Figure 1.

Ligands targeting charged areas on protein surfaces discussed in this review. The protein shown as example is hPin1 (pdb 1NMV, [75]). The guanidiniocarbonylpyrrole motif (GCP, top left) recognizes the carboxylate groups of aspartate or glutamate residues by forming an extended H-bonding network [41–46]. Supramolecular tweezers (top center) thread lysine or arginine side chains into their aromatic cavities [5–18]. Calixarenes (top right, [19–40]), Ru^II(bpy)₃ complexes (bottom left, [61–63]) and porphyrins (bottom center, [52–60]) can be functionalized with either multiple acidic or basic groups to target charged areas of either polarity on a protein surface. Cucurbiturils (bottom right, [47–51]) recognize methylated lysines and arginines by binding their methylated head groups inside the macrocycle.