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| Influence of Ca2+ on Silk Fibroin Structure in the Process of Dissolution by Optical Spectroscopy |
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| DOI：10.3969/j.issn.1004-4957.年份.月份 |
| KeyWord:silk fibroin conformation transition fluorescence spectrum ultraviolet-visible absorption Raman spectroscopy |
| Author | Institution |
| DONG Wen-xiu，LI Jun-sheng*，LI Qiu-jie，YAN Liu-juan，HUANG Guo-xia |
广西科技大学生物与化学工程学院 |
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| Abstract: |
| In order to study the structural periodic variation characteristics of silk fibroin dissolved in calcium chloride，spectroscopic techniques（e.g.static fluorescence spectroscopy，UV-vis absorption spectroscopy and Raman spectroscopy） were used to monitor and investigate the conformational transition of silk fibroin in aqueous solutions under different dissolution time for the first time.It was shown that silk fibroin dissolved in calcium chloride（CaCl2∶H2O=111∶180，mass ratio） at about 90 ℃.With the extension of dissolution time from 0 min to 30 min，calcium ions progressively penetrated into the silk fibroin molecules，and forming chelate complex with hydroxyl ligand of serine（Ser） and tyrosine（Tyr） side chain.In addition，silk fibroin began to swell，molecular structure also became gradually loose.At the same time，tryptophan（Trp） and Tyr buried in the area of noncrystalline also were gradually exposed，molecular conformation was also mainly shifted from β-sheet crystal to α-helix or random coil.It was also found that the aggregating of hydrophobic side chains was increased with increase of dissolution time via exogenous fluorescence probe of 8-anilino-1-naphthalenesulfonic acid（ANS）.Experimental results obtained from the scanning electron microscope（SEM） confirmed that almost all of silk fibers were dissolved within 30 min，presenting globular structure.While previously，a certain amount of residual fibroin fibers existed with relatively loose zonal structure，then becoming layered structure.Therefore，the results obtained have a important practical significance for the time controlling of silk fibroin dissolution in calcium chloride solution. |
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