De Novo Antimicrobial Peptides with Low Mammalian Cell Toxicity

Abstract

De novo antimicrobial peptides with the sequences: (KLAKKLA)n, (KLAKLAK)n (where n = 1,2,3), (KALKALK)3, (KLGKKLG)n, and (KAAKKAA)n (where n = 2,3), were prepared as the C-terminus amides. These peptides were designed to be perfectly amphipathic in helical conformations. Peptide antibacterial activity was tested against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Peptide cytotoxicity was tested against human erythrocytes and 3T3 mouse fibroblasts. The 3T3 cell testing was a much more sensitive test of cytotoxicity. The peptides were much less lytic toward human erythrocytes than 3T3 cells. Peptide secondary structure in aqueous solution, sodium dodecylsulfate micelles, and phospholipid vesicles was estimated using circular dichroism spectroscopy. The leucine/alanine-containing 21-mers were bacteriostatic at 3-8 microM and cytotoxic to 3T3 cells at about 10 microM concentrations. The leucine/alanine- or leucine/glycine-containing 14-mers and the leucine/glycine 21-mer were bacteriostatic at 6-22 microM but had much lower cytotoxicity toward 3T3 cells and higher selectivities than the natural antimicrobial peptides magainin 2 amide and cecropin B amide. The 7-mer peptides are devoid of biological activity and of secondary structure in membrane mimetic environments. The 14-mer peptides and the glycine-containing 21-mer show modest levels of helicity in model membranes. The leucine/alanine-containing 21-mer peptides have substantial helicity in model membranes. The propensity to alpha-helical conformation of the peptides in amphipathic media is proportional to their 3T3 cell cytotoxicity.

Learning from cancer how to defeat bacteria

“…What makes AMPs attractive therapeutics is their selective activity against prokaryotes. Earlier studies established that the peptide (KLAKLAK) 2 is a highly effective antibacterial agent with low toxicity (3). Particularly promising is the D (KLAKLAK) 2 (all-D-enantiomer peptidomimetic synthetic version of the designed L-or mixed D/L-peptide), the focus of McGrath et al's article in PNAS (4).…”

Methicillin-dirençli Staphylococcus aureus Bakterilerine Karşı Verbascum thapsus Bitkisinin Anti-Staphylococcal Aktivitesi

“…The data of antibacterial activity were used only when the growth inhibition zone had a diameter ≥10 mm. MICs were determined by microdilution method by adding 100 µL of each strain suspended in Brain Heart Infusion Broth (final concentration 10 5 cfu/mL) to a 96 well micro titer plate with wells containing 100 µL of two fold serial dilutions of extracts (5). The final concentrations of extract were 512 to 8 µg/mL.…”

Modulatory antimicrobial activity of piper arboreum extracts

“…Each inoculum (100 mL) was distributed in each well of a microtiter 96 wells plate and then submitted to a twofold serial dilution using 100 mL of the ethanol extract, with concentrations ranging between 8 and 1024 mg mL -1 . The plates were incubated for 24 hours at 35°C (JAVADPOUR et al 1996). Bacterial MIC was determined using resazurin, with blue changing to red indicating bacterial growth.…”