The Investigation Of Aggregation And Conformation Change Of Silk Protein In Solution

Because of its excellent comprehensive mechanical properties and bio-compatibilities, Silk, as on kind of nature animal fiber, has widely applications and potentials in the fields of textile, defense, medicine, food and cosmetic industry. Its formation mechanism and conformation change attract many attentions in the scientific area.The current thesis investigates the integrity of silk fibroin extracted from solid silk fiber and silkworm gland by the measurement of protein molecular weight using SDS-PAGE. The results indicate that the regeneration process of silk fibroin for solid silk fiber will result in partial degradation, which depends on the temperature, time, degumming and dissolving agent. Furthermore, the silk fibroin extracted from the middle division of silkworm gland is intact and No degradation can be observed. The posterior division content, however, has many impurities.Circular Dichroism Spectrometer (CD) and Fluorescence Spectrometer (FS) have been used to monitor the conformation change of regenerated silk fibroin (RSF) in aqueous solution. CD results suggest that RSF undergoes a conformation transition from random coil to P-sheet. The transition kinetics consists two different rate sections. The blue shift of Tryptophan (Trp) emission peek indicates that a micro-environment change occur during the conformation transition.Gland Silk Fibroin (GSF) solution conformation transition and aggregation have been investigated by the combination of CD, FS and Dynamic Light Scattering (DLS). Similar as the CD and FS results of RSF, the conformation change from random coil toβ-sheet and micro-environment change of Trp residue can be observed from GSF solution by CD and FS. With increasing the protein concentration, the transition speed increase. The whole transition kinetics can be divided to three individual sections: induction, growth and stabilization. Accompanied with protein conformation change, the aggregation of protein molecules has been proved by DLS to a final size of 2μm.