Direct observation of anion-mediated translocation of fluorescent oligoarginine carriers into and across bulk liquid and anionic bilayer membranes.

The recent hypothesis that counteranion-mediated dynamic inversion of charge and solubility might contribute to diverse functions of oligoarginines in biomembranes was tested with two fluorescently labelled oligomers, FL-R(8), one of the most active cell-penetrating peptides, and its longer version, FL-R(16). We report evidence for counteranion-mediated phase transfer from water into bulk chloroform and anionic lipid-bilayer membranes as well as reverse-phase transfer from bulk chloroform and across intact lipid-bilayer membranes into water. The differences found between FL-R(8) and FL-R(16) with regard to location in the bilayer and reverse-phase transfer from bulk and lipid-bilayer membranes into water implied that the reported results may be relevant for biological function.