Crystallization-induced changes in protein structure observed by infrared spectroscopy of carbon monoxide liganded to human hemoglobins A and Zurich

The relationship of a protein structure obtained by crystallography to the in vivo solution structure is of great interest in the study of protein structure and function. Upon crystallization the structure of a protein molecule may change due to crystal lattice forces and different hydration levels. With hemeprotein ligand infrared spectra can provide a sensitive probe for monitoring ligand site structures in both crystals and solutions. The spectra for CO, CN super(-), N sub(3) super(-), NO, and O sub(2) as ligands have been observed for several hemeproteins in solution and provide evidence the multiple ligand site structures (conformers) are present.