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Structural studies of fusion peptide from tick-borne encephalitis virus and nanocrystalline cellulose films Pan, Jinhe

Abstract

This thesis describes structural studies on two different systems, namely the fusion peptide (FP) from the tick-borne encephalitis virus (TBEV) and nanocrystalline cellulose (NCC). The first is a small biopolymer composed of 16 amino acid residues, which binds to the target cell membrane and plays a critical role in membrane fusion. The second is a biopolymer composed of a large number of glucose subunits, which has attracted recent interest with regards to the development of new materials. In this thesis, I have established synthetic access to the model FP fragment from TBEV. To our knowledge, the studies in this thesis are the first investigation on the individual Class II FP. The synthetic peptide can induce membrane fusion at acidic pH. Mutational studies showed that replacement of Leu 107 with Thr strongly impaired fusogenic activity, whereas a Phe mutant still retained a significant degree of activity. These results were consistent with activity found in mutant TBE viruses, indicating that the synthetic TBEV FP obtained here can serve as a model fusion system. Previous literature studies have shown that a disulfide bond stabilizes the peptide fold and the full length fusion protein functions as a trimer. I therefore tested the hypothesis that these are also necessary conditions for the FP. The studies on the modified FPs suggest that the lipid-binding portion in the synthetic peptides adopts a similar conformation. However, the disulfide bond promotes β-strand formation in the peptide. Finally, the formation of an artificial trimer enhances the fusogenic activity. In the second part of this thesis, the chiral nematic structure and crystallinity of the NCC films were investigated. The chiral nematic pitch of the NCC films was affected by all of the parameters listed here, namely the hydrolysis conditions, ionic strength, suspension concentration, drying temperature and magnetic field. The crystallinity of the NCC films was influenced by the drying temperature, ionic strength and magnetic field were small. These results suggest that these sample conditions affect the chiral nematic structure and the crystallinity of the NCC films, a finding which will be important in the development of novel cellulosic materials.

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