An investigation into the effect of potassium ions on the folding of silk fibroin studied by generalized two-dimensional NMR-NMR correlation and Raman spectroscopy
An investigation into the effect of potassium ions on the folding of silk fibroin studied by generalized two-dimensional NMR-NMR correlation and Raman spectroscopy
复制标题
用广义二维NMR-NMR关联和拉曼光谱研究钾离子对丝素蛋白折叠的影响
DOI：
10.1111/j.1742-4658.2007.06191.x
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发表时间：
2008-01-01
期刊：
影响因子：
5.4
通讯作者：
Ji, Dan
中科院分区：
文献类型：
--
作者：
Ruan, Qing-Xia;Zhou, Ping;Ji, Dan
我们使用广义二维 NMR-NMR 相关性来检查钾离子对丝素蛋白构象转变的影响，以研究蚕丝分泌管远端中发现的相当高的 K+ 离子含量可能对丝纤维的自然形成产生影响的可能性。这使我们能够为过渡过程提出详细的机制。我们的证据表明，将丝素蛋白中的 [K+] 从 0 增加到 3.7 mg.g(-1)，正如人们认为当丝素蛋白通过分泌途径移动到套管时发生的那样，会产生一系列二级结构变化：螺旋和/或无规卷曲 -> 螺旋状 -> β 片状 -> β 片层。该序列与通过将丝素蛋白的pH值从6.8降低至4.8而在丝素蛋白膜中产生的序列相同。此外，我们利用拉曼光谱研究了K+离子对酪氨酚环850和830 cm(-1)处费米双峰共振的影响。这些波数下的强度比I-850/I-830表明，如上所述，随着K+离子浓度的增加，由酪氨酰酚-OH形成的氢键变得更加稳定。我们对 K+ 离子对丝心蛋白影响的研究可能有助于为理解天然丝纺过程和仿生纺丝所需的条件提供理论基础。它还可能与其他 β-折叠蛋白的聚集有关，包括朊病毒蛋白、神经原纤维蛋白和淀粉样斑块。
We used generalized two-dimensional NMR-NMR correlation to examine the effect of potassium ions on the conformation transition in silk fibroin to investigate the possibility that the fairly high K+ ion content found in the distal end of silk-secreting ducts in the silkworms could have a bearing on natural formation of the silk fiber. This has enabled us to propose a detailed mechanism for the transition process. Our evidence indicates that increasing the [K+] from 0 to 3.7 mg.g(-1) in the silk fibroin, as is thought to occur as the silk fibroin moves through the secretory pathway to the spigot, produces a sequence of secondary structural changes: helix and/or random coil -> helix-like ->beta-sheet-like ->beta-sheet. The sequence is the same as that produced in silk fibroin films by decreasing the pH of fibroin from 6.8 to 4.8. In addition, we used Raman spectroscopy to study the effect of K+ ions on the Fermi doublet resonance of the tyrosyl phenolic ring at 850 and 830 cm(-1). The intensity ratio I-850/I-830 at these wave numbers indicated that the hydrogen bonding formed by the tyrosyl phenolic-OH becomes more stable with an increase in the K+ ion concentration as above. Our investigation on the effect of K+ ions on fibroin may help provide a theoretical basis for understanding the natural silk-spinning process and the conditions required for biomimetic spinning. It may also have relevance to the aggregation of other beta-sheet proteins, including prion proteins, neurofibrillary proteins and amyloid plaques.