The role of amphiphiles

This paper reviews our work on the partitioning of amphiphilic compounds from the cytoplasm into membranes during drying of plant systems, and discusses how relevant this phenomenon might be for anhydrobiosis. Amphiphilic guest molecules do partition into membranes and oil bodies, as demonstrated by the results of in vivo electron paramagnetic resonance spectroscopy on incorporated spin probes. Arguments for the likelihood of endogenous cytoplasmic amphiphiles behaving similarly during dehydration and rehydration of plant systems are presented. Negative and positive aspects of the partitioning are summarized. Positive aspects are the automatic insertion of amphiphilic antioxidants into membranes of the dehydrating organism, and the control of membrane fluidity and the phase transition temperature. A negative aspect is the perturbation of membrane structure, leading to increased permeability and loss of function. The finding that after an initial fluidization during dehydration, the membrane surface becomes immobilized in desiccation-tolerant systems and not in desiccation-sensitive systems, is discussed in the light of a strict control of the effect of partitioning. The adaptive significance of amphiphile partitioning into the membranes of anhydrobiotes is discussed.