An NMR spectroscopy study of bendaline–albumin interactions

The complete assignment of the 1H and 13C NMR spectra of bendaline (BNDL) was performed by mono-dimensional and homo- and hetero-correlated two-dimensional NMR experiments. The interaction between bendaline and albumin was also studied by the analysis of the motional parameters spin–lattice relaxation times, allowing the motional state of the BNDL free and bound with albumin to be defined. In absence of albumin the indazolacetic and benzylic moieties are characterized by roughly the same mobility and by positive σ (cross-relaxation rates) values. In the presence of the macromolecule, the indazolacetic and benzylic moieties and the lysine change their motional behaviour to different extents, as indicated by correlation times. Data obtained in absence and in presence of the protein show that the molecular moiety of the bendaline most involved in the binding with albumin is the fragment H-4 H-5. The binding constant was evaluated at 2.4 × 103 M−1.