The simulations suggest the following model for the surface effect on dimer formation. Interaction of a monomer with the surface is accompanied by the structural transition of the monomer. Another monomer binds to the immobilized monomer, forms a dimer in which both monomers undergo a structural transition. As a result, the interaction with the surface accelerates the formation of dimers. Compared to our previous simulations for dimer formation by free Aβ(14-23) monomers in which no major structural changes were observed during the first ~200 ns23, we have an almost five-fold faster structural transition when the peptides interact with the surface.