Energy transfer and its dependence on membrane properties.

With isolated chloroplasts variations in the degree of energy transfer between light-harvesting chlorophyll-protein complexes can be induced by changing the cation content of the suspending medium. The changes can be observed by measuring chlorophyll-fluorescence yields and lifetimes and are probably brought about by conformatial changes in the thylakoid membrane. Detailed studies of the properties of cation-induced changes in chlorophyll fluorescence indicated that the alterations in pigment organization are due to variations in the density of positive charges immediately adjacent to the surface of the thylakoid membrane, being in qualitative agreement with predictions based on the Gouy-Chapman theory of diffuse double layers. Possible mechanisms for the membrane structural changes controlling energy transfer are given.