New Cellular Biomechanics Technique

Sowers, Arthur

Abstract

A recent paper from our laboratory (Chernomordik and Sowers, 1991) suggested the idea that a new cell biomechanics technique might he developed based on the use of electrically-fused doublet membranes. This idea is based on the time-dependent increases in the diameter of a fusion zone which is induced in the contact area shared by two erythrocyte ghosts. Data now submitted show that these diameter vs. time curves have an extraordinary amount of kinetic detail which we have now traced to the spectrin network. Subsequent data (also now submitted) showed that detectable microforces can, indeed be applied to these membranes through dielectrophoresis, an obscure biophysical effect which has the desirable properties of being mild, completely reversible, and non chemical. A second idea, now backed by new preliminary data, was to use osmotic pressure differences from solutes present in the cytoplasmic and external compartments to generate a separate set of microforces to probe the mechanical and structural properties of the spectrin based membrane- skeleton.
Our Specific Aims are to: #1 Determine if the force causing expansion of the two sphere doublet into a single large sphere can he augmented or inhibited by an osmotically based counter force generated by having a solute present in the cytoplasmic compartment or in the extracellular compartment. We will also develop a model for this interaction. #2 Calibrate the force generated by dielectrophoresis. #3 identify any possible limiting factors and conditions, and #4 analyze and manage any anticipated artifacts. Erythrocyte ghosts will be fused and observed by computer-assisted video analysis in both fluorescence and phase optics modes. As a forerunner to a more extended study, it is foreseen that development of this fused-doublet technique may permit structure-function relationships in membrane based lipid-protein assemblies to be probed in a new way. In fact, ongoing studies to qualitatively elucidate the basis for the kinetic detail (see Figs 2 and 3) strongly implicate the spectrin-based membrane skeleton. Appropriate use of biochemical and chemical conditions, immunological, genetic manipulation (by molecular biology or species of origin), or use of samples from individuals with specific diseases are likely to help understand how these supra-molecular assemblies function.