Design and Synthesis of Porphyrin–Nitrilotriacetic Acid Dyads with Potential Applications in Peptide Labeling through Metallochelate Coupling

[Image: see text] The need to detect and monitor biomolecules, especially within cells, has led to the emerging growth of fluorescent probes. One of the most commonly used labeling techniques for this purpose is reversible metallochelate coupling via a nitrilotriacetic acid (NTA) moiety. In this study, we focus on the synthesis and characterization of three new porphyrin–NTA dyads, TPP-Lys-NTA, TPP-CC-Lys-NTA, and Py(3)P-Lys-NTA composed of a porphyrin derivative covalently connected with a modified nitrilotriacetic acid chelate ligand (NTA), for possible metallochelate coupling with Ni(2+) ions and histidine sequences. Emission spectroscopy studies revealed that all of the probes are able to coordinate with Ni(2+) ions and consequently can be applied as fluorophores in protein/peptide labeling applications. Using two different histidine-containing peptides as His(6)-tag mimic, we demonstrated that the porphyrin–NTA hybrids are able to coordinate efficiently with the peptides through the metallochelate coupling process. Moving one step forward, we examined the ability of these porphyrin–peptide complexes to penetrate and accumulate in cancer cells, exploring the potential utilization of our system as anticancer agents.