Silk fibroin/montmorillonite nanocomposites: effect of pH on the conformational transition and clay dispersion.
By adjusting the solution pH value below the isoelectric point (pI) of silk fibroin (SF) protein, the SF was in the cation state and it could interact strongly with unmodified anionic montmorillonite (MMT) surface. In this way, novel SF-MMT nanocomposites with good clay dispersion were successfully obtained, which were confirmed by X-ray diffraction and transmission electron microscopy. Further 1H CRAMPS and 13C CP/MAS NMR experimental results revealed that beta-sheet content of SF was remarkably enhanced for nanocomposite prepared below the pI of SF (SF-MMTA) due to the strong interaction between MMT and SF. In SF-MMTA nanocomposite, clay layers acting as an efficient nucleator could efficiently enhance the beta-sheet crystallization. On the contrary, SF preserved the native random coil conformation in SF-MMTN nanocomposites due to the weak interaction between MMT and SF. A tentative model was suggested and used to explain the mechanism of clay dispersion and conformational transition of silk protein.
Dang
Qinqin
Q
Key Laboratory of Functional Polymer Materials, Ministry of Education, Institute of Polymer Chemistry and College of Chemistry, Nankai University, Tianjin, 300071, People's Republic of China.
Lu
Shoudong
S
Yu
Shen
S
Sun
Pingchuan
P
Yuan
Zhi
Z
D000538:Aluminum Silicates; D001546:Bentonite / Q000737:chemistry*; D000077215:Clay; D005349:Fibroins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D046529:Microscopy, Electron, Transmission; D053761:Nanocomposites / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D014961:X-Ray Diffraction
D000538:Aluminum Silicates; D001546:Bentonite; D005349:Fibroins; D000077215:Clay