Figure 2. Investigating heme binding to peptides or proteins by various spectroscopic methods.

Complex formation can be detected by UV/Vis spectroscopy, in particular by a shift of the heme-characteristic Soret-band. Upon binding the heme-iron coordination state, i.e. the occurrence of a penta- and/or hexa-coordinated complex, can be investigated by rRaman and cwEPR spectroscopy, focusing amongst others on the ν₃ band (rRaman) and the signals around g ∼ 6 and g ∼ 2 (cwEPR). The topology and structure of the formed complexes can be clarified by applying 2D- or 3D-NMR spectroscopy [32,33].