TY - JOUR
T1 - Viscosity Landscape of Phase-Separated Lipid Membrane Estimated from Fluid Velocity Field
AU - Sakuma, Yuka
AU - Kawakatsu, Toshihiro
AU - Taniguchi, Takashi
AU - Imai, Masayuki
N1 - Funding Information:
This work was supported by a Japan Society for the Promotion of Science Grant-in-Aid for Young Scientists (B) (Grant Number 17K143681 ).
Publisher Copyright:
© 2020 Biophysical Society
PY - 2020/4/7
Y1 - 2020/4/7
N2 - In cell membranes, the functional constituents such as peptides, proteins, and polysaccharides diffuse in a sea of lipids as single molecules and molecular aggregates. Thus, the fluidity of the heterogeneous multicomponent membrane is important for understanding the roles of the membrane in cell functionality. Recently, Henle and Levine described the hydrodynamics of molecular diffusion in a spherical membrane. A tangential point force at the north pole induces a pair of vortices whose centers lie on a line perpendicular to the point force and are symmetrical with respect to the point force. The position of the vortex center depends on ηm/Rηw, where R is the radius of the spherical membrane, and ηm and ηw are the viscosities of the membrane and the surrounding medium, respectively. Based on this theoretical prediction, we applied a point force to a phase-separated spherical vesicle composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1,2-dioleoyl-sn-glycero-3-phosphocholine/cholesterol by means of a microinjection technique. The pathlines were visualized by trajectories of microdomains. We determined the position of the vortex center and estimated the membrane viscosity using the dependence of the position of the vortex center on ηm/Rηw. The obtained apparent membrane viscosities for various compositions are mapped on the phase diagram. The membrane viscosity is almost constant in the range of 0 < ϕLo ≤ 0.5 (ϕLo: area fraction of the liquid ordered phase), whereas that in the range of 0.5 ≤ ϕLo < 1.0 exponentially increases with increase of ϕLo. The obtained viscosity landscape provides a basic understanding of the fluidity of heterogeneous multicomponent membranes.
AB - In cell membranes, the functional constituents such as peptides, proteins, and polysaccharides diffuse in a sea of lipids as single molecules and molecular aggregates. Thus, the fluidity of the heterogeneous multicomponent membrane is important for understanding the roles of the membrane in cell functionality. Recently, Henle and Levine described the hydrodynamics of molecular diffusion in a spherical membrane. A tangential point force at the north pole induces a pair of vortices whose centers lie on a line perpendicular to the point force and are symmetrical with respect to the point force. The position of the vortex center depends on ηm/Rηw, where R is the radius of the spherical membrane, and ηm and ηw are the viscosities of the membrane and the surrounding medium, respectively. Based on this theoretical prediction, we applied a point force to a phase-separated spherical vesicle composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1,2-dioleoyl-sn-glycero-3-phosphocholine/cholesterol by means of a microinjection technique. The pathlines were visualized by trajectories of microdomains. We determined the position of the vortex center and estimated the membrane viscosity using the dependence of the position of the vortex center on ηm/Rηw. The obtained apparent membrane viscosities for various compositions are mapped on the phase diagram. The membrane viscosity is almost constant in the range of 0 < ϕLo ≤ 0.5 (ϕLo: area fraction of the liquid ordered phase), whereas that in the range of 0.5 ≤ ϕLo < 1.0 exponentially increases with increase of ϕLo. The obtained viscosity landscape provides a basic understanding of the fluidity of heterogeneous multicomponent membranes.
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U2 - 10.1016/j.bpj.2020.01.009
DO - 10.1016/j.bpj.2020.01.009
M3 - Article
C2 - 32053773
AN - SCOPUS:85079381253
VL - 118
SP - 1576
EP - 1587
JO - Biophysical Journal
JF - Biophysical Journal
SN - 0006-3495
IS - 7
ER -