Psacotheasin is a 34-mer knottin-type peptide that is derived from Psacothea hilaris larvae In this study, the antifungal activity and mechanism(s) by which psacotheasin affects human fungal pathogens were investigated Psacotheasin shows remarkable antifungal properties without hemolytic activity against human erythrocytes To understand the antifungal mechanism(s) of psacotheasin in Candida albicans, flow cytometric analysis with DiBAC(4)(3) and PI was conducted The results showed that psacotheasin depolarized and perturbed the plasma membrane of the C albicans Three-dimensional (3D)-flow cytometric contour-plot analysis, accompanied by decreased forward scatter (FS), which indicates cell size, confirmed that psacotheasin exerted antifungal effects via membrane permeabilization The membrane studies, using a single GUV and FITC-dextran (FD) loaded twosomes, indicate that psacotheasin acts as a pore-forming peptide in the model membrane of C albicans and the radius of pores were presumed to be anywhere from 2 3 to 3 3 nm Therefore, the current study suggests that the mechanism(s) of psacotheasin's antifungal properties function within the membrane (C) 2010 Elsevier Inc All rights reserved.