Research Of The Interaction Between Phospholipids And New Type Antimicrobial Peptides

The most important property of antimicrobial peptide is their special sterilization mechanism. The antimicrobial peptide mainly targets the backbone of bacterial cell membrane-phospholipid bilayer. Because DMPC and DMPG are the main phospholipids to constitute the membrane of flora and fauna and bacterium respectively, the DMPC and DMPG are used to simulate the flora and fauna and bacterium cell membrane to investigate the interaction between antimicrobial peptides with different phospholipids. Three groups of antimicrobial peptides are designed in this research. The interaction between these three groups peptide and phospholipids are investigated by electrochemistry, fluorescence quenching and compute simulation method. The results are as follows.The sequences KFNFK, KFSFK, KFTFK were chosen in the first group as single bioactive sequence, and according to these sequences, linear and cyclic peptides with dual bioactive sequences were designed and the interaction between peptides and phospholipids were studied. The result of compute simulation showed that peptides with dual bioactive sequences could offer more positive charged amino acids than short peptides with single bioactive sequence to facilitate the electrostatic attraction with negative charged head group of DMPG, which leads to higher binding energy with DMPG for linear and cyclic peptides. Because of the rigid configuration and short sequence of cyclic peptides, so they have a lower binding energy with DMPG compared to linear peptides. The interaction between peptides and phospholipid was further investigated by electrochemistry method by using solid supported bilayer as membrane mimic. The results showed that peptides with dual bioactive sequences have a higher destructive effect against phospholipid bilayer than peptide with single bioactive sequence regardless of DMPC or DMPG. The influence of peptides concentration on the interaction with DMPG was more sensitive than DMPC.RRWWRF and FRWWHR which are from antimicrobial peptides database were chosen as single bioactive sequences for designing linear and cyclic antimicrobial peptides with dual bioactive sequences, and their interaction with phospholipids was further investigated. Compute simulation results showed that peptides with dual bioactive sequences had a higher binding energy with DMPG than peptides with single bioactive sequence, which indicates that peptides with dual bioactive sequences are easier to bind to DMPG. The electrochemistry experiment results showed that this second group peptide couldn’t destruct DMPG membrane though they had a destructive effect to DMPC. So we deduced that the second group peptides could interact with bacterial cell membrane, enter the interior of cell, interact with the substance in cell and finally kill the bacterium, instead of disrupting cell membrane.Peptides with single bioactive sequence and dual bioactive sequences using RFTFR, RWTWR, KWTWK as bioactive segments has been designed and their interaction with phospholipids was further studied. The compute simulation results showed that linear peptides with dual bioactive sequences had higher binding energy than peptides with single bioactive sequence, indicating a stronger binding of linear peptides with DMPG. The electrochemistry experiment results showed that peptides with dual bioactive sequences could disrupt DMPC or DMPG membrane while peptides with single bioactive sequence hardly disrupt phospholipid membrane. Peptides showed stronger disrupting ability on DMPG membrane compared to DMPC membrane. The results of fluorescence quenching experiment showed that short peptides hardly inserted into DMPC or DMPG lipsomes. However linear peptides could inserted into DMPG lipsomes but nearly have no interaction with DMPC.