Kotakis C. author Akhtar P. author Zsiros O. author Garab G. author Lambrev P. H. author text journal article 2018 The principal function of the thylakoid membrane depends on the integrity of the lipid bilayer, yet almost half of the thylakoid lipids are of non-bilayer-forming type, whose exact functions are not fully understood. Non-bilayer lipids can be extruded from the membrane in the presence of high concentrations of co-solutes. We applied 2 M sucrose to induce lipid phase separation in isolated thylakoid membranes, following consequent structural and physiological effects. Circular dichroism spectroscopy indicated significant changes in the chiral macro-arrangement of the pigment-protein complexes, which were reversed after washing out the co-solute. Similarly, merocyanine-540 fluorescence suggested reversible changes in the lipid phases. The PSII function, as tested by chlorophyll fluorescence induction transients and time-resolved fluorescence, was almost unaffected. However, the presence of sucrose dramatically increased the PSII thermostability, which can partly be explained by a direct osmolyte effect and partly by the lipid phase separation stabilizing the stacked membrane. circular dichroism; merocyanine-540; non-bilayer lipids; osmolyte; time-resolved fluorescence spectroscopy 10.1007/s11099-018-0782-z https://ps.ueb.cas.cz/artkey/phs-201801-0024.php https://ps.ueb.cas.cz/artkey/phs-201801-0024.php continuing 56 1 254 264 2018 03003604 periodical academic journal