Absorption and Circular Dichroism Spectroscopies

The obtaining of absorption and circular dichroism spectra of a suspension of biological membranes is a relatively simple and quick procedure. Extracting correct and meaningful information from these spectra is not so simple and quick. In this chapter an effort will be made stepwise to present the problem of the application to the study of biomembranes of the physical methods of ultraviolet absorption and circular dichroism spectroscopies. This will be approached by first considering solutions, the phenomena that occur and type of information that is available in solution. Next will be considered suspensions of homogeneous particles and how to improve their distorted spectra, and finally the added complication of suspensions of heterogeneous particles (biomembranes) will be noted by presenting data on the three major sources of membrane absorption (lipids, protein side chains, and protein backbone) in several biomembranes and carrying out approximate corrections on experimental ellipticities.