Abstract
Biomimetic and biological membranes consist of molecular bilayers with two leaflets which are typically exposed to different aqueous environments and may differ in their molecular density or composition. Because of these asymmetries, the membranes prefer to curve in a certain manner as quantitatively described by their spontaneous curvature. Here, we study such asymmetric membranes via coarse-grained molecular dynamics simulations. We consider two mechanisms for the generation of spontaneous curvature: (i) different lipid densities within the two leaflets and (ii) leaflets exposed to different concentrations of adsorbing particles. We focus on membranes that experience no mechanical tension and describe two methods to compute the spontaneous curvature. The first method is based on the detailed structure of the bilayer's stress profile which can hardly be measured experimentally. The other method starts from the intuitive view that the bilayer represents a thin fluid film bounded by two interfaces and reduces the complexity of the stress profile to a few membrane parameters that can be measured experimentally. For the case of asymmetric adsorption, we introduce a simulation protocol based on two bilayers separated by two aqueous compartments with different adsorbate concentrations. The adsorption of small particles with a size below 1 nm is shown to generate large spontaneous curvatures up to about 1/(24 nm). Our computational approach is quite general: it can be applied to any molecular model of bilayer membranes and can be extended to other mechanisms for the generation of spontaneous curvatures as provided, e.g., by asymmetric lipid composition or depletion layers of solute molecules.
Highlights
The basic building blocks of both biological and biomimetic membranes are lipid bilayers consisting of two lipid monolayers or leaflets.1 Biological membranes are asymmetric in the sense that their two leaflets differ in their lipid composition.2 This bilayer asymmetry has been recently mimicked in synthetic lipid bilayers produced by different preparation methods.3,4 In addition, the two sides of the bilayer membranes are typically exposed to aqueous solutions that differ in their ionic or molecular composition
As shown by our present study, the Gibbs adsorption equation, which follows from the thermodynamics of liquid-liquid interfaces, can be applied to the adsorption onto the two leaflet-water interfaces bounding the bilayer membrane if we identify the tension of such an interface with the mechanical tension within the corresponding bilayer leaflet
We have used coarse-grained molecular dynamics simulations to determine the spontaneous curvature of bilayer membranes
Summary
The basic building blocks of both biological and biomimetic membranes are lipid bilayers consisting of two lipid monolayers or leaflets. Biological membranes are asymmetric in the sense that their two leaflets differ in their lipid composition. This bilayer asymmetry has been recently mimicked in synthetic lipid bilayers produced by different preparation methods. In addition, the two sides of the bilayer membranes are typically exposed to aqueous solutions that differ in their ionic or molecular composition. Such a layer should have a tendency to bend or bulge towards the interface with the lower tension, because the layer can reduce the area of the other interface with the higher tension Based on this intuitive picture, one can develop an analytical theory for the preferred or spontaneous curvature of bilayer membranes when their two leaflets are exposed to different concentrations of adsorbing particles.. We start from the intuitive view of spontaneous curvature arising from different tensions of the two leaflet-water interfaces We reconsider these tensions and define them in terms of the mechanical tensions acting within the two leaflets of the bilayer membrane. We give a brief outlook on the generality of our approach and on its applicability to other mechanisms for the generation of spontaneous curvature
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
