Recent epidemiological data have shown that patients suffering from Type 2 Diabetes Mellitus have an increased risk to develop Alzheimer's disease and vice versa. A possible explanation is the cross-sequence interaction between A beta and amylin. Because the resulting amyloid oligomers are difficult to probe in experiments, we investigate stability and conformational changes of A beta amylin heteroassemblies through molecular dynamics simulations. We find that A beta is a good template for the growth of amylin and vice versa. We see water molecules permeate the beta-strand-turn-beta-strand motif pore of the oligomers, supporting a commonly accepted mechanism for toxicity of A beta-rich amyloid oligomers. Aiming for a better understanding of the physical mechanisms of cross-seeding and cell toxicity of amylin and A beta aggregates, our simulations also allow us to identify targets for the rational design of inhibitors against toxic fibril-like oligomers of A beta and amylin oligomers.