Kinematics of red cell aspiration by fluorescence-imaged microdeformation.
Maps of fluorescing red cell membrane components on a pipette-aspirated projection are quantitated in an effort to elucidate and unify the heterogeneous kinematics of deformation. Transient gradients of diffusing fluorescent lipid first demonstrate the fluidity of an otherwise uniform-density bilayer and corroborate a "universal" calibration scale for relative surface density. A steep but smooth and stable gradient in the densities of the skeleton components spectrin, actin, and protein 4.1 is used to estimate large elastic strains along the aspirated skeleton. The deformation fields are argued to be an unhindered response to loading in the surface normal direction. Density maps intermediate to those of the compressible skeleton and fluid bilayer are exhibited by particular transmembrane proteins (e.g., Band 3) and yield estimates for the skeleton-connected fractions. Such connected proteins appear to occupy a significant proportion of the undeformed membrane surface and can lead to steric exclusion of unconnected integral membrane proteins from regions of network condensation. Consistent with membrane repatterning kinematics in reversible deformation, final vesiculation of the projection tip produces a cell fragment concentrated in freely diffusing proteins but depleted of skeleton.
Discher
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DE
Department of Physics, Simon Fraser University, Burnaby, BC, Canada. discher@eniac.seas.upenn.edu
Mohandas
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N
D000199:Actins / Q000097:blood; D001457:Anion Exchange Protein 1, Erythrocyte / Q000032:analysis; D001798:Blood Proteins / Q000032:analysis*; D018957:CD59 Antigens / Q000097:blood; D004907:Erythrocyte Deformability; D004910:Erythrocyte Membrane / Q000502:physiology / Q000648:ultrastructure*; D006021:Glycophorins / Q000032:analysis; D006801:Humans; D008051:Lipid Bilayers; D008563:Membrane Lipids / Q000097:blood; D008565:Membrane Proteins / Q000097:blood; D008961:Models, Structural; D008962:Models, Theoretical; D010743:Phospholipids / Q000097:blood; D013049:Spectrin / Q000032:analysis; D013050:Spectrometry, Fluorescence / Q000379:methods
D000199:Actins; D001457:Anion Exchange Protein 1, Erythrocyte; D001798:Blood Proteins; D018957:CD59 Antigens; D006021:Glycophorins; D008051:Lipid Bilayers; D008563:Membrane Lipids; D008565:Membrane Proteins; D010743:Phospholipids; D013049:Spectrin