DNA as a Catalyst and Catalytic Template for the Racemisation of Metal Tris-Phenanthroline Complexes

Rodger, Alison; Nordén, Bengt; Rodger, P. Mark; Bates, Paula J.

doi:10.1002/1099-0682(20021)2002:1<49::aid-ejic49>3.0.co;2-8

Cited by 12 publications

(6 citation statements)

References 16 publications

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“…Circular Dichroic Spectral Studies. On addition of rac -[Ru(5,6-dmp) 3 ] 2+ complex to CT DNA (2 × 10 -5 M, 1/ R = 0−2 = [Ru complex]/[DNA]), the characteristic bands − of DNA due to base stacking (275 nm) and that due to right-handed helicity (248 nm) disappear and a biphasic CD signal with positive (270 nm) and negative (280 nm) maxima and a zero cross over at 275 nm are observed. A small negative (240 nm) and a positive signal (248 nm) with a cross over at 245 nm are also observed.…”

Section: Resultsmentioning

confidence: 99%

Interaction of rac-[Ru(5,6-dmp)₃]²⁺ with DNA: Enantiospecific DNA Binding and Ligand-Promoted Exciton Coupling

et al. 2005

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The X-ray crystal structure of the complex rac-[Ru(5,6-dmp)(3)]Cl(2) (5,6-dmp = 5,6-dimethyl-1,10-phenanthroline) reveals a distorted octahedral coordination geometry with the Ru-N bond distances shorter than in its phen analogue. Absorption spectral titrations with CT DNA reveal that rac-[Ru(5,6-dmp)(3)](2+) interacts (K(b), (8.0 +/- 0.2) x 10(4) M(-1)) much more strongly than its phen analogue. The emission intensity of the 5,6-dmp complex is dramatically enhanced on binding to DNA, which is higher than that of the phen analogue. Also, interestingly, time-resolved emission measurements on the DNA-bound complex shows biexponential decay of the excited states with the lifetimes of short- and long-lived components being higher than those for the phen analogue. The CD spectral studies of rac-[Ru(5,6-dmp)(3)](2+) bound to CT DNA provide a definite and elegant evidence for the enantiospecific interaction of the complex with B-form DNA. Competitive DNA binding studies using rac-[Ru(phen)(3)](2+) provide support for the strong binding of the complex with DNA. The Delta-enantiomer of rac-[Ru(5,6-dmp)(3)](2+) binds specifically to the right-handed B-form of poly d(GC)(12) at lower ionic strength (0.05 M NaCl), and the Lambda-enantiomer binds specifically to the left-handed Z-form of poly d(GC)(12) generated by treating the B-form with 5 M NaCl. The strong electronic coupling of the DNA-bound complex with the unbound complex facilitates the change in its enantiospecificity upon changing the conformation of DNA. The (1)H NMR spectra of rac-[Ru(5,6-dmp)(3)](2+) bound to poly d(GC)(12) reveal that the complex closely interacts most possibly in the major grooves of DNA. Electrochemical studies using ITO electrode show that the 5,6-dmp complex stabilizes CT DNA from electrocatalytic oxidation of its guanine base more than the phen analogue does.

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Section: Resultsmentioning

confidence: 99%

Interaction of rac-[Ru(5,6-dmp)₃]²⁺ with DNA: Enantiospecific DNA Binding and Ligand-Promoted Exciton Coupling

et al. 2005

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“…A similar ICD behavior is expected for the partially intercalating rac-[Co(dpq) 3 ] 2+ 3 and rac-[Ni(dpq) 3 ] 2+ 6 upon DNA binding. However, interestingly, the CD band characteristic of DNA helicity disappears (Figures S5 and S6 †) and the base stacking band is replaced by a biphasic CD signal 59 with positive (~250 nm) and negative (3, 258; 6, 263 nm) maxima and the zero cross-over point (259 nm) corresponding to the l max of the p-p* transition located on the dpq ligand. Additional negative bands are observed, suggesting changes in the structure of the DNA base stack.…”

