Interaction Of Curcumin With Metal Ions And Silk Fibroin

Our research took the two metal ions, Zn(Ⅱ) and Cu(Ⅱ) as example, synthesized and characterized their complexes with curcumin. We also investigate the silk fibroin-metal ions-curcumin system. We made a deep insight into the structure and properties of the complexes, and the interaction among curcumin, metal ions and silk fibroin, in order to understand the mechanism of curcumin interacting with different metal ions and silk fibroin. and try to explain the effect of curcumin in the treatment of Alzheimer's disease.1. We characterized curcumin using elemental analysis, IR, UV. MS,1H NMR, 13C NMR and DFT calculation. The most stable structure of curcumin is keto-enol form with Trans structure. Curcumin has a strong conjugating system throughout it whole molecule.2. We synthesized the complex between Zn(Ⅱ) and curcumin and characterized it using elemental analysis, IR. UV. ESI MS.1H NMR, solid-state 13C CP/MAS NMR and DFT calculation. and compared it with curcumin. The results indicated that the interacting position of curcumin with Zn(Ⅱ) is its keto-enol H. The interacting ratio of curcumin to Zn(Ⅱ) is 1:1, with the other two ligands-OH and H2O. Zn(Ⅱ) formed tetrahedron-like complex with the four O atoms around. The conjugating system and free-radical scavenging ability of the complex decreased compared with curcumin.3. We synthesized the complex between Cu(Ⅱ) and curcumin and characterized it using elemental analysis, IR, UV, MALDI-TOF MS,1H NMR, solid-state 13C CP/MAS NMR and DFT calculation, and compared it with Zn(II)-curcumin complex. We also used EPR and simulated the results because of the paramagnetic Cu(II). The results indicated that the interacting position of curcumin with Cu(Ⅱ) is its keto-enol H. The interacting ratio of curcumin to Cu(Ⅱ) is 1:1, with the other two ligands-OH and H2O. Cu(Ⅱ) formed square planar-like complex with the four O atoms around. The conjugating system and free-radical scavenging ability of the complex obviously increased compared with curcumin. 4. We use silk fibroin as model to investigate the conformation transition from random coil to (3-sheet under the effect of curcumin, using circular dichroism spectra. The results indicate that low concentration of curcumin has the effect of inducing conformation transition of silk fibroin, and this effect is reduced when curcumin concentration is high.5. We use circular dichroism spectra to investigate the conformation transition from random coil toβ-sheet under the effect of Cu(Ⅱ), with and without curcumin separately. The results indicate that when there is no curcumin, low concentration of Cu(Ⅱ) has the effect of inducing conformation transition of silk fibroin, and this effect is reduced when Cu(Ⅱ) concentration is high; curcumin can reduce the conformation transition of silk frbroin by both chelating Cu(Ⅱ) and producing Cu(Ⅱ)-curcumin complex, from which its treatment on Alzheimer's Disease come.6. We use circular dichroism spectra to investigate the conformation transition from random coil toβ-sheet under the effect of Zn(Ⅱ). with and without curcumin separately. The results indicate that when there is no curcumin, the effect of Zn(Ⅱ) is similar to that of Cu(Ⅱ); curcumin can reduce the conformation transition of silk frbroin by chelating Zn(Ⅱ) and therefore show its treatment on Alzheimer's Disease.