The membrane binding and model lipid raft interaction of synthetic peptides derived from the caveolin scaffolding domain (CSD) of the protein caveolin-1 have been investigated. CSD peptides bind preferentially to liquid-disordered domains in model lipid bilayers composed of cholesterol and an equimolar ratio of dioleoylphosphatidylcholine (DOPC) and brain sphingomyelin. Three caveolin-1 peptides were studied: the scaffolding domain (residues 83-101), a water-insoluble construct containing residues 89-101, and a water-soluble construct containing residues 89-101. Confocal and fluorescence microscopy investigation shows that the caveolin(-1) peptides bind to the more fluid cholesterol-poor phase. The binding of the water-soluble peptide to lipid bilayers was measured using fluorescence correlation spectroscopy (FCS). We measured ntolar partition coefficients of 10(4) M-1 between the soluble peptide and phase- separated lipid bilayers and 10(3) M-1 between the soluble peptide and bilayers with a single liquid phase. Partial phase diagrams for our phase- separating lipid mixture with added caveolin(-1) peptides were measured using fluorescence microscopy. The water-SOILible pepticle did not change the phase morphology or the miscibility transition in giant unilarnellar vesicles (GUVs); however, the water-insoluble and full-length CSD peptides. lowered the liquid-liquid melting temperature. (c) 2006 Elsevier Inc. All rights reserved.