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.
Subject(s)
Anti-Bacterial Agents/pharmacology , Bacteria/drug effects , Cell Survival/drug effects , Peptides/pharmacology , 3T3 Cells , Amino Acid Sequence , Animals , Anti-Bacterial Agents/chemistry , Circular Dichroism , Erythrocytes/drug effects , Escherichia coli/drug effects , Humans , Liposomes , Mice , Micelles , Microbial Sensitivity Tests , Molecular Sequence Data , Peptides/chemistry , Protein Structure, Secondary , Pseudomonas aeruginosa/drug effects , Sodium Dodecyl Sulfate , Staphylococcus/drug effectsABSTRACT
Lower limb fractures occurring in patients with established spinal paralysis were considered different enough to warrant variations in treatment usually provided to patients without paralysis. Treatment should ensure that functional level will be unchanged after healing occurs. Splints made of soft materials were effective, inexpensive, safe, and allowed for good healing with early rehabilitation.
