Asymmetric Lipid Membranes under Shear Flows: A Dissipative Particle Dynamics Study

Abstract

We investigate the phase behavior of the asymmetric lipid membranes under shear flows, using the dissipative particle dynamics simulation. Two cases, the weak and strong shear flows, are considered for the asymmetric lipid microstructures. Three typical asymmetric structures, the membranes, tubes, and vesicle, are included in the phase diagrams, where the effect of two different types of lipid chain length on the formation of asymmetric membranes is evaluated. The dynamic processes are demonstrated for the asymmetric membranes by calculating the average radius of gyration and shape factor. The result indicates that different shear flows will affect the shape of the second type of lipid molecules; the shape of the first type of lipid molecules is more stable than that of the second type of lipid molecules. The mechanical properties are investigated for the asymmetric membranes by analyzing the interface tension. The results reveal an absolute pressure at the junctions of different types of particles under the weak shear flow; the other positions are almost in a state of no pressure; there is almost no pressure inside the asymmetric lipid membrane structure under the strong shear flow. The findings will help us to understand the potential applications of asymmetric lipid microstructures in the biological and medical fields.

Self-Assembly of Lipid Mixtures in Solutions: Structures, Dynamics Processes and Mechanical Properties

“…Since the dynamics process depends on the processing pathway [ 56 ], the initial state can affect the dynamics process during the self-assembly of lipid molecules. Usually, we input several different initial structures, such as the lamellar and spherical structures, as well as the random inputting, for a given system parameter set in the simulations.…”

Simulations of morphology control of self‐assembled amphiphilic surfactants

“…At the individual molecule level, DPD simulations by Chen et al suggest that different values of the external flow rate can have a significant impact on the radius of gyration of individual amphiphiles, thus changing the local spontaneous curvature of bilayer structures. 200 Aggregate bilayer assembly behavior in shear flow parallel to the bilayer was more systematically investigated using CGMD by Hanasaki et al 201 With an increasing shear rate, the microscopic structures shift from slight tilting in the shear direction, to buckling, to a Kelvin-Helmholtz-like instability with swirling patterns, eventually leading to the collapse of the bilayer structure. The instability is due to a significant shear flow velocity gradient across the normal direction of the bilayer that pulls apart the individual amphiphiles.…”

“…It is insightful to first examine how flat bilayers respond to external shear flow as a basis for understanding deformation mechanisms and shape stability of vesicles. At the individual molecule level, DPD simulations by Chen et al suggest that different values of the external flow rate can have a significant impact on the radius of gyration of individual amphiphiles, thus changing the local spontaneous curvature of bilayer structures 200 . Aggregate bilayer assembly behavior in shear flow parallel to the bilayer was more systematically investigated using CGMD by Hanasaki et al 201 With an increasing shear rate, the microscopic structures shift from slight tilting in the shear direction, to buckling, to a Kelvin‐Helmholtz‐like instability with swirling patterns, eventually leading to the collapse of the bilayer structure.…”

Self-Assembly of Lipid Molecules under Shear Flows: A Dissipative Particle Dynamics Simulation Study

“…The expression for the bending force is where , , and are the bending constant, equilibrium angle, and tilt angle, respectively. In our simulations, we set and , which is consistent with previous DPD simulations [ 44 , 61 ]. Here, we note that the elastic harmonic force and bending force exist in the lipid chains to maintain the connectivity and rigidity of chains, which are different from the DPD forces in Equation ( 1 ).…”

“…The reverse nonequilibrium method (RNEMD) is a widely used approach for calculating shear viscosity by connecting shear fields and transverse linear momentum fluxes [ 14 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 ]. In our simulations, we employed RNEMD to generate shear flow, as shown in Figure 1 b.…”