Metastable equilibrium with random local fluctuations: simulations of dynamic receptor pattern generation in a fluid mosaic membrane.

The generation of receptors in the animal cell's membrane was simulated by a model consisting of units in four possible states within a hexagonal area (playboard) of n units of a triangular network. The state of each unit was determined by the previous state of itself and of its six nearest neighbours, as regulated by a set of transition rules, which kept the mean relative frequency (m.r.f.) of each state constant. The transition rules were applied to the system exactly n times, regardless whether this involved selection of a unit on 0, 1, 2 or more occasions (programme "random selection with repeat"; RS-R). Comparison to previous results obtained by other ways of application of the rules has shown that the RS-R programme accounted for the highest m.r.f. of quiet (Q) units and Q clusters (sub-patterns), and also for the longest survival of Q configurations through several generations. Functioning of the model under the RS-R programme simulates an integrated system in metastable equilibrium with random local fluctuations, such as the cytoplasmic membrane is imagined to be in standardized environmental conditions. The formation-persistence-disintegration cycle of the sub-patterns is believed to simulate the dynamic generation of transitory receptor configurations in the cell membrane.