丝素蛋白自组装和结晶中的酪氨酸模板化,Biomacromolecules

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丝素蛋白自组装和结晶中的酪氨酸模板化
Biomacromolecules ( IF 5.5 ) Pub Date : 2016-10-21 00:00:00 , DOI: 10.1021/acs.biomac.6b01086
Benjamin P. Partlow ₁ , Mehran Bagheri ₂ , James L. Harden ₂ , David L. Kaplan ₁

Affiliation

天然丝纤维的强度和韧性可与最佳合成纤维相媲美。尽管进行了大量研究，但仍需要进一步的研究来了解蚕能够纺出这种坚韧纤维的机制。在这里，我们提出酪氨酸侧链的π-π和π-OH基团相互作用提供了模板效应，从而使晶体形成域处于配准状态，从而促进了纺丝原液的自组装。内在荧光测量与圆二色性一起显示，在再生丝溶液的自组装过程中，酪氨酸残基位于疏水性更高的局部环境中，表明优先组装。原位傅里叶变换红外光谱表明，酪氨酸残基的交联导致扩展的β-折叠结构的发展。另外，交联密度的控制直接影响干燥时的结晶度。为了更全面地了解酪氨酸的作用，对真丝模拟肽进行了分子动力学模拟。结果表明，由于π-π相互作用以及与相邻残基和肽主链的氢键作用，酪氨酸残基倾向于在溶液中瞬时共位。这些更稳定的酪氨酸相互作用导致减少的侧链波动和增加的链内配位缔合的发生率，而引入二酪氨酸键则直接促进了β-折叠结构的形成。总共，

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Tyrosine Templating in the Self-Assembly and Crystallization of Silk Fibroin

Native silk fibers exhibit strength and toughness that rival those of the best synthetic fibers. Despite significant research, further insight is still needed to understand the mechanisms by which silkworms are capable of spinning such tough fibers. Here we propose that π–π and π–OH group interactions of tyrosine side chains provide templating effects, such that the crystal-forming domains are in registration, thereby fostering the self-assembly of the spinning dope. Intrinsic fluorescence measurements, in conjunction with circular dichroism, showed that during self-assembly of regenerated silk solutions, the tyrosine residues were localized in a more hydrophobic local environment, suggesting preferential assembly. In situ Fourier transform infrared spectroscopy indicated that cross-linking of the tyrosine residues resulted in the development of extended β-sheet structure. Additionally, control of cross-link density directly influenced the degree of crystallinity upon drying. Molecular dynamics simulations were performed on silk mimetic peptides in order to more thoroughly understand the role of tyrosines. The results indicated that tyrosine residues tended to transiently colocate in solution due to π–π interactions and hydrogen bonds with adjacent residues and with the peptide backbone. These more stable tyrosine interactions resulted in reduced lateral chain fluctuations and increased incidence of coordinated intrachain association, while introduction of a dityrosine bond directly promoted the formation of β-sheet structures. In total, the experimental and modeling data support a critical role for tyrosine-tyrosine interactions as a key early feature in the self-assembly of regenerated silk protein chains and therefore are important in the robust and unusual mechanical properties ultimately achieved in the process.

更新日期：2016-10-21

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