DMNP as an Effective Cage for Ln³⁺: A Spectroscopic and Thermodynamic Study

Area of Science:

• Biochemistry
• Chemical Biology
• Photochemistry

Background:

• Dimethoxynitrophenyl-EDTA (DMNP) is a common calcium (Ca2+) cage for in vivo signaling studies.
• Lanthanides (Ln3+) mimic Ca2+ coordination, enabling potential fluorescence and NMR applications.

Purpose of the Study:

• To investigate the binding of Tb3+, Eu3+, and Nd3+ to DMNP.
• To characterize the release kinetics and thermodynamics of Ca2+, Mg2+, and Tb3+ from DMNP after photoactivation.

Main Methods:

• Isothermal titration calorimetry (ITC) to determine binding constants.
• Photothermal beam deflection (PBD) to study ion release kinetics and thermodynamics.

Main Results:

• Tb3+, Eu3+, and Nd3+ bind DMNP with high affinity (1:1 ratio, K11 ~10^12 M-1).
• Photodissociation rapidly releases caged ions (<10 μs).
• Ca2+ rebinding to unphotolyzed DMNP observed at subsaturating concentrations (300 μs lifetime).

Conclusions:

• DMNP is an effective photolabile cage for oxophilic lanthanides.
• This expands DMNP's utility for studying Ca2+-related processes using Ln3+ biomimetics.