Angular scattering analysis of the circular dichroism of biological cells. 2. The red blood cell.

A detailed interpretation of the grossly distorted ultraviolet absorption and circular dichroism spectra of the intact red blood cell is given, including an evaluation of the effects of protein conformation, detector geometry, cell hemoglobin content, and refractive index on the calculated cell spectra. The origins of the major differences between cell and hemoglobin solution spectra were quantitatively accounted for in terms of differential scatter and absorption flattening, with the latter effect dominating the picture. The relatively low sensitivity of the red blood cell suspension circular dichroism spectrum to hemoglobin conformation is due to the order of magnitude flattening of circular dichroism intensity. The importance of accounting for instrumental light detection geometry and the intense small angle scattering (less than 8 degrees) for a range of particle sizes (0.1-5 mum) is made clear.