A two-dimensional many-body system with competing interactions as a model for segregation of photosystems in thylakoids of green plants.

We address the segregation of photosystems I (PSI) and II (PSII) in thylakoid membranes by means of a molecular dynamics method. We assume a two-dimensional (in-plane) problem with PSI and PSII being represented by particles with different values of negative charge. The pair interactions between particles include a screened Coulomb repulsive part and am exponentially decaying attractive part. Our modeling results suggest that the system may have a complicated phase behavior, including a quasi-crystalline phase at low ionic screening, a disordered phase and, in addition, a possible "clotting" agglomerate phase at high screening where the photosystems tend to clot together. The relevance of the observed phenomena to the stacking of thylakoid membranes is discussed.