The circular dichroism and optical rotatory dispersion patterns of biological membranes resemble, in gross aspect, those of the α-helix but the extrema are red shifted and of low amplitude. Such patterns are not typical for solublized membrane lipoproteins but rather are exhibited by the aggregates of membrane proteins (Steim and Fleishcher, 1968), as well as by aggregated polypeptides and antibiotics (Urry and Ji, 1968 b). Since particulate systems exhibit flattened absorption bands (Duysens, 1956) and light scattering, it is of interest to experimentally relate changes in the circular dichroism patterns with these effects. Absorption flattening results in a decrease of absorbance due to a decrease in the effective concentration of absorbers, while light scattering results in a light intensity loss and thereby an increase in absorbance as measured by the phototube. Light scattering also results in a concentration obscuring effect. The extent of light scattering and absorption flattening can differ slightly for the left-handed and right-handed circularly polarized light. Thus these effects could accentuate distortions in the ORD and CD patterns of particulate systems as compared to the molecularly dispersed samples. Previously it has been demonstrated that the low amplitude of the membrane type CD curve can be generated from the characteristic α-helix CD pattern by applying correction factors for light scattering and absorption flattening (Urry and Ji, 1968 a & b). In this communication it is shown that the red shift and decrease in amplitude of the CD extrema of particulate systems correlate with changes in the intensity of scattered light and with the extent of absorption flattening as measured, respectively, at wavelengths where significant absorption does not occur and at wavelengths corresponding to major absorption bands. © 1969.