Section: Circular Dichroic Spectral Studiesmentioning

confidence: 99%

“…2 ] 2+ , but additional experiments are needed to confirm this.Upon addition of rac-[Co(5,6-dmp) 3 ] 2+ 2 to CT DNA (1/R = [Co]/[DNA] = 2) the CD band characteristic of DNA helicity disappears (Fig.4) and the base stacking band is split into a biphasic CD signal59 with positive (262 nm) and negative (294 nm) maxima and the zero cross-over point (280 nm) corresponding to the l max of the p-p* transition located on the 5,6-dmp ligand is observed. Similar observations are made for rac-[Ni(5,6-dmp) 3 ] 2+ 5 bound to CT DNA.…”

mentioning

confidence: 99%

Interaction of rac-[M(diimine)3]2+ (M = Co, Ni) complexes with CT DNA: role of 5,6-dmp ligand on DNA binding and cleavage and cytotoxicity

et al. 2011

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The complexes [Co(diimine)(3)](ClO(4))(2)1-3 and [Ni(diimine)(3)](ClO(4))(2)4-6, where diimine = 1,10-phenanthroline (phen) (1,4), 5,6-dimethyl-1,10-phenanthroline (5,6-dmp) (2,5) and dipyrido[3,2-d:2',3'-f]quinoxaline (dpq) (3,6), have been isolated, characterized and their interaction with CT DNA studied by using a host of physical methods. The X-ray crystal structures of rac-[Co(5,6-dmp)(3)](ClO(4))(2)2 and rac-[Ni(5,6-dmp)(3)](ClO(4))(2)5 have been determined and the isostructural and also isomorphous complex cations possess distorted octahedral coordination geometries. The absorption spectral titrations of the complexes with DNA reveal that the CT DNA binding affinity (K(b)) of the complexes varies as 3>2>1; 6>5>4. The Ni(II) complexes display DNA binding stronger than the corresponding Co(II) analogues, which is expected of their bigger sizes. The higher DNA binding affinity of 3 and 6 is due to the involvement in partial insertion of the extended phen ring in between the DNA base pairs. In contrast, 2 and 5 interact with DNA in the major groove through hydrophobic forces involving the methyl groups on the 5,6 positions of phen ring. An enhancement in relative viscosities of DNA upon binding to 1-6 is consistent with the DNA binding affinities. The CD spectral studies show only an induced CD band on the characteristic positive band of CT DNA for both the phen (1,4) complexes. In contrast, the 5,6-dmp (2,5) and dpq (3,6) complexes bound to CT DNA exhibit biphasic CD signals in place of the positive CD band and the negative helicity band disappears. This reveals that the complexes bind to DNA enantiopreferentially and effect changes in secondary structure of DNA. The CV and DPV responses indicate that the DNA-bound dpq complexes are stabilized in the lower oxidation state of Co(II) more than in the Co(III) oxidation state. The prominent DNA cleavage abilities of 1-3 observed in the presence of H(2)O(2) (200 μM) follows the order 2>1>3 with efficiencies of more than 90% even at 10 μM complex concentration. Interestingly, Ni(II) complexes 4-6 exhibit higher cytotoxicity (IC(50): 1, 28.0; 2, 15.0; 3, 20.0; 4, 8.0; 5, 2.0; 6, 2.0 μM at 48 h; IC(50): 1, 30.0; 2, 20.0; 3, 25.0; 4, 10.0; 5, 3.0; 6, 3.0 μM at 24 h) against human breast cancer (MCF 7) cell lines than the Co(II) complexes 1-3 as well as cisplatin in spite of their inability to cleave DNA. Also, the 5,6-dmp complex 5 shows cytotoxicity higher than the dpq complex 6 at 24 h incubation time and both 5 and 6 display apoptotic and necrotic modes of cell death.

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“…Thus the stereoelectronic factors of the tris-diimine complexes determine their DNA binding affinities. bands disappear and a new biphasic CD signal 39 with positive (270 nm) and negative (280 nm) maxima and zero cross-over at 275 nm are observed. Another biphasic CD signal with a negative (240 nm) and positive maxima (248 nm) and a zero cross-over at 245 nm is also observed.…”

Section: Description Of Structures Of Rac-[cu(56-dmp) 3 ](Clo 4 ) 2 2...mentioning

confidence: 99%

Interaction of rac-[Cu(diimine)3]2+ and rac-[Zn(diimine)3]2+ complexes with CT DNA: effect of fluxional Cu(ii) geometry on DNA binding, ligand–promoted exciton coupling and prominent DNA cleavage

Ramakrishnan

Palaniandavar

2008

Dalton Trans.

