Figure 3

Distribution of strain energies and α-carbon distances for the -LHStaple disulfides in NMR and X-ray structures. A major fraction of the 1,805 -LHStaple bonds in NMR structures (part A) have a high strain energy (~50 kJ.mol^-1) and short α-carbon distance (~4 Å). The majority of the 599 -LHStaple bonds in X-ray structures (part B) have a low strain energy (~10 kJ.mol^-1) and long α-carbon distance (~6.5 Å). Example of a short, high energy -LHStaple (the Cys45–Cys56 bond in fibronectin, PDB ID 1o9a) and a long, low energy -LHStaple (the Cys133–Cys193 bond in urokinase plasminogen activator, PDB ID 2fd6) is shown in part C. The fibronectin disulfide is a NMR structure (Table 4), while the urokinase plasminogen activator disulfide is a X-ray structure with a resolution of 1.9 Å, a DSE of 2.9 kJ.mol^-1 and an α-carbon distance of 6.5 Å. The structures look at the side of the S-S bond, which is shown in the horizontal position. They were generated using PyMol [35].