GRGDSPK is an inhibitory peptide for RGD-mediated adhesion between integrin and extracellular matrix molecules. Sequence: Gly-Arg-Gly-Asp-Ser-Pro-Lys. In Vitro: GRGDSPK inhibits the adhesion of Rat PDL cells^[1]. RGD-containing (GRGDSPK, 1.5 mM, 1.0 mM, and 0.5 mM) and RGD-mod-ified peptides impair the ability of sperm to fertilizebovine oocytes, illustrated by a reduction in cleavage in a dose-dependent manner^[2].