Absorption and scattering of light by suspensions of cells and subcellular particles: an analysis in terms of Kramers-Kronig relations.

An analysis of light scattering from suspensions of pigmented cells and particles is undertaken, and a practicable method, requiring only the experimentally measured extinction spectra, is documented. The analysis is based on two premises: Absorption and selective scattering from a single pool of pigments satisfy the Kramers-Kronig relations, which imply that one can be derived from the other; pigment-free domains contribute only nonselective scattering. This approach succeeds in simulating the spectra of many systems (human erythrocytes, chloroplasts and subchloroplast particles, algal cells) over a wide spectral range. Other, less favourable, cases are also examined, but even here the apparent discrepancy between theory adn experiment provides some clues that cannot be gleaned from absorption data alone.