A Study On Methods Of Antimicrobial Peptides Rapid Selection And Antimicrobial Activity

Depending on the peptide–membrane interaction mechanisms of antimicrobial peptides, investigate a method which can rapid select antimicrobial peptides. Using Liquid Chromatography-mass Spectrometry to compare with the spectrum before and after extract incubated with E.coli, collect the peaks which are disappeared. The results indicated that compared with the spectrum before and after extract incubated with bacteria can provided a rapid and direct method for identification of antimicrobial peptides. Using two different materials which from insect and plant to validate this method.Compare with the spectrum of UPLC before and after extract incubated with E.coli respectively from housefly larvae protein and fermented soybean protein by Lactobacillus plantarum LP6, the disappear peptides named HLP7,HLP8,FSP6,FSP8,FSP9. All the peptides was purified by RP-HPLC. The antibacterial assay of these peptides showed that only the peptides which are disappeared can effectively inhibited the growth of bacterial pathogens Escherich coliATCC25922, Bacteriump yocyaneum ATCC 27553, Salmonella typhimurium 50013, Shigella dysenteriae, Staphylococcus aureus 6538 and Bacillus subtilis 9372, and Escherich coli JM109. The method can be rapid select antimicrobial peptides from two materials, this method can greatly reduce the experimental period.The antimicrobial activity results of different HPLC fractions from larvae protein and fermented soybean protein showed that antimicrobial activities will increased when their average hydrophobicity increased. The sequences of these peptides were identified by MAFSPI-TOF/TOF-MS, the result are KPPLNGPAL,QPVYHWYWH,VVTSSSLP,RMRLLLRRKGGQ and RVLLLPAFAEK , all these peptides maybe new antimicrobial peptides, and the possible reasons of the components which was not disappeared did not have antimicrobial activity, were the average grand average hydrophobicity value is too low, did not have enough positive charge, or the hydrophobicity and charge number was not in a balance.Calculate the grand average hydrophobicity value of 103 known antimicrobial peptides, most average hydrophobicity are located in -1.0～0.01, the range of Hydrophobic residue% is 10%-70%,most belong to 30%-60%.Although the number of net charge is not regular, when the length of peptides increased, positive net charge significantly increased too (P <0.01). What's more, different mechanisms require different number of positive net charge.The correlation analysis of 103 known antimicrobial peptides showed that there was significant negative correlation between grand average hydrophobicity value and positive net charge (P<0.001, r =-0.47138), both of them play very important roles in peptide–membrane interactions. Most of the antimicrobial peptides have high hydrophobic value. The acetonitrile percentage of five peptides which separated from larvae protein and fermented soybean protein are 40%, 43%, 39%, 46.5% and 50%, the ratio of hydrophobic residues in the 30% -50%, this result showed that all of them have high hydrophobic , which are as same as other antimicrobial peptides.