Circular Dichroism Studies of Electron-Transport Components

Abstract

Publisher Summary Optical activity spectroscopy is a recognized tool for the examination of the conformation of biological macromolecules. This chapter discusses Ootical rotary dispersion (ORD) and circular dichroism (CD). They are two interrelated modes of the optical activity spectrum. ORD is the wavelength dependence of the ability of a chromophore to rotate a plane of linearly polarized light. The spectrum from a single transition is composed of a positive and a negative component, and has finite optical activity throughout the entire spectrum except at the wavelength of the transition. CD, on the other hand, is the wavelength dependence of the difference in the ability of the chromophore to absorb right- and left-handed circularly polarized light. The nature of the spectrum is that of an absoption band in solution, but the band could be either positive or negative. This absorption-dispersion profile of the optical activity spectrum is called a Cotton effect. ORD and CD profiles are interconvertible by a well-established mathematical transformation. CD spectroscopy has been the more prevalently used mode of optical activity spectroscopy because of the simplification of the spectrum resulting from its property of vanishing in all other areas of the spectrum except within the region of an optically active absorption band