Three sequences of simple protein models on the two-dimensional square lattice have been chosen for a study of the behavior of different classes of proteins as a function of temperature and concentration using multimolecular systems under periodic boundary conditions. The results of the dynamic simulations have shown the profound influence that the intermolecular contacts can have on the accessibility of the states the various sequences can reach: this makes possible the formation of different kinds of structures under the control not only of sequence and temperature but also of concentration that can become the main driving force for the formation of ordered lamellar structures for sequences properly designed.