Induced Circular Dichroism of Heme and Chlorophyll Bound to Proteins

6 Induced Circular Dichroism of Heme and Chlorophyll Bound to Proteins 

On the other hand, the simple complexes (hemins I and II) have a reverse relation between the ICD magnitudes in the Soret region and the ligand field strengths of the axial ligands bound to the heme for peptides and proteins. This difference between our models 199) and Urry s findings 196 198 may be partly due to the existence of the ring(s) with optically active center(s). 

An alternative example has been reported by Boxer et al. 201 202 They formed well-defined complexes of chlorophyll and bacteriochlorophyllide with apomyo-globin. The chlorophyllide and its derivatives substitute for heme in the hydrophobic 

Dotted line 3-(l-imidazolyl)propyIaminated pyrochlorophyllide a Mg(II)-apomyoglobm complex, 10 5 M in CH2C12 

The CD features of bacteriochlorophyll a in light-harvesting bacteriochlorophy 11-protein complexes from native bacteria is more interesting and is not compatible with Boxer s experiments. Bacteriochlorophyll(Bchl)-protein complexes exhibit various CD spectral profiles, depending on the species of bacteria and their culture conditions 201 206). Thus, CD of Bchl arises from the asymmetric environment in which the Bchl is situated, and from the specialized arrangement which affords a specific interaction between Bchl molecules, as well as from the asymmetry of Bchl 

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