FTIR and calorimetric investigation of the effects of trehalose and multivalent cations on lipid structure

The structure of membrane lipids is of fundamental importance for the integrity of cell and organelle membranes in living organisms. Membrane lipids are typically hydrated and their headgroup charges counter-balanced by solvated ions. Consequently, water loss can induce severe structural changes in lipid packing (lyotropic transitions) and can lead to the damage of lipid membranes even after rehydration. This can be one out of several factors that affect the viability of organisms undergoing desiccation. Many organisms, however, are resistant to even extreme water loss. Some of them synthesize trehalose which has been shown to be associated with survival of desiccation in phylogenetically diverse organisms (yeast, nematodes, brine shrimp, insect larvae, resurrection plants, and others). Here we have studied hydration sensitive transitions in model lipids to determine the effect of trehalose and electrostatics on lipid order. Hydration pulse-induced time-resolved Fourier-transform infrared (FTIR) difference spectroscopy was used to address hydration-dependent lipid structure as a function of trehalose. In combination with differential scanning calorimetry and studies of Langmuir-Blodget films we arrive at a structural and energetically consistent picture of how trehalose can affects lipidic phase behaviour and support a native lipid structure under water loss. Experiments were performed on model lipids with different headgroups and native lipids from desiccation-tolerant organisms.