Disruption of the Metal Ion Environment by EDTA for Silk Formation Affects the Mechanical Properties of Silkworm Silk
Abstract
:1. Introduction
2. Results and Discussion
2.1. Observation of Morphological Characteristics
2.2. EDTA Disturbed the Ionic Environment for Silk Fiber Formation
2.3. Secondary Structure Analysis
2.4. Mechanical Performance of Silk Fiber
2.5. Current Advances in the Effect of Metal Ions on the Structure and Performance of Silk In Vitro and In Vivo
3. Materials and Methods
3.1. Silkworms
3.2. Experimental Design
3.2.1. Injecting EDTA to Silkworms (IEDTA)
3.2.2. Feeding EDTA to Silkworms (FEDTA)
3.3. Elemental Analysis
3.4. FTIR Spectroscopy of a Single Silk Fiber
3.5. Mechanical Testing of Silk Fiber
3.6. Statistical Analysis
4. Conclusions
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
Abbreviations
EDTA | Ethylenediaminetetraacetic acid |
EDTA·2Na·2H2O | Ethylenediaminetetraacetic acid disodium salt |
FTIR | Fourier Transform Infrared Spectroscopy |
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Secondary Structures (%) | Injecting EDTA | Feeding EDTA | ||||
---|---|---|---|---|---|---|
0 mM | 10 mM | 50 mM | 0 mM | 100 mM | 500 mM | |
β-sheet | 32.29 ± 1.41 | 26.85 ± 1.60 | 28.27 ± 1.7 | 28.22 ± 3.0 | 26.4 ± 1.5 | 26.37 ± 2.8 |
Random coil and Helix | 53.1 ± 2.58 | 53.25 ± 1.0 | 53.25 ± 1.2 | 56.8 ± 5.0 | 53 ± 0.6 | 54 ± 1.1 |
β-turn | 13.56 ± 0.80 | 20.06 ± 2.2 | 18.6 ± 1.0 | 14.93 ± 3.0 | 20.4 ± 1.0 | 19.4 ± 2.0 |
Metal Ions | In Vitro | In Vivo |
---|---|---|
Secondary Structure | Mechanical Performance | |
Ca2+ | α-helical intermediate conformation [37] | Injection of CaCl2: strain increased 30.9% [18] |
Forming a stable protein network [15,18] | Transgenic silkworm: strength/strain increased 21.1%/73.1% [19] | |
Na+ | Break down the protein network [15] | Transgenic silkworm: the average tenacity, Young’s modulus, and toughness of the transgenic silks decreased significantly [19] |
K+ | Decrease β-sheet like conformation and break down the protein network [15,38] | Injection of KCl: strength increased 71.4% [17] |
Cu2+ | β-sheet increased [13,15,17] | Injection of CuCl2: strength increased 51.9% [17] |
Fe2+ | Less influence [36] | Not reported |
Fe3+ | β-sheet increased [16,36,39] | Injection of FeCl3: strength/toughness increased 13%/29% [16] |
Mg2+ | β-sheet increased [15] | Not reported |
Zn2+ | β-sheet increased [15,40] | Not reported |
Mn2+ | Stabilizing the Silk I state [41] | Not reported |
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Liu, Q.; Wang, X.; Tan, X.; Xie, X.; Dong, H.; Li, X.; Li, Y.; Zhao, P.; Xia, Q. Disruption of the Metal Ion Environment by EDTA for Silk Formation Affects the Mechanical Properties of Silkworm Silk. Int. J. Mol. Sci. 2019, 20, 3026. https://doi.org/10.3390/ijms20123026
Liu Q, Wang X, Tan X, Xie X, Dong H, Li X, Li Y, Zhao P, Xia Q. Disruption of the Metal Ion Environment by EDTA for Silk Formation Affects the Mechanical Properties of Silkworm Silk. International Journal of Molecular Sciences. 2019; 20(12):3026. https://doi.org/10.3390/ijms20123026
Chicago/Turabian StyleLiu, Qingsong, Xin Wang, Xiaoyin Tan, Xiaoqian Xie, Haonan Dong, Xinning Li, Yi Li, Ping Zhao, and Qingyou Xia. 2019. "Disruption of the Metal Ion Environment by EDTA for Silk Formation Affects the Mechanical Properties of Silkworm Silk" International Journal of Molecular Sciences 20, no. 12: 3026. https://doi.org/10.3390/ijms20123026