子组织中的初级序列特异性特征相关。这些发现阐明了这一独特蛋白质家族的自组装的各个方面，作为控制材料特性的途径，以及对具有可预测的溶液和组装特性的合成丝仿生聚合物的设计提供新的见解。
Silk fibroin sol-gel transitions were studied by monitoring the process under various physicochemical conditions with optical spectroscopy at 550 nm. The secondary structural change of the fibroin from a disordered state in solution to a beta-sheet-rich conformation in the gel state was assessed by FTIR and CD over a range of fibroin concentrations, temperatures, and pH values. The structural changes were correlated to the degree of gelation based on changes in optical density at 550 nm. No detectable changes in the protein secondary structure (FTIR, CD) were found up to about 15% gelation (at 550 nm), indicating that these early stages of gelation are not accompanied by the formation of beta-sheets. Above 15%, the fraction of beta-sheet linearly increased with the degree of gelation. A pH dependency of gelation time was found with correlation to the predominant acidic side chains in the silk. Electrostatic interactions were related to the rate of gelation above neutral pH. The overall independencies of processing parameters including concentration, temperature, and pH on gel formation and protein structure can be related to primary sequence-specific features in the molecular organization of the fibroin protein. These findings clarify aspects of the self-assembly of this unique family of proteins as a route to gain control of material properties, as well as for new insight into the design of synthetic silk-biomimetic polymers with predictable solution and assembly properties.