MOLECULAR MAPS OF RED-CELL DEFORMATION - HIDDEN ELASTICITY AND IN-SITU CONNECTIVITY

Fluorescence-imaged micropipette aspiration was used to map redistribu tion of the proteins and lipids in highly extended human red blood cel l membranes. Whereas the fluid bilayer distributed uniformly (+/-10 pe rcent), the underlying, solidlike cytoskeleton of spectrin, actin, and protein 4.1 exhibited a steep gradient in density along the aspirated projection, which was reversible on release from deformation. Quantit ation of the cytoskeletal protein density gradients showed that skelet al elasticity is well represented by a grafted polymer network with a ratio of surface dilation modulus to shear modulus of approximately 2: 1. Fractionally mobile integral proteins, such as band 3, and highly m obile receptors, such as CD59 as well as glycophorin C in protein 4.1- deficient cells, appeared to be squeezed out of areas dense in the und erlying network and enriched in areas of network dilation. This comple mentary segregation demonstrates patterning of cell surface components by cytoskeletal dilation.