Research On Self Assembly Behavior Of Short Peptide Amphiphiles Of I_mL_nK

Short peptide amphiphiles have been explored as effective nanobiomaterials in applications ranging from controlled gene and drug release, tissue repair, biomineralization and 3D cell culture. Some short peptide amphiphiles show antimicrobial and anticancer effect which has a broad application prospect in cancer therapy. The assembly of short peptide amphiphiles is driven by a series of weak non-covalent forces, such as hydrogen bonding, electrostatic interaction, hydrophobic interaction, Fan Dehua force, aromatic stacking and et. al. Assembly morphology of short peptide amphiphiles include tube, fiber, vesicles and band structure types. By changing the short peptide amphiphiles molecular structure or environment, we can realize the transformation of different assembly type. When short peptide amphiphiles are connected with some functional groups, we can not only make its assembly morphology changes, but also make it have certain function. This paper designed three groups of short peptide amphiphiles with different molecular structures and different number of leucine and isoleucine,but the same amino acid residue number to explore effects of leucine and isoleucine in the role of short peptide amphiphiles assembly. Effect of solvent on the morphology of short peptide amphiphiles assembly was explored by changing the solvent polarity. And the mechanism is discussed here.Experiments show that reducing solvent polarity can make the assembly of I4 K and I3 LK changed from fiber to ribbon, but ILI2K、 I2 LIK and LI3 K assembly unchanged. The possible reason is that reducing the solvent polarity strengthens hydrogen bonding interactions of intermolecular, and the β-sheet second structure of short peptide amphiphiles becomes rigid,this makes it not easy to distort. As a result, ribbon structure forms. Study found that when leucine locates in the N terminal of short peptide amphiphiles, it usually assembles into fiber in 10% acetonitrile solution. However, when the leucine residues are in the middle of short peptide amphiphiles, its assembly morphology is often ribbon structure.Whether short peptide amphiphiles assemble into fibrous or ribbon structure maybe determined by the twisted ability of β-sheet second structure. When the β-sheet second structure is easy to distort, it usully forms fiber structure, instead of the formation of ribbon structure. Leucine residues in N-terminal can promote β-sheet second structure distortion to make it assemble into fiber structure. In the contrary, the leucine residues in the middle of molecules inhibits β-sheet second structure distortion,as a result, ribbon structure forms.