Self-assembly Of Short Functional Amphiphilic Peptides And Their Interaction With Cells

Self-assembly of peptides has aroused great interest in research because of peptide's good biocompatibility and diversity of chemical structure.Most of the peptides studied at present were derived from either the natural protein or by unexpected discovery.It is of great significance and challenge to design the peptides with specific structure and function.Two types of functional peptides were designed and synthesized in the present study.All the peptides have the site that responses to either trypsin or matrix metalloproteinase-7.Their self-assembly behaviors,response to enzyme and interaction with cells were systematically studied.The main contents and conclusions are listed as follows:?1?The results showed that Nap-FFNHCH₂CH₂OCOR₉?Nap-FF-R₉?took random coil in water which did not change with increasing concentration in the studied concentration range.It gave amphorous aggregates in different concentrations.In buffer,the content of random coil decreased while the content of?-sheet increased with increasing the concentration and the regular nanofibers were formed at higher concentrations.?2?The peptide chains of Nap-FF-R₉ can be cleaved by trypsin at the carboxyl side of the arginine residues,and it released the fragment of Nap-FF-NHCH₂CH₂OCO-R?Nap-FF-R?which has strong self-assembling capacity.The addition of trypsin into the solution could significantly alter the self-assembly behavior of the system by producing the longer nanofibers.?3?The MTT results showed that the molecule had high toxicity to both He La cells and NIH 3T3 cells above 55?M.Dyeing experiments proved that the cell membrane damaged,nucleus became pyknotic and cytoskeleton reunited after interaction with Nap-FF-R₉.The experiments of Nap-FF-R₉ interacting with analog membrane showed that electrostatic interaction may have greater impact in the process of damage to cell membrane.The interaction of I₃G₃R₉ and R₉ obtained by adjusting the amino acid residues of Nap-FF-R₉ with cells showed that the amphiphilicity was possibly an important factor to induce cells death.?4?The secondary structure of Nap-FFGPLGLARK in water,Nap-FFKPLGLARK and Nap-FFGPLGLARKRK in water and buffer transformed random coil into?-sheet with the increase of concentration.The self-assembled structure of them also changed from amphorous aggregates to regular fibers with concentration increase.Since the solubility of Nap-FFGPLGLARK in buffer solution was very small,which limited its research.?5?Nap-FFGPLGLARK,Nap-FFKPLGLARK and Nap-FFGPLGLARKRK all contain the fragment of-PLGL-,and the amide bond between glycine and leucine was cleaved when interacting with MMP-7 to release Nap-FFGPLG,Nap-FFKPLG and Nap-FFGPLG.When MMP-7 was added,the morphology of products of Nap-FFGPLGLARK had no significant change because of the low conversion rate,and the products of Nap-FFKPLGLARK further assembled into longer nanofibers.In the case of Nap-FFGPLGLARKRK,after MMP-7 was added,the products formed thinner fibrils.These fibrils could assemble into wider fiber bundles which were similar to crystals.?6?By assessing the interaction of Nap-FFKPLGLARK with He La cells,NIH 3T3 cells,Staphylococcus aureus,Escherichia coli,Bacillus subtilis and Pseudomonas aeruginosa,it was found that Nap-FFKPLGLARK can selectively kill Staphylococcus aureus at the concentration of 100?M.Nap-FFGPLGLARKRK was not toxic to He La cells,NIH 3T3 cells at low concentration and can kill them all at high concentration.