Next, the reactivity of 3b is investigated towards various peptidic substrates. Besides K', we chose the hexapeptide KFRGDS and the pentapeptide GRGDS. This way, we could probe lysine and glycine reactivity with minimal changes of the overall peptide structure. Both peptides comprise the characteristic RGD sequence that enables the adhesion of cells to a foreign substrate via transmembrane integrin binding. The covalent attachment of RGD sequences in low amounts towards networks, surfaces and polymers is a vital condition to facilitate cell-matrix interactions of biohybrid materials. As a third candidate, we chose to investigate the reactivity of KLVFF towards 3b, representing a rather hydrophobic peptide. The peptide sequence KLVFF is a short fragment of the amyloid β-peptide (Aβ) that promotes Aβ-Aβ interactions, which can result in the formation of amyloid fibrils. As peptides or protein modifications are usually carried out at lower concentrations, we adjusted accordingly (1 mM) and used reactant ratios of 1:1.1:1.1 (3b-nucleophile-NMM). The reactions were carried out in a vial wherefrom regular injections into our HPLC system yielded corresponding kinetic data of the reactions. As reaction media we used 10 mM PBS (pH = 7.4) or a sodium phosphate buffer (NaPi, pH = 8.0). All products were further characterized by mass spectrometry.