H-Arg-Gly-Asp-Cys-OH is a tetrapeptide that contains the arginine-glycine-aspartate (RGD) motif, a sequence that acts as a recognition site for various adhesion proteins.1It inhibits the binding of fibrinogen to endothelial cells and ADP-stimulated platelets with IC50values of 320 and 35 μM, respectively.2Implantation of titanium rods coated with H-Arg-Gly-Asp-Cys-OH increases bone formation in rat femurs.3H-Arg-Gly-Asp-Cys-OH has been conjugated to polyethylenimine to improve gene transfection efficiency.4 1.Park, H.S., Kim, C., and Kang, Y.K.Preferred conformations of RGDX tetrapeptides to inhibit the binding of fibrinogen to plateletsBiopolymers63(5)298-313(2002) 2.Tranqui, L., Andrieux, A., Hudry-Clergeon, G., et al.Differential structural requirements for fibrinogen binding to platelets and to endothelial cellsJ. Cell Biol.108(6)2519-2527(1989) 3.Ferris, D.M., Moodie, G.D., Dimond, P.M., et al.RGD-coated titanium implants stimulate increased bone formation in vivoBiomaterials20(23-24)2323-2331(1999) 4.Kunath, K., Merdan, T., Hegener, O., et al.Integrin targeting using RGD-PEI conjugates for in vitro gene transferJ. Gene Med.5(7)588-599(2003)