Thylakoid Composition Facilitates Chlorophyll a Dimerization through Stronger Interlipid Interactions.

Plant thylakoid membrane serves as a crucial matrix for the aggregation of chlororophyll a (CLA) pigments, essential for light harvesting. To understand the role of lipid compositions in the stability of CLA aggregates, dimerization of chlorophyll a molecules (CLA) is studied in the presence of the thylakoid and the bilayers comprising either the least or the highest unsaturated lipids by using coarse-grained molecular dynamics simulations. The thylakoid membrane enhances the stability of the CLA dimer compared with other membranes due to very strong lipid-lipid interactions. The thylakoid exhibits a distinct distribution of lipids around the CLA dimer. Less unsaturated lipids reside in close proximity to the dimer, promoting increased order and efficient packing. Conversely, higher unsaturated lipids are depleted from the dimer, imparting flexibility to the membrane. The combination of tight packing near the dimer and membrane flexibility away from the dimer enhances the stability of the dimer in the thylakoid membrane. Our results suggest that lipid mixing, rather than lipid unsaturation, plays a critical role in facilitating CLA dimerization by modulating the membrane microenvironment through stronger lipid-lipid interactions. These insights will be useful in understanding how lipid compositions affect efficient light absorption and energy transfer during photosynthesis in the future.