title: Entropic attraction condenses like-charged interfaces composed of self-assembled molecules.
abstract: Like-charged solid interfaces repel and separate from one another as much as possible. Charged interfaces composed of self-assembled charged-molecules such as lipids or proteins are ubiquitous. The present study shows that although charged lipid-membranes are sufficiently rigid, in order to swell as much as possible, they deviate markedly from the behavior of typical like-charged solids when diluted below a critical concentration (ca. 15 wt %). Unexpectedly, they swell into lamellar structures with spacing that is up to four times shorter than the layers should assume (if filling the entire available space). This process is reversible with respect to changing the lipid concentration. Additionally, the research shows that, although the repulsion between charged interfaces increases with temperature, like-charged membranes, remarkably, condense with increasing temperature. This effect is also shown to be reversible. Our findings hold for a wide range of conditions including varying membrane charge density, bending rigidity, salt concentration, and conditions of typical living systems. We attribute the limited swelling and condensation of the net repulsive interfaces to their self-assembled character. Unlike solids, membranes can rearrange to gain an effective entropic attraction, which increases with temperature and compensates for the work required for condensing the bilayers. Our findings provide new insight into the thermodynamics and self-organization of like-charged interfaces composed of self-assembled molecules such as charged biomaterials and supramolecular assemblies that are widely found in synthetic and natural constructs.
authors.affiliation: The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904 Jerusalem, Israel.
authors.forename: Ariel
authors.initials: A
authors.lastname: Steiner
authors.forename: Pablo
authors.initials: P
authors.lastname: Szekely
authors.forename: Or
authors.initials: O
authors.lastname: Szekely
authors.forename: Tom
authors.initials: T
authors.lastname: Dvir
authors.forename: Roi
authors.initials: R
authors.lastname: Asor
authors.forename: Naomi
authors.initials: N
authors.lastname: Yuval-Naeh
authors.forename: Nir
authors.initials: N
authors.lastname: Keren
authors.forename: Ellina
authors.initials: E
authors.lastname: Kesselman
authors.forename: Dganit
authors.initials: D
authors.lastname: Danino
authors.forename: Roy
authors.initials: R
authors.lastname: Resh
authors.forename: Avi
authors.initials: A
authors.lastname: Ginsburg
authors.forename: Vicky
authors.initials: V
authors.lastname: Guralnik
authors.forename: Esther
authors.initials: E
authors.lastname: Feldblum
authors.forename: Carmen
authors.initials: C
authors.lastname: Tamburu
authors.forename: Menachem
authors.initials: M
authors.lastname: Peres
authors.forename: Uri
authors.initials: U
authors.lastname: Raviv
mesh_terms: D019277:Entropy; D008051:Lipid Bilayers / Q000737:chemistry*; D008055:Lipids / Q000138:chemical synthesis* / Q000737:chemistry; D046911:Macromolecular Substances / Q000138:chemical synthesis / Q000737:chemistry; D013499:Surface Properties
chemical_list: D008051:Lipid Bilayers; D008055:Lipids; D046911:Macromolecular Substances