N-terminal acetylation is a commonly used modification technique for synthetic peptides， mostly applied for reasons of enhanced stability， and in many cases regarded as inconsequential. In engineered biosilification - the controlled deposition of silica for nanotechnology applications by designed peptides - charged groups often play a deciding role. Here we report that changing the charge by acetylation of a 14-amino acid leucine-lysine (LK) peptide dramatically changes the morphology of precipitated biosilica; acetylated LK peptides produce nano-spheres， whereas nano-wires are precipitated by the same peptide in a non-acetylated form. By using interface-specific vibrational spectroscopy and coarse-grained molecular simulations， we show that this change in morphology is not the result of modified peptide-silica interactions， but rather caused by the stabilization of the hydrophobic core of peptide aggregates created by the removal of a peptide charge upon acetylation. These results should raise awareness of the potential impact of N-terminal modifications in peptide applications. Copyright © 2016 European Peptide Society and John Wiley & Sons， Ltd.