[13] Stationary and time-resolved circular dichroism of hemoglobins

This chapter reviews the applications of circular dichroism (CD) spectroscopy to hemoglobin (Hb). This chapter discusses essentials of CD theory. Because many electronic states are involved in proteins, it is possible to investigate the molecule in different wavelength regions. Each region contains some information concerning a part of the three-dimensional (3D) organization of the macromolecule. By choosing a set of different wavelengths, different chromophores can be observed. In the spectral region below 250 nm, the optical activity is dominated by the peptide backbone organization. Protein structural analysis is interpreted by the existence of a correlation between CD spectra and the organization of the secondary structure: α helix, β sheet, and random coil. The CD spectrum of each secondary structure is assumed to be independent of others, and the resulting CD spectrum is a simple summation. In the chapter, two kinds of reference were used to analyze protein structure by CD.