The free energy change of restricting a bond rotation in the binding of peptide analogues to vancomycin group antibiotics

The adverse cost in free energy of restricting an internal bond rotation in the binding of the peptide ligands N-succinyl-D-alanine and N-fumaryl-D-alanine to the antibiotic Ristocetin A, has been estimated to be 3.7 ± 0.9 kJ mol per rotor by comparison of the difference in free energies of binding measured by UV spectrometry.