Fig. 3

Structures of protein-ligand complexes that form potentially labile structures. Weak hydrogen bonds (W_QB < 4 kcal mol⁻¹) marked in green. a Complex of FXa with inhibitor RPR208707 (PDB id 1F0S; K_i = 18 nM) forms two direct, but labile, HBs with the protein. An additional water-mediated HB with the catalytic residues (yellow dotted lines) might provide structural stability. b An antibody that recognizes phosphocholine (PDB id 2MCP) forms two charge-reinforced but labile HBs. A cation-pi interaction (yellow dotted lines) might provide structural stability. c Reverse transcriptase inhibitor (PDB id 1JLA; IC₅₀ = 6 nM) forms a single but labile HB with the protein. No other source of structural stability is apparent