A combination of circular dichroism and solution H-1 NMR spectroscopy provides a localized description of the distribution of alpha-helical structure within the capped peptide DDDDAAAAARRRR (4DAR5) in aqueous solution and adsorbed onto anionic and cationic colloidal substrates. The adsorption-induced conformational changes are different from those observed upon heating 4DAR5 in solution, in which case the alarline segment remains largely alpha-helical and the transition to a coil structure propagates from the termini. Adsorption is driven by electrostatic complementarity, which places the charged peptide segment adjacent to the substrate of opposite charge. A similar pattern of alpha-helicity loss is observed whether the peptide is adsorbed onto anionic or cationic colloidal silica, despite inverse orientations; significant alpha-helicity loss occurs within the central alanine segment and the terminal arginine segment, whereas alpha-helicity is retained in the aspartate segment. This pattern of adsorption-induced conformational change illustrates the complex and subtle balance among the intramolecular and intermolecular factors that influence the conformations of adsorbed peptides and proteins. (C) 2003 Elsevier Science (USA). All rights reserved.