Tethered lipid bilayers were formed on oxidized Si surfaces using the avidin-biotin interaction to investigate the lipid membrane protein interactions by using gramicidin-A (g-A) as a model membrane protein. The morphology of the tethered lipid bilayer, observed by in situ atomic force microscopy (AFM), changed drastically by the reconstruction of g-A. The aggregation behavior of g-A was clearly different in the tethered membrane from those in simple supported membranes on mica and SiO2 surfaces. (c) 2006 Elsevier B.V. All rights reserved.