Optimizing antifungal properties of tetrabranched peptide B4010.

B4010 is a new tetrabranched antifungal peptide that depolarizes and permeabilizes the cytoplasmic membrane. However, the role of the different amino acid components is not clear. It was hypothesized that alanine scanning, a method of replacing each amino acid with alanine, could identify the amino acid residues responsible for antifungal and hemolytic activities. The alanine mutants were tested in their ability to inhibit three Candida strains, alter membrane potential measured by DiSC35 assay and hemolyse red blood cells. Residues in the 1st, 3rd, 6th and 8th position were critical for antifungal activity as substitution caused a decrease in the antifungal activity. The 4th and 5th residues were non-essential as there was no change in the antifungal activity compared to B4010. The antifungal response for the 2nd residue substitution differs among three strains of Candida. The alanine substitution for the 7th residue had the best MIC99 at 1.48 µM against C. albicans ATCC strain. All peptides displayed low hemolytic activity compared to B4010. B4010 had the highest depolarization among the peptides but not the best antifungal activity, implying other factors contribute to antifungal action. By this approach we obtained an activity-toxicity profile that enabled us to design therapeutically important antifungal peptides.Bachelor of Science in Biological Science