GRGETP is the inactive counterpart of GRGDTP, carrying glutamate in place of the aspartate that integrins recognise while retaining the threonine that distinguishes this pair from the serine-containing peptides. The supplied molecular weight exceeds that of GRGDTP by approximately 14, consistent with the single additional methylene group. Substituting aspartate for glutamate is the standard way to build an RGD negative control because it changes the ligand minimally in every respect except the one that matters. The aspartate carboxylate coordinates a divalent cation within the integrin binding site, and extending the side chain by one bond disrupts that geometry, so the peptide retains charge, mass and solubility behaviour while losing recognition. Matching the control to the active peptide matters more than it might appear. Because flanking residues influence which integrins engage a given RGD peptide, GRGETP is the correct comparator for GRGDTP specifically, just as GRGESP (LT1542) is the comparator for GRGDSP. Using a serine-containing control against a threonine-containing active peptide introduces a second variable and weakens the comparison, which is why both control variants are offered separately. | 