Heme molecular structure, comparison

The recently solved X-ray structures of rabbit microsomal CYP2C5 in complex with diclofenac [190] and a sulfaphanazole derivative [191] provided additional evidence on how the molecular recognition of structurally diverse substrates takes place. Comparisons of the complex with apo CYP2C5 [119] indicates that the protein closes around the substrate and prevents open access of water from bulk solvent to heme Fe. Multiple substrate binding models of the sulfaphenazole derivative are in agreement... 

Because MCD signals can be either positive or negative in sign, considerably more fine structure is seen in MCD spectra than in the corresponding electronic absorption spectra. Furthermore, MCD is a property of the molecular electronic structure of a chromophore, and so the only structural changes that will influence the MCD spectrum are those that modify the electronic structure. Furthermore, the MCD spectrum is relatively insensitive to the environment in which the chromophore is located, whether it is the protein microenvironment for a heme protein center or the solvent for a model complex. Thus, comparisons of the MCD spectra of synthetic heme iron model complexes with those of heme protein active sites are possible and have been shown to be of considerable utility in assigning the coordination structures of the heme protein active sites (I). 

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