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

Abstract

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 Ni2+ ions and histidine sequences. Emission spectroscopy studies revealed that all of the probes are able to coordinate with Ni2+ ions and consequently can be applied as fluorophores in protein/peptide labeling applications. Using two different histidine-containing peptides as His6-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.

A short guide on blue fluorescent proteins: limits and perspectives

“…The modification of residues at the oligomeric interface can produce monomeric variants of NADPH-dependent BFPs, although this variant can bind a single NADPH, which results in a decrease in fluorescence or the loss of avidity. NADPH-dependent BFPs can be fused with proteins of low molecular weight or oligopeptide tags with an amorphous structure such as signal sequences (Glymenaki et al 2022 ; Kreissl et al 2023 ). However, most physiologically important proteins are multimers or have multiple domains, meaning that this option is not really feasible.…”

Enhanced optical imaging and fluorescent labeling for visualizing drug molecules within living organisms

“…However, most targets identified for fluorescence derivatives have been uncovered through blind screening, resulting in a low success rate and unexpected outcomes. To enhance signal-to-noise ratios and enable dynamic imaging, reversible chemical selection and catalytic processes with signal amplification offer promising solutions, in contrast to the prevailing irreversible chemical connections 165 , 166 , 167 . Nonetheless, challenges such as off-target effects and false positives persist in the clinical application of fluorescent drugs.…”

Porphyrins—valuable pigments of life

“…Coutsolelos and co-workers reported the synthesis and characterization of three porphyrin-based fluorescent probes (Figure 10), bearing modified lysine-NTA groups and could be applied in protein labelling through metallochelate coupling chemistry (Glymenaki et al, 2022). All hybrids were based on a free base porphyrin macrocycle which was covalently connected with an appropriately NTAsubstituted ligand.…”

“…Similarly to the latter example, water insoluble tetraphenylporphyrins bearing a single carboxyalkyl side-arm were synthesized, showing remarkable photostability and a nearly 90% photokilling efficiency toward cancer cells (Panagiotakis et al, 2022). We have also examined the ability of porphyrin-peptide hybrids as labelling agents, in order to potentially be tested as theragnostic agents (Glymenaki et al, 2022). Finally, peptide nucleic acids (PNAs) were connected to photosensitizers (bodipy and porphyrin) to develop compounds for photodynamic therapy (PDT) (Chang et al, 2020).…”