AVS 56th International Symposium & Exhibition
    Applied Surface Science Thursday Sessions
       Session AS2+BI-ThM

Paper AS2+BI-ThM11
Effect of Different Cations on the Nanomechanical Response of a Model Phospholipid Membrane : A Force Spectroscopy Study

Thursday, November 12, 2009, 11:20 am, Room K

Session: Scanning Probe Studies of Biological Materials
Presenter: L. Redondo-Morata, University of Barcelona, Spain
Authors: L. Redondo-Morata, University of Barcelona, Spain
G. Oncins, University of Barcelona, Spain
F. Sanz, University of Barcelona, Spain
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Understanding the effect of mechanical stress on biological membranes is of fundamental importance in biology since cells are known to naturally perform their function under the effect of a complex combination of forces. The chemical composition of such membranes is the ultimate responsible for determining the cellular scaffold, closely related to its function. Nevertheless, there is another factor that has been widely discussed in theoretical works but never experimentally tested in an accurate way, which is the presence of ions and their nature (radius and charge) on the stability of the bilayers. Micro-scale assays have revealed a wealth of information regarding the overall membrane mechanical resistance. Nonetheless, the diversity in the chemical composition of such membranes makes it difficult to individually probe the mechanical contribution of every particular membrane component. Here we use force spectroscopy to quantitatively characterize the nanomechanical resistance of supported lipid bilayers as a function of ionic strength and the composition of the electrolyte thanks to a reliable molecular fingerprint that reveals itself as a repetitive jump in the approaching force curve, hallmark of bilayer rupture. By systematically testing a set of bilayers composed of different phospholipids immersed in electrolytes composed of a variety of monovalent and divalent cations, we first show that the cationic radius, its charge density and the hydration number have an independent and important contribution to the overall bilayer mechanical stability. This work opens up avenues for characterizing the membrane (nano)mechanical stability and to assess the effect of different ions in the structure of the bilayers in an experimental and reproducible way.