Distortions in circular dichroism patterns of particulate (or membranous) systems

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Abstract

Two sources are proposed for the distortion of circular dichroism patterns of particulate systems. One is the absorption flattening of Duysens and the second, for which equations are derived, is a dispersion distortion due to light scattering. Both result in wavelength-dependent decreases in the number of absorbing units. As such the Kronig-Kramers transforms which relate circular dichroism and optical rotatory dispersion are valid and shifts and decreases in magnitude observed with one physical measurement will be reflected in the other.

The Duysens absorption flattening results in maximum damping at the wavelength of the absorption peak. The dispersion distortion results in maximum damping at positions defined by the half-width of the absorption band in accord with anomalous dispersion in absorption regions. In terms of polypeptide circular dichroism this results in greatest damping of ellipticity near 208 mμ.

When these wavelength-dependent effects are applied to the circular dichroism pattern of helical poly-γ-methyl-l-glutamate the circular dichroism curve characteristic of membranes is obtained. Thus the red shift and decreased magnitude of membrane CD curves are in part the result of the particulate nature of a system wherein about half of the polypeptide exhibits the features of an α-helix.

References (17)

  • B. Ke

    Arch. Biochem. Biophys

    (1965)
  • B. Ke
  • D.W. Urry et al.
  • D.F.H. Wallach et al.
  • J. Lenard et al.
  • D.W. Urry et al.
  • J.M. Steim et al.
  • J. Lenakd et al.

    Science

    (1968)
There are more references available in the full text version of this article.

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1

Post Doctoral Fellow supported by the Education and Research Foundation of the American Medical Association.

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