[A group of synthetic antimicrobial peptides].

Cecropin A1 (CA), first found in the diapause pupa of Hyalophora cecropia, is an alpha-helix antimicrobial peptide. It has suppressive effect on several strains of bacteria but its effect is moderate. Therefore it is imperative to find new peptides of high lethality to pathogenic bacteria. The structure of CA was modified by increasing its alpha-helix number to improve the antimicrobial activity on the basis of previous works that there is a close relationship between the alpha-helix status of peptide and its antimicrobial activity. Fifteen peptides (GK1-GK15) containing the 1st to 8th amino acids (KWKLFKKI) at N terminus of CA linking with a typical alpha-helix structure by GIG hinge were synthesized. Purity (97%) of GK-8 was confirmed by HPLC and molecular weight (2934.0 Da) was measured by mass spectrometry. Minimum inhibitory concentration (MIC, microg/mL) was used to compare their killing efficiency on various bacteria both Grams-positive and Grams-negative. The results showed the killing efficiency of the modified peptides (GK-1, GK-2, GK-8, GK-10) on various bacteria were much more effective than the original and their MICs were only one percent (0.25 microg/ mL) of CA and magainin. It indicates that typical core alpha-helix of the peptides is essential for their lethality to pathogens and some of modified peptides can serve as attractive candidates for antimicrobial drug discovery. The patent number is PCT/ CN 03/00522.