The influence of anisotropic inclusions on curvature elastic properties of lipid membranes

Miha Fošnarič^1, Veronika Kralj-Iglič^2, Klemen Bohinc^3, Dorit R. Gauger, Sylvio May^4, Aleš Iglič^1

1^Group of Applied Physics, Faculty of Electrical Engineering, University of Ljubljana; 2^Institute of Biophysics, Faculty of Medicine, University of Ljubljana; 3^UCHS , University of Ljubljana; 4^Department of Physics, NDSU, Fargo N.D.

Rigid inclusions can be viewed as simple models for membrane-penetrating or integral proteins and peptides. We suggest a theoretical model that allows to estimate their influence on the curvature elastic properties of lipid membranes. Our treatment includes anisotropic inclusions whose energetics depends on their in-plane orientation within the membrane. On the basis of continuum elasticity theory, we calculate the inclusion-membrane interaction constants that reflect the inclusion-induced, short-ranged, elastic deformation of a bent lipid layer. A numerical estimate of the interaction constants indicates the ability of inclusions to sense membrane bending and to accumulate at regions of favorable curvature, matching the shape of the inclusions. We also show that isotropic and anisotropic inclusions have opposing tendencies: the former rigidify and the latter soften the membrane. Strongly anisotropic inclusions interact favorably with lipid layers that adopt saddle-like curvature; such structures may be stabilized energetically. We explore this possibility for the case of vesicle budding, where we consider a shape sequence of closed, axisymmetric vesicles that form a (saddle-curvature adopting) membrane neck. It appears that not only isotropic but also strongly anisotropic inclusions can significantly contribute to the budding energetics, a finding which we discuss in terms of recent experiments.

Email: miha.fosnaric@fe.uni-lj.si

Address: Miha Fošnarič, Group of Applied Physics, Faculty of Electrical Engineering, University of Ljubljana, Tržaška 25, SI-1000 Ljubljana, Slovenia