Antibiotic Properties of Cationic Amphipathic α-helix Peptide Sequences
Greenberger, Virginia Rose
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Antibiotic resistance continues to pose a threat to the human race as bacteria become more and more resistant to antibiotics. New multidrug resistant (MDR) strains of tuberculosis, methicillin-resistant staphlococcus aureus (MRSA), and vancomycin resistant enterococci (VRE), amongst other bacteria, are causing expensive, painful and deadly diseases (Nikaido 2009). A need for new antibiotics to treat these infections has fueled scientists to revisit studying antimicrobial peptides (AMPs). AMPs, derived from a wide variety of natural sources, are categorized by their shape. In this project we investigated the ability of a series of cationic, amphipathic , α-helical peptides derived from sequences within nitric oxide synthases (NOS) to inhibit growth of E. coli and S. aureus. Cell growth in the presence and absence of peptide were monitored as a change in optical density (OD) of a culture at 600 nm. Assays to determine the minimun inhibitory concentrations (MIC) were also conducted, and the peptides’ ability to rupture cell membranes were assessed by measuring the rise in fluorescence of a solution containing dye encased liposomes. The result show that the peptide derived from the inducible NOS was neither bacteriocidal at the concentrations tested nor did it cause leakage of the liposomes, while the peptide derived from the neuronal NOS was bacteriocidal to both E. coli and S. aureus, but also did not cause liposome leakage. These results are encouraging as potential starting points in the search for new agents that can be used as antibacterial agents.