17] Circular dichroism analysis of nucleoprotein complexes

Abstract

This chapter discusses the analysis of nucleoprotein optical activity spectra. Although most spectroscopic methods—for example, infrared, nuclear magnetic resonance, and fluorescence—are particularly sensitive to the atomic composition of chemical groups and only grossly affected by the geometric arrangement of these groups or the geometry of their environment, optical activity spectroscopy is uniquely sensitive to these geometric aspects of molecular structure. One of the most biologically significant and interesting complexes is the eukaryote chromosome. In conjunction with genetic activity studies and chemical studies of this structure, much interest has been demonstrated recently in the studies of the geometry or conformation of chromatin and simpler nucleoprotein complexes. Although optical activity spectroscopy began with optical rotatory dispersion measurements, this spectral method has been largely replaced by the more sensitive and reliable method of circular dichroism. An understanding of circular dichroism spectroscopy requires both the knowledge of the polarized energy used and the nature of its interaction with matter.