This peptide is the inactive comparator for GRGDSP. The only difference is at the fourth position, where the aspartate of the active sequence is replaced by glutamate, and the supplied molecular weights differ by approximately 14, the mass of the single additional methylene group that distinguishes the two side chains. That one extra carbon is enough to abolish integrin recognition. The carboxylate of the aspartate coordinates a divalent cation in the integrin metal-ion-dependent adhesion site, and the geometry of that contact is tightly constrained, so lengthening the side chain by a single bond displaces it from the binding pocket. RGE peptides consequently do not compete for integrin binding, and studies comparing GRGDSP against GRGESP use exactly this pairing to establish that an effect is integrin-mediated. The reason to buy this peptide rather than simply omitting a treatment is that it controls for everything the active peptide does apart from binding: the same charge, near-identical mass, the same handling and solubility behaviour, the same osmotic and vehicle contribution at matched concentration. A no-peptide control does not account for those. Where a result is intended to demonstrate integrin dependence, reviewers will generally expect this comparator to be present rather than a blank. | 