Entropic force between biomembranes

Abstract

Undulation force, an entropic force, stems from thermally excited fluctuations, and plays a key role in the essential interactions between neighboring surfaces of objects. Although the characteristics of the undulation force have been widely studied theoretically and experimentally, the distance dependence of the force, which constitutes its most fundamental characteristic, remains poorly understood. In this paper, first, we obtain a novel expression for the undulation force by employing elasticity and statistical mechanics and prove it to be in good agreement with existing experimental results. Second, we clearly demonstrate that the two representative forms of the undulation force proposed by Helfrich and Freund were respectively the upper and lower bounds of the present expression when the separation between membranes is sufficiently small, which was intrinsically different from the existing results where Helfrich's and Freund's forms of the undulation force were only suitable for the intermediate and small separations. The investigations show that only in a sufficiently small separation does Helfrich's result stand for the undulation force with a large wave number and Freund's result express the force with a small wave number. Finally, a critical acting distance of the undulation force, beyond which the entropic force will rapidly decay approaching zero, is presented.

Interplay of receptor-ligand binding and lipid domain formation during cell adhesion

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Engineering surface patterns on nanoparticles: new insights into nano-bio interactions

“…32 Many life activities in nature are closely related to this, such as virus infection, cell migration, vesicle transportation, and fertilization. 33 Due to the different chemical properties and physical states of different proteins and lipids on the membrane, based on hydrophobic interactions, electrostatic interactions, van der Waals forces, hydrogen bonds and hydration forces, the membrane surface will form a variety of synergistic lipid raftprotein structure domains (surface pattern). These surface patterns are critically important in mediating life activities.…”

“…32 Many life activities in nature are closely related to this, such as virus infection, cell migration, vesicle transportation, and fertilization. 33…”

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