Anion hopping of (and on) functional oligoarginines: from chloroform to cells

Rapid progress in the understanding of counteranions as either activators or inactivators of guanidinium-rich macromolecules is summarized. From phase transfer of polyarginine into chloroform to the cytosolic delivery of green-fluorescent proteins or apoptosis-inducing peptides with cell-penetrating peptides, counteranions emerge consistently as the origin of function. A unified view of this "demystified arginine magic" is proposed, focusing on the manipulation of the underlying anion hopping of and on these sticky molecular chameleons according to the principle of Le Chatelier.