How a few help all: cooperative crossing of lipid membranes by COSAN anions
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Updated: Jul 13, 2025

Lipid Bilayer Experiments with Contact Bubble Bilayers for Patch-Clampers
Published on: January 16, 2019
David C Malaspina1, Francesc Teixidor1, Clara Viñas1
1Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, E- 08193, Bellaterra, Spain. clara@icmab.es.
Abstract:
Experimental results show that the presence of a concentration gradient of certain nano-ions (most notably cobaltabisdicarbollide ([o-COSAN]- anions), induce a current across intact artificial phospholipid bilayers in spite of the high Born free energy estimated for these ions. The mechanism underlying this observed translocation of nano-anions across membranes has yet to be determined. Here we show, using molecular dynamics simulations, that the permeation of [o-COSAN]- anions across a lipid bilayer proceeds in a cooperative manner. Single nano-ions can enter the bilayer but permeation is hampered by a free energy barrier of about 8kBT. The interaction between these nano-ions inside a leaflet induces a flip-flop translocation mechanism with the formation of transient, elongated structure inside the membrane. This cooperative flip-flop allows an efficient distribution of [o-COSAN]- anions in both leaflets of the bilayer. These results suggest the existence of a new mechanism for permeation of nano-ions across lipid membranes, relevant for those that have the appropriate self-assembly character.
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