Amyloids are associated with-diseases,, including Alzheimer's, as well as functional roles such as storage of peptide hormones. It is still unclear what differences exist between-aberrant and functional amyloids. However, it is known that soluble oligomers formed during amyloid aggregation are more toxic than the final fibrils. Here, we perform molecular dynamics simulations to study the aggregation of the amyloid-beta peptide A beta(25-35),, associated with Alzheimer's disease, and two functional amyloid-forming tachykinin peptides: kassinin and neuromedin K. Although the three peptides have similar primary sequences, tachykinin. peptides,in contrast to A beta(25-35), font nontoxic amyloids. Our simulations reveal that the charge, of the C-terminus is essential to controlling the aggregation process. In particular, when the kassinin C-terminus is not amidated, the aggregation kinetics decreases considerably. in addition, we observe that the monomeric peptides in extended conformations aggregate faster than those in,collapsed hairpin-like conformations.