5] Optical measurements of quaternary structural changes in hemoglobin

Abstract

This chapter focuses on the optical measurement of quaternary structure changes in hemoglobin (Hb). Ligand-linked quaternary structural changes have been documented either indirectly, by modeling of the equilibrium and kinetics of ligand binding and the ligand-linked tetramer-dimer dissociation, or directly, mainly by X-ray crystallography and spectroscopy. Spectroscopic techniques that have been extensively employed to probe the quaternary conformational changes in Hb are nuclear magnetic resonance (NMR) and resonance Raman. This chapter discusses namely the use of static and dynamic optical spectroscopy in the characterization of the quaternary structural changes in Hb. This chapter discusses optical changes of the heme and of the globin associated either with the assembly process involved in the formation of tetrameric Hb or with the ligand-linked quaternary change of the tetramer. This may be taken as evidence that the dynamic pathway of the quaternary change in fully deoxygenated Hb is rate limited by a single barrier that controls the interface structural transition and the heme perturbation.