Angular scattering analysis of the circular dichroism of biological cells. 1. The red blood cell membrane

Abstract

A quantitative interpretation of the distorted circular dichroism (CD) spectrum of red blood cell membranes [human] was presented including the effects of the intense small angle scattering and light detection geometry and spectrophotometers used. Corrected spectra were obtained by nondestructive methods which corresponded to an in situ membrane protein conformation of 45% .alpha. helix, 10% .beta. sheet and a conformational precision of better than .+-.10%. Forward scattering calculations which neglected the small angle scattering collected by conventional phototube acceptance angles were unsuitable for red cell membranes. UV refractive index dispersion was estimated for the membranes together with an evaluation of the sensitivity of the calculated spectrum to this variable. Angular scattering and CD calculations were extended to 2 alternative models for the location of Hb in pink ghosts; this approach might help in resolving the question whether residual Hb is in solution inside the ghost, or is part of its membrane.