Giant circular dichroism of high molecular weight chlorophyllide-apomyoglobin complexes

Abstract
Chlorophyllide a and the apoprotein of myoglobin (Mb) spontaneously form 3 types of complex. The M (MW .apprxeq. 3 .times. 105) and H (MW .gtoreq. 4 .times. 106) complexes, but not the L (MW .apprxeq. 1.7 .times. 104), display a circular dichroism (CD) spectrum that is highly red-shifted, nonconservative, and very intense, characteristics shared by the CD spectra of reaction center complexes from purple photosynthetic bacteria. At its 710-nm peak, the H complex CD spectrum has a larger magnitude, 0.06 differential absorbance per unit total absorbance, than has been reported for chlorophyll in any medium.