Stabilization of gp120 monomers caused by deletions of variable loops as detected by H/D exchange. (A) Deuterium exchange for FL, ΔV3, ΔV1/V2, Coree, and FL+sCD4 at 1 min plotted on the heat map (from left to right). (B) Differences in deuterium exchange between FL and ΔV3, FL and ΔV1/V2, FL and Coree, and FL and FL+sCD4 at 1 min plotted on the heat map. The degrees of change between the two proteins are colored from white (<20% difference) to orange (20–50% difference) to red (>50% difference).