Professor Nichol is known and respected internationally as a leader in the development, application and interpretation of except physicochemical methods, particularly those of sedimentation equilibrium and mass migration, for characterizing thermodynamic and kinetic aspects of interactions of biological macromolecules, important for understanding the stability of cellular systems and the control of metabolic processes. He has especially contributed to knowledge of: (i) the occurrence and kinetic significance of sigmoidal ligand-binding curves, (ii) the separate assessment of molecular aggregation and thermodynamic non-ideality, (iii) the occurrence of indefinite self-associations, (iv) the measurement of associations by simple mass­migration methods. His contributions have become widely known through his generous collaboration with others.