Recent experiments have identified peptides that adhere to GaAs and Si surfaces. Here, we use all-atom Monte Carlo simulations with implicit solvent to investigate the behavior in aqueous solution of four such peptides, all with 12 residues. At room temperature, we find that all four peptides are largely unstructured, which is consistent with experimental data. At the same time, we find that one of the peptides is structurally different and more flexible, as compared to the others. This finding points at structural differences as a possible explanation for differences in adhesion properties among these peptides. By also analyzing designed mutants of two of the peptides, an experimental test of this hypothesis is proposed.