Ligand–protein recognition studies as determined by nuclear relaxation analysis

The ligand–macromolecule interaction is analysed in terms of selective (R1SE) and non-selective (R1NS) spin–lattice relaxation rates, considering the contribution arising from all possible specific and non-specific receptor sites. A linear relation between ΔR1SE and macromolecule concentration is demonstrated to exist under any coordination conditions. The slope of the straight line obtained is defined as the `affinity indexʹ which is proposed as a general criterion for assessing the total ability of a ligand to interact with a macromolecule.