6533b86efe1ef96bd12ccab3
RESEARCH PRODUCT
A Theoretical and Experimental Investigation of the Spectroscopic Properties of a DNA-Intercalator Salphen-Type ZnIIComplex
Tarita BiverAzzurra BurgalassiGiampaolo BaroneAngelo SpinelloAlessio TerenziAlessandro BiancardiBenedetta Mennuccisubject
spectroscopyNO ligandStereochemistryIntercalation (chemistry)Ionic bondingmetal complex Fluorescence spectroscopy DNA recognition metal complexes organometallics complex formation DNA binding drugs fluorescence spectroscopy equilibrium constants reaction mechanisms nucleic acids affinity binding mode thermodynamics speciationmetal complexesbinding modePhenylenediaminesPolarizable continuum modelCatalysisdrugsmetal complexthermodynamicsintercalationcomplex formationOrganometallic CompoundsA-DNADNA bindingFluorescence spectroscopyDNA recognitionphotochemistryLigandChemistrySpectrum AnalysisphotooxidationOrganic ChemistryCationic polymerizationequilibrium constantsGeneral Chemistrydensity functional calculationFluorescenceZincCrystallographyreaction mechanismsnucleic acidsspeciationSettore CHIM/03 - Chimica Generale E InorganicaExcited stateaffinityfluorescenceorganometallicsdescription
The photophysical and DNA-binding properties of the cationic zinc(II) complex of 5-triethylammonium methyl salicylidene ortho-phenylenediiminato (ZnL 2 + ) were investi- gated by a combination of experimental and theoretical methods. DFT calculations were performed on both the ground and the first excited states of ZnL 2 + and on its possi- ble mono- and dioxidation products, both in vacuo and in selected solvents mimicked by the polarizable continuum model. Comparison of the calculated absorption and fluores- cence transitions with the corresponding experimental data led to the conclusion that visible light induces a two-elec- tron photooxidation process located on the phenylenediimi- nato ligand. Kinetic measurements, performed by monitor- ing absorbance changes over time in several solvents, are in agreement with a slow unimolecular photooxidation pro- cess, which is faster in water and slower in less polar sol- vents. Moreover, structural details of ZnL-DNA binding were obtained by DFT calculations on the intercalation complexes between ZnL and the d(ApT)2 and d(GpC)2 dinucleoside monophosphate duplexes. Two main complementary bind- ing interactions are proposed: 1) intercalation of the central phenyl ring of the ligand between the stacked DNA base pairs; 2) external electrostatic attraction between the nega- tively charged phosphate groups and the two cationic trie- thylammonium groups of the Schiff-base ligand. Such sug- gestions are supported by fluorescence titrations performed on the ZnL/DNA system at different ionic strengths and tem- peratures. In particular, the values of the DNA-binding con- stants obtained at different temperatures provided the en- thalpic and entropic contributions to the binding and con- firmed that two competitive mechanisms, namely, intercala- tion and external interaction, are involved. The two mecha- nisms are coexistent at room temperature under physiological conditions.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2014-01-01 |