The Synthetic Peptide P12,P7 Design And IT Bactericidal Activity

Objective: According to the structural characteristics of definite antimicrobial peptides,to design and synthesis of peptides which always have antibacterial activity and study its bactericidal activity.To observe the bactericidal activity of the synthetic peptide under the different factors, And to study the effects of the antibacterial synthetic peptides interact with the commonly used antibiotics,and to provide important information for developing new antibacterial drugs.Methods: From the National Center for Biotechnology Information (National Center for Biotechnology Information, NCBI) Web site ,taking the 13 peptides derived from bovine leukocyte Indolicidin, 21 peptide from insect cells thanatin, 31 peptide from Staphylococcus epidermidis epilancin and 33 peptides from white blood cells hamsters Defensins (defensin) respectively,and taking this 4 kinds of the natural antimicrobial peptides as a reference template for the synthetic antimicrobial peptides. They have the similarity structurally:①These peptides with positive charge (basic), amino acids, no acidic amino acid residues, there are relatively more basic amino acid residues, the five basic amino acids for accounting for 41.7% in the sequences .②This 4 template peptides, except the first peptide linked to only a single basic amino acid residues, others always have least two other basic amino acid residues connected.③They have at least a single basic amino acid residues. According to this similar ground, we have designed a length of 12 amino acid residues peptide, referred to as P12, the sequence is (FYRKMFCKGKKP), 7 amino acid peptide, referred to P7, the sequence is (KRKKRKK). After design, synthesised by the biotechnology company on Haibo Tai. (2): Determination of bactericidal activity:incubated bacteria solution with three different drug concentrations of synthetic peptides interact with the clinical common Gram positive / Gram-negative bacteria, fungi and resistant bacterial at 37℃for 2 hours in water bath, after LB nutrient agar Petri dishes, 37℃overnight cultured 18-20 hours. Counted for each dish on a LB agar colony formed unit (CFU), compared with the control group , calculated bactericidal rate of synthetic peptide .(3): Selecting the stronger bactericidal activity peptide in the three synthetic peptides, analysis of the antibacterial influence factors (PH, Ca2+, Mg2+) .(4): Staphylococcus aureus was treated by the synthetic peptides and antibiotics alone or by the combination of both .utilizing the agar ceiling rate of technological method to evaluate peptide combination bactericidal bactericidal effect.Results: (1): Synthesis of two antimicrobial peptides has a strong bactericidal effect on Gram-positive bacteria Staphylococcus aureus, Bacillus anthracis, Bacillus subtilis, in common with 2h ,synthetic antimicrobial peptide bactericidal concentration (MBC ) between the 8-400ug/ml. Synthesis of two antimicrobial peptides on Gram-negative bacteria are both weak , P12 and P7 had stronger effect on Escherichia coli , after 2 hours in water bath,the MBC 400-1200ug/ml, on the Proteus , Pseudomonas aeruginosa, after 2 hours in water bath, the role of MBC> 1200ug/ml, is relatively weak.. P12 has an strong bactericidal activity against the resistant Staphylococcus aureus and resistant Escherichia coli ,the role of 2 hours in water bath the MBC as 400ug/ml,however,P12 has any sterilization for the Candida albicans. (2): bactericidal activity of synthetic peptides was influenced by the PH of culture medium, and the bactericidal rate were 77.6%, 99.9%, 98.2% in the PH of 5.0; 7.4 and 9.0. In the 2-15mmo1 ? L-1Ca2+,1-70mmo1 ? L-1Mg2+, the most suitable for P7 against Bacillus anthracis. (3): fosfomycin, levofloxacin can enhance the bactericidal activity of P12 ,and erythromycin combine with P12 had no effect on bactericidal activity.Conclusion: 1: The syntheticed antimicrobial peptides followed the natural antimicrobial peptide sequences have antibacterial activity on the gram-positive,It also had good bactericidal activity against drug-resistant Staphylococcus and Escherichia coli.2: The bactericidal activity of synthetic peptides is affected by the PH, Ca2+, Mg2+ effect. It can extrapolation that the mechanism of antibacterial has related to the anion in the bacterial cell .3: Antimicrobial peptides has a synergistic effect with these antibiotics that have cell wall damage function and inhibition DNA synthesis...