A new peptide-based fluorescent probe selective for zinc(ii) and copper(ii)

Area of Science:

• Biochemistry
• Analytical Chemistry
• Molecular Biology

Background:

• Histidine-rich glycoproteins (HRGs) contain common five-residue repeats.
• Fluorescent probes are crucial for detecting metal ions in biological systems.
• Dansyl fluorophores exhibit Chelation Enhanced Fluorescence (CHEF) and solvatochromic effects.

Purpose of the Study:

• To design and characterize a novel fluorescent peptidyl-probe for metal ion detection.
• To investigate the probe's response to various metal ions, including Zn2+ and Cu2+.
• To evaluate the probe's potential for intracellular metal ion determination.

Main Methods:

• Design of a peptide probe (dH3w) incorporating a dansyl-amide moiety and a tryptophan residue.
• Utilizing fluorescence spectroscopy (steady-state) and isothermal titration calorimetry (ITC) for binding studies.
• Testing probe selectivity against a panel of biologically relevant metal ions.

Main Results:

• The dH3w probe demonstrated a selective fluorescence turn-on response to Zn2+.
• Two dH3w molecules bind to one Zn2+ ion with an association constant (Ka) of 5.7 × 10^5 M-1.
• The probe exhibited higher affinity for Cu2+ (Ka = 1.2 × 10^6 M-1), causing fluorescence quenching.
• dH3w successfully penetrated HeLa cells, enabling intracellular metal ion detection.

Conclusions:

• The designed dH3w probe is effective for selective detection of Zn2+ and Cu2+.
• The probe's mechanism involves fluorescence resonance energy transfer (FRET) and CHEF/solvatochromic effects.
• dH3w holds promise for real-time monitoring of intracellular Zn2+ and Cu2+ concentrations.