The structure of the 21-30 fragment of the amyloid beta-protein (A beta) was investigated by ion mobility mass spectrometry and replica exchange dynamics simulations. Mutations associated with familial Alzheimer's disease (E22G, E22Q E22K, and D23N) of A beta(21-30) were also studied, in order to understand any structural changes that might occur with these substitutions. The structure of the WT peptide shows a bend and a perpendicular turn in the backbone which is maintained by a network of D23 hydrogen bonding. Results for the Mutants show that substitutions at E22 do little to alter the overall Structure of the fragment. A substitution at D23 resulted in a change of structure for A beta(21-30). A comparison of these gas-phase studies to previous solution-phase studies reveals that the peptide can fold in the absence of solvent to a structure also seen in solution, highlighting the important role of the D23 hydrogen bonding network in stabilizing the fragment's folded structure.