Recently, great attention has been devoted to viruses; in fact, many viruses have evolved quite efficient systems for endosomal release.8 Therefore, the discovery of new methodologies to reproduce their behavior represents a key objective. Since viruses may enter cells either through a endosomal pathway or via direct fusion on the plasma membrane through the activity of membranotropic peptides, great attention has been devoted to the study of hydrophobic peptides that traverse biological membranes efficiently, promoting lipid-membrane reorganizing processes such as fusion or pore formation and involving temporary membrane destabilization and subsequent reorganization,7,9 which may be able to circumvent the endosomal entrapment by favoring the escape from the endosome or by translocating a cargo through the plasma membrane directly into the cytosol. Delivery across cellular membranes involves several mechanisms, such as direct transfer through the cell surface membrane by lipid membrane fusion or transient permeabilization of the cell membrane. Alternatively, following endocytosis, transfer across vesicular membranes by lipid disruption, pore formation, or fusion may take place. Several of these membrane reorganization steps are also involved in the cell entry of viruses and other microorganisms, as well as being triggered by protein toxins and defense peptides.10 Several related processes, such as intracellular vesicle budding, cell-to-cell fusion,9 sperm-egg fusion, and the immune response, share common features with the mechanism of viral-induced membrane fusion.