HIV viral protein interactions with cellular receptors are vital to the infection process. It is in this context that the HIV GP120 viral envelope protein interactions with lipid bilayers and CD4 receptors have been studied. It was demonstrated that the GP120 protein “sinks” into the lipid bilayer over time, a significant ability when considering its biological role. GP120 can also assemble into larger structures on lipid bilayers and forms unusual micron scale aggregates when preformed complexes are deposited on mica. It is possible to distinguish individual GP120/CD4 complexes when the receptor is reconstituted into the lipid bilayer with the force required to unfold the complex greater than the force required to unfold either of the individual components.