Deuterium-exchange profiles for individual peptides show significant differences in local structural order in variable loop truncation variants. (A) Mapping of selected peptides showing differences in deuterium exchange between FL and other proteins (ΔV3, ΔV1/V2, Coree, and FL+sCD4) on the structure of the gp120 monomer (PDB entry 4NCO). (B–J) Individual deuterium uptake profiles for different peptides from layer 1 (B), layer 2 (C), and layer 3 (H and I) of the inner domain; the bridging sheets (D, F, and G); the CD4-binding loop (E); and the V2 loop (J). HXB2 numbering is applied for the primary sequence.