Reversible stiffening transition in beta-hairpin hydrogels induced by ion complexation.
Reversible stiffening transition in beta-hairpin hydrogels induced by ion complexation.
复制标题
DOI：
10.1021/jp075117p
复制
发表时间：
2007-12
期刊：
影响因子：
--
通讯作者：
B. Ozbas;K. Rajagopal;Lisa A Haines-Butterick;J. Schneider;D. Pochan
中科院分区：
文献类型：
--
作者：
B. Ozbas;K. Rajagopal;Lisa A Haines-Butterick;J. Schneider;D. Pochan
我们之前已经证明，正确设计的富含赖氨酸和缬氨酸的肽会经历随机卷曲到β-发夹的转变，然后仅在肽溶液被加热到分子内折叠转变温度以上后，分子间自组装成纤维状水凝胶网络。在这里，我们报告说，只有当使用硼酸缓冲肽溶液时，这些水凝胶才会冷却到临界温度以下，从而经历硬化转变。这种硬化转变的特征在于流变学、动态光散射和小角度中子散射。流变学测量表明，硬化转变导致水凝胶储能模量 (G') 增加多达 1 个数量级，并且在随后升高温度时完全可逆。尽管这种可逆转变表现出与多元醇/硼砂溶液相似的流变特性，但其基本机制不涉及羟基硼酸盐络合。硬化转变主要是由赖氨酸和硼酸/硼酸盐阴离子之间的相互作用引起的，而不是由β-发夹肽二级结构的变化驱动的。由于竞争性葡萄糖-硼酸盐络合，向硼酸和肽溶液中添加葡萄糖会破坏硬化转变。
We have previously shown that properly designed lysine and valine-rich peptides undergo a random coil to beta-hairpin transition followed by intermolecular self-assembly into a fibrillar hydrogel network only after the peptide solutions are heated above the intramolecular folding transition temperature. Here we report that these hydrogels also undergo a stiffening transition as they are cooled below a critical temperature only when boric acid is used to buffer the peptide solution. This stiffening transition is characterized by rheology, dynamic light scattering, and small angle neutron scattering. Rheological measurements show that the stiffening transition causes an increase in the hydrogel storage modulus (G') by as much as 1 order of magnitude and is completely reversible on subsequently raising the temperature. Although this reversible transition exhibits rheological properties that are similar to polyol/borax solutions, the underlying mechanism does not involve hydroxyl-borate complexation. The stiffening transition is mainly caused by the interactions between lysine and boric acid/borate anion and is not driven by the changes in the secondary structure of the beta-hairpin peptide. Addition of glucose to boric acid and peptide solution disrupts the stiffening transition due to competitive glucose-borate complexation.