| Autor: |
Gonzalez WG; Department of Chemistry and Biochemistry and Biomolecular Sciences Institute, Florida International University, Miami, Florida 33199, United States., Sakhdari S; Department of Chemistry and Biochemistry and Biomolecular Sciences Institute, Florida International University, Miami, Florida 33199, United States., Alam MS; Department of Chemistry and Biochemistry and Biomolecular Sciences Institute, Florida International University, Miami, Florida 33199, United States., Dhulipala G; Department of Chemistry and Biochemistry and Biomolecular Sciences Institute, Florida International University, Miami, Florida 33199, United States., Kavallieratos K; Department of Chemistry and Biochemistry and Biomolecular Sciences Institute, Florida International University, Miami, Florida 33199, United States., Miksovska J; Department of Chemistry and Biochemistry and Biomolecular Sciences Institute, Florida International University, Miami, Florida 33199, United States. |
| Abstrakt: |
Dimethoxynitrophenyl-EDTA (DMNP) is a popular calcium cage that is frequently used to investigate the role of Ca 2+ in signaling processes in vivo . Lanthanides have been used in Ca 2+ biomimetics due to similarities in coordination properties of Ln 3+ and Ca 2+ that may enable fluorescence and NMR studies of functional and structural properties of Ca 2+ binding proteins. In this study, we show that Tb 3+ , Eu 3+ , and Nd 3+ bind strongly to DMNP in a 1:1 ratio. Isothermal titration calorimetric measurements of Ca 2+ displacement by Ln 3+ in DMNP provide the equilibrium binding constants for Ln 3+ DMNP complexation with association constants, K 11 = (1.2 ± 0.7) × 10 12 M -1 for Eu 3+ , (2.5 ± 1.7) × 10 12 M -1 for Nd 3+ , and (2.8 ± 0.8) × 10 12 M -1 for Tb 3+ . The kinetics and thermodynamics of Ca 2+ , Mg 2+ , and Tb 3+ release from DMNP were characterized using photothermal beam deflection (PBD). Ligand release from the DMNP cage was rapid and occurred within 10 μs upon cage photofragmentation and was associated with similar reaction volume and enthalpy changes that can be attributed to the photoreleased ion solvation. In the case of Ca 2+ DMNP photodissociation at subsaturating Ca 2+ concentrations, we observed a slower phase with a lifetime of 300 μs that we attribute to Ca 2+ rebinding to unphotolyzed DMNP. These results demonstrate that DMNP can serve as an effective photolabile cage for oxophilic Ln 3+ that has similar coordination properties to Ca 2+ and Mg 2+ . |
