Transverse and Lateral Heterogeneity in Membrane Fluidity in Thylakoids, Galactolipid Vesicles, and an Oxygen evolving Photosystem II Preparation

Abstract

There has recently been considerable interest in the lateral heterogeneity of the thylakoid membrane (1,2). This lateral separation of photosystems I and II requires some form of relatively long distance electron transport between the two photosystems. Anderson (1,) has proposed that plastoquinone could act as the electron shuttle between the two isolated photosystems. It is now thought by some, that PQ resides between the two galactolipid leaflets, where overall membrane fluidity is maximal. To test this model we have probed the membrane fluidity with a variety of spin labels in hope of documenting the increased fluidity at the membrane interior. We also hoped to examine the influence of intrinsic proteins on lipid order and immobilization.