Conformation and elasticity of the isolated red blood cell membrane skeleton

Svoboda, K., Schmidt, C. F., Branton, D., Block, S. M. (September 1992) Conformation and elasticity of the isolated red blood cell membrane skeleton. Biophys J, 63 (3). pp. 784-93. ISSN 0006-3495 (Print)0006-3495 (Linking)

URL: http://www.ncbi.nlm.nih.gov/pubmed/1420914
DOI: 10.1016/S0006-3495(92)81644-2

Abstract

We studied the structure and elasticity of membrane skeletons from human red blood cells (RBCs) during and after extraction of RBC ghosts with nonionic detergent. Optical tweezers were used to suspend individual cells inside a flow chamber, away from all surfaces; this procedure allowed complete exchange of medium while the low-contrast protein network of the skeleton was observed by high resolution, video-enhanced differential interference-contrast (DIC) microscopy. Immediately following extraction in a 5 mM salt buffer, skeletons assumed expanded, nearly spherical shapes that were uncorrelated with the shapes of their parent RBCs. Judging by the extent of thermal undulations and by their deformability in small flow fields, the bending rigidity of skeletons was markedly lower than that of either RBCs or ghosts. No further changes were apparent in skeletons maintained in this buffer for up to 40 min at low temperatures (T less than 10 degrees C), but skeletons shrank when the ionic strength of the buffer was increased. When the salt concentration was raised to 1.5 M, shrinkage remained reversible for approximately 1 min but thereafter became irreversible. When maintained in 1.5 M salt buffer for longer periods, skeletons continued to shrink, lost flexibility, and assumed irregular shapes: this rigidification was irreversible. At this stage, skeletons closely resembled those isolated in standard bulk preparations. We propose that the transformation to the rigid, irreversibly shrunken state is a consequence of spectrin dimer-dimer reconnections and that these structural rearrangements are thermally activated. We also measured the salt-dependent size of fresh and bulk extracted skeletons. Our measurements suggest that, in situ, the spectrin tethers are flexible, with a persistence length of approximately 10 nm at 150 mM salt.

Item Type: Paper
Uncontrolled Keywords: Elasticity Erythrocyte Membrane/*ultrastructure Humans Male Microscopy, Interference/instrumentation/methods Osmolar Concentration Video Recording/instrumentation/methods
Subjects: physics > biophysics > membrane dynamics
organs, tissues, organelles, cell types and functions > tissues types and functions > membranes
organs, tissues, organelles, cell types and functions > cell types and functions > cell types > red blood cells
organs, tissues, organelles, cell types and functions > cell types and functions > cell types > red blood cells
organs, tissues, organelles, cell types and functions > cell types and functions > cell types > red blood cells
CSHL Authors:
Communities: CSHL labs > Svoboda lab
Depositing User: Matt Covey
Date: September 1992
Date Deposited: 01 Oct 2015 19:13
Last Modified: 01 Oct 2015 19:13
PMCID: PMC1262211
Related URLs:
URI: http://repository.cshl.edu/id/eprint/31775

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