Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Transmembrane glycoproteins, glycophorin and the Concanavalin A receptor, were assembled into large multilamellar liposomes. Lectin binding to these simple model membranes was positive-cooperative. The high affinity lectin binding to liposomes was influenced by the presence of unrelated macromolecules (serum albumin and Dextran T-500) at the membrane surface. Since under appropriate conditions the model membrane system appeared to accurately mimic the positive-cooperative behavior observed for binding of various lectins to intact cells, it is suggested that the source of the high affinity binding and its positive-cooperative nature in the described system is the lectin-induced, surface coat dependent 'chelate' or 'avidity' effect. This effect was more important than lipid fluidity, temperature, and gross receptor distribution.;The time dependence of wheat germ agglutinin and Concanavalin A binding to two integral membrane glycoproteins has been examined in lipid bilayers. The curves have been compared to those for the same receptor in intact cells. Freeze-etch electron microscopy and fluorescence microscopy were used to examine receptor distribution. It is suggested that the glycoprotein headgroup is a deformable structure whose lectin-mediated rearrangement over short distances is essential for high affinity binding and is responsibile for the time-dependent binding curves observed.;Gangliosides, spin labelled on N-acetylneuraminic acid residues or on random-headgroup sugars, have been used to study their physical behavior in three lines of cultured cells. Headgroup sugar mobility was seen to be homogeneous. The spin labelled gangliosides incorporated into intact cells showed clear spectral immobilization features similar to those observed with model membranes probably reflecting the interaction of the ganglioside headgroup with the glycocalyx of intact cells.



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