Birefringence of protein solutions and biological systems. I.

The quantitative interpretation of birefringence of biological structures such as muscle requires a knowledge of intrinsic birefringence of the components. The intrinsic birefringence of fibrous structures as determined by variation of solvent index is positive while the intrinsic birefringence of proteins in solution is negative as calculated by the Peterlin-Stuart theory. As a first step in clarifying this discrepancy the basis of the Peterlin-Stuart theory has been re-examined. The theory has been recalculated from the standpoint of light scattering and extended to particles whose length is not small compared to the wavelength. The birefringence of a system of particles possessing a shell with index different from the bulk solvent has been obtained in order to interpret measurements in mixed solvents.