The spectral dependence of scattering from a spherical alga and its implications for the state of organization of the light-accepting pigments.

Abstract The cause of the spectral displacement of the 660-mμ band of extracted chlorophyll in organic solvents to about 680 mμ in vivo , as measured directly in algae suspensions, is of importance with respect to the role which energy transfer between the chlorophyll molecules plays in photosynthesis. The enhanced scattering on the long wavelength side of an absorption band in large particles, originally discussed by Price and Tetlow and invoked by Latimer and Rabinowitch to help explain this bathochromic shift, has been experimentally examined. A semiempirical theory has been developed which satisfactorily characterizes the effect. It is demonstrated that only a small part of the spectral shift arises from this selective scattering; the in vivo absorption band is established to occur at 674–675 mμ, some 10–15 mμ further to the red than the extracted pigments, indicating that a change in the environment of the chlorophyll molecules is responsible for the shift.