Square lattice protein models are used to study the competition
between folding and aggregation phenomena. The problem is
approached by considering Metropolis Monte Carlo simulations of
non-isolated lattice protein models; different protein molecules
can interact each other and, in competition with folding, can
aggregate by forming dimers. The calculations take in exam the
behavior of three types of proteins: a) proteins with a very
well designed sequence (good folders); b) proteins which folding
kinetics present kinetic partitioning effects (intermediate
folders); c) small proteins with native states having the
geometry of pure secondary structure motives (like alpha helices
or beta sheets). The results show that good folders very rarely
form aggregates; on the contrary, in almost all considered cases,
intermediate folders display high tendency to form dimers.
Finally, alpha helices display a low tendency to aggregate in
comparison to that found for beta-sheets. However, also for these
systems, structural intermediates in the folding kinetics can
strongly influence the aggregation tendency.
