Peptide 12 inhibits endothelial cell adhesion to VEGFR-1 and directly supports cell adhesion. (A) Ribbon representation of the alpha carbon trace of VEGFR-1 dII structure determined by X-ray crystallography (PDB ID: 1flt). Peptides 1, 3, 5, 7, 9, and 11 (left panel) and 2, 4, 6, 8, 10, and 12 (right panel) are colored red, orange, yellow, blue, purple and magenta, respectively. Residues belonging to both peptide 5 and 7 (left panel) or 6 and 8 (right panel) are colored green. (B) Microtiter plates were coated with VEGFR-1/Fc or fibronectin (FN). HUVECs were preincubated with each peptide and then plated on the coated wells. Data are reported as percentage of adhesion, calculated relative to the number of cells attached on the same substrate in the absence of the peptides. (C) Different VEGFR-1 peptides and RGD peptide, as a positive control, were covalently linked to microtiter plates. HUVECs were then added to the coated plates and allowed to adhere. Nonspecific cell adhesion was measured by the absorbance in BSA-coated wells. Representative experiments performed in triplicate are shown; data are mean plus or minus SEM.