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Nanomechanics of multiple units in the erythrocyte membrane skeletal network.

de Oliveira M, Vera C, Valdez P, Sharma Y, Skelton R, Sung LA - Ann Biomed Eng (2010)

Bottom Line: While actin protofilaments remain tangent to the network, their yaw (Phi) angles change drastically with addition of neighboring units or an Sp unfolding.It is anticipated that during deformation, transmembrane complexes associated with the network move laterally through the lipid bilayer and increase the diffusion of molecules across the membrane.When protofilament/Sp sweeps under the lipid bilayer, they mix up the submembrane concentration gradient.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, 92093, USA.

ABSTRACT
Erythrocytes undergo deformations when they transport O(2) and CO(2) across the membrane, yet the 3D nanomechanics of the skeletal network remains poorly understood. Expanding from our previous single isolated unit, we now simulate networks consisting of 1-10 concentric rings of repeating units in equibiaxial deformation. The networks are organized with (1) a 3D model for a single unit, (2) a wrap-around mode between Sp and actin protofilament in the intra-unit interaction, and (3) a random inter-unit connectivity. These assumptions permit efficient five-degrees-of-freedom (5DOF) simulations when up to 30 pN of radial forces are applied to the boundary spectrin (Sp) and the center and other units are analyzed. As 6 Sp balance their tensions, hexagonal units become irregular. While actin protofilaments remain tangent to the network, their yaw (Phi) angles change drastically with addition of neighboring units or an Sp unfolding. It is anticipated that during deformation, transmembrane complexes associated with the network move laterally through the lipid bilayer and increase the diffusion of molecules across the membrane. When protofilament/Sp sweeps under the lipid bilayer, they mix up the submembrane concentration gradient. Thus, the nanomechanics of actin protofilaments and Sp may enhance the transport of molecules during erythrocyte deformation.

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Related in: MedlinePlus

Deformation of erythrocytes in microcirculation and the network nanomechanics. (a) Erythrocytes deform (from their biconcave disk shape) extensively in microcirculation where gas exchange occurs in tissue capillaries.30 The flow is from left to right. (b) The dynamics of the membrane skeleton (e.g., the tension in Sp and the attitude of the protofilament) underneath the lipid bilayer may have a pivotal role in transport phenomena, facilitating the movement of some molecules through the lipid bilayer and protein carriers during membrane deformation. The presence of a JC (junctional complex), Sp (spectrin), and SC (suspension complex) in the middle of a Sp tetramer represents two SCs from adjacent units. The pointed end of the protofilament is marked with erythrocyte tropomodulin (E-Tmod, a sphere)
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Fig1: Deformation of erythrocytes in microcirculation and the network nanomechanics. (a) Erythrocytes deform (from their biconcave disk shape) extensively in microcirculation where gas exchange occurs in tissue capillaries.30 The flow is from left to right. (b) The dynamics of the membrane skeleton (e.g., the tension in Sp and the attitude of the protofilament) underneath the lipid bilayer may have a pivotal role in transport phenomena, facilitating the movement of some molecules through the lipid bilayer and protein carriers during membrane deformation. The presence of a JC (junctional complex), Sp (spectrin), and SC (suspension complex) in the middle of a Sp tetramer represents two SCs from adjacent units. The pointed end of the protofilament is marked with erythrocyte tropomodulin (E-Tmod, a sphere)

Mentions: Understanding the relationship between the structure of the cell membrane and its mechanical properties will be an important endeavor in cell biology and bioengineering in the next decade.8 An erythrocyte offers the simplest model to study cell membranes as it consists of only a lipid bilayer and an underlying protein skeleton. It is this structure that allows erythrocytes to repeatedly squeeze through small capillaries without compromising their structural integrity (Fig. 1a).FIGURE 1


Nanomechanics of multiple units in the erythrocyte membrane skeletal network.

de Oliveira M, Vera C, Valdez P, Sharma Y, Skelton R, Sung LA - Ann Biomed Eng (2010)

Deformation of erythrocytes in microcirculation and the network nanomechanics. (a) Erythrocytes deform (from their biconcave disk shape) extensively in microcirculation where gas exchange occurs in tissue capillaries.30 The flow is from left to right. (b) The dynamics of the membrane skeleton (e.g., the tension in Sp and the attitude of the protofilament) underneath the lipid bilayer may have a pivotal role in transport phenomena, facilitating the movement of some molecules through the lipid bilayer and protein carriers during membrane deformation. The presence of a JC (junctional complex), Sp (spectrin), and SC (suspension complex) in the middle of a Sp tetramer represents two SCs from adjacent units. The pointed end of the protofilament is marked with erythrocyte tropomodulin (E-Tmod, a sphere)
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2914261&req=5

Fig1: Deformation of erythrocytes in microcirculation and the network nanomechanics. (a) Erythrocytes deform (from their biconcave disk shape) extensively in microcirculation where gas exchange occurs in tissue capillaries.30 The flow is from left to right. (b) The dynamics of the membrane skeleton (e.g., the tension in Sp and the attitude of the protofilament) underneath the lipid bilayer may have a pivotal role in transport phenomena, facilitating the movement of some molecules through the lipid bilayer and protein carriers during membrane deformation. The presence of a JC (junctional complex), Sp (spectrin), and SC (suspension complex) in the middle of a Sp tetramer represents two SCs from adjacent units. The pointed end of the protofilament is marked with erythrocyte tropomodulin (E-Tmod, a sphere)
Mentions: Understanding the relationship between the structure of the cell membrane and its mechanical properties will be an important endeavor in cell biology and bioengineering in the next decade.8 An erythrocyte offers the simplest model to study cell membranes as it consists of only a lipid bilayer and an underlying protein skeleton. It is this structure that allows erythrocytes to repeatedly squeeze through small capillaries without compromising their structural integrity (Fig. 1a).FIGURE 1

Bottom Line: While actin protofilaments remain tangent to the network, their yaw (Phi) angles change drastically with addition of neighboring units or an Sp unfolding.It is anticipated that during deformation, transmembrane complexes associated with the network move laterally through the lipid bilayer and increase the diffusion of molecules across the membrane.When protofilament/Sp sweeps under the lipid bilayer, they mix up the submembrane concentration gradient.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, 92093, USA.

ABSTRACT
Erythrocytes undergo deformations when they transport O(2) and CO(2) across the membrane, yet the 3D nanomechanics of the skeletal network remains poorly understood. Expanding from our previous single isolated unit, we now simulate networks consisting of 1-10 concentric rings of repeating units in equibiaxial deformation. The networks are organized with (1) a 3D model for a single unit, (2) a wrap-around mode between Sp and actin protofilament in the intra-unit interaction, and (3) a random inter-unit connectivity. These assumptions permit efficient five-degrees-of-freedom (5DOF) simulations when up to 30 pN of radial forces are applied to the boundary spectrin (Sp) and the center and other units are analyzed. As 6 Sp balance their tensions, hexagonal units become irregular. While actin protofilaments remain tangent to the network, their yaw (Phi) angles change drastically with addition of neighboring units or an Sp unfolding. It is anticipated that during deformation, transmembrane complexes associated with the network move laterally through the lipid bilayer and increase the diffusion of molecules across the membrane. When protofilament/Sp sweeps under the lipid bilayer, they mix up the submembrane concentration gradient. Thus, the nanomechanics of actin protofilaments and Sp may enhance the transport of molecules during erythrocyte deformation.

Show MeSH
Related in: MedlinePlus