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The complexes [Cu(phen)(3)](ClO(4))(2) 1, [Cu(5,6-dmp)(3)](ClO(4))(2) 2, [Cu(dpq)(3)](ClO(4))(2) 3, [Zn(phen)(3)](ClO(4))(2) 4, [Zn(5,6-dmp)(3)](ClO(4))(2) 5 and [Zn(dpq)(3)](ClO(4))(2) 6, where phen = 1,10-phenanthroline, 5,6-dmp = 5,6-dimethyl-1,10-phenanthroline and dpq = dipyrido[3,2-d:2',3'-f]quinoxaline, have been isolated, characterized and their interaction with calf thymus DNA studied by using a host of physical methods. The X-ray crystal structures of rac-[Cu(5,6-dmp)(3)](ClO(4))(2) and rac-[Zn(5,6-dmp)(3)](ClO(4))(2) have been determined. While 2 possesses a regular elongated octahedral coordination geometry (REO), 5 possesses a distorted octahedral geometry. Absorption spectral titrations of the Cu(II) complexes with CT DNA reveal that the red-shift (12 nm) and DNA binding affinity of 3 (K(b), 7.5 x 10(4) M(-1)) are higher than those of 1 (red-shift, 6 nm; K(b), 9.6 x 10(3) M(-1)) indicating that the partial insertion of the extended phen ring of dpq ligand in between the DNA base pairs is deeper than that of phen ring. Also, 2 with a fluxional Cu(II) geometry interacts with DNA (K(b), 3.8 x 10(4) M(-1)) more strongly than 1 suggesting that the hydrophobic forces of interaction of 5,6 methyl groups on the phen ring is more pronounced than the partial intercalation of phen ring in the latter with a static geometry. The DNA binding affinity of 1 is lower than that of its Zn(ii) analogue 4, and, interestingly, the DNA binding affinity 2 of with a fluxional geometry is higher than that of its Zn(II) analogue 5 with a spherical geometry. It is remarkable that upon binding to DNA 3 shows an increase in viscosity higher than that the intercalator EthBr does, which is consistent with the above DNA binding affinities. The CD spectra show only one induced CD band on the characteristic positive band of CT DNA upon interaction with the phen (1,4) and dpq (3,6) complexes. In contrast, the 5,6-dmp complexes 2 and 5 bound to CT DNA show exciton-coupled biphasic CD signals with 2 showing CD signals more intense than 5. The Delta-enantiomer of rac-[Cu(5,6-dmp)(3)](2+) 2 binds specifically to the right-handed B-form of CT DNA at lower ionic strength (0.05 M NaCl) while the Lambda-enantiomer binds specifically to the left-handed Z-form of CT DNA generated by treating the B-form with 5 M NaCl. The complex 2 is stabilized in the higher oxidation state of Cu(II) more than its phen analogue 1 upon binding to DNA suggesting the involvement of electrostatic forces in DNA interaction of the former. In contrast, 3 bound to DNA is stabilized as Cu(I) rather than the Cu(II) oxidation state due to partial intercalative interaction of the dpq ligand. The efficiencies of the complexes to oxidatively cleave pUC19 DNA vary in the order, 3> 1 >> 2 with 3 effecting 100% cleavage even at 10 microM complex concentration. However, interestingly, this order is reversed when the DNA cleavage is performed using H(2)O(2) as an activator and the highest cleavage efficiency of 2 is ascribed to its electrostatic interaction with the exterior phos...

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DNA as a Catalyst and Catalytic Template for the Racemisation of Metal Tris-Phenanthroline Complexes

Cited by 12 publications

References 16 publications

Interaction of rac-[Ru(5,6-dmp)₃]²⁺ with DNA: Enantiospecific DNA Binding and Ligand-Promoted Exciton Coupling

Interaction of rac-[Ru(5,6-dmp)₃]²⁺ with DNA: Enantiospecific DNA Binding and Ligand-Promoted Exciton Coupling

Interaction of rac-[M(diimine)3]2+ (M = Co, Ni) complexes with CT DNA: role of 5,6-dmp ligand on DNA binding and cleavage and cytotoxicity

Interaction of rac-[Cu(diimine)3]2+ and rac-[Zn(diimine)3]2+ complexes with CT DNA: effect of fluxional Cu(ii) geometry on DNA binding, ligand–promoted exciton coupling and prominent DNA cleavage

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DNA as a Catalyst and Catalytic Template for the Racemisation of Metal Tris-Phenanthroline Complexes

Cited by 12 publications

References 16 publications

Interaction of rac-[Ru(5,6-dmp)3]2+ with DNA: Enantiospecific DNA Binding and Ligand-Promoted Exciton Coupling

Interaction of rac-[Ru(5,6-dmp)3]2+ with DNA: Enantiospecific DNA Binding and Ligand-Promoted Exciton Coupling

Interaction of rac-[M(diimine)3]2+ (M = Co, Ni) complexes with CT DNA: role of 5,6-dmp ligand on DNA binding and cleavage and cytotoxicity

Interaction of rac-[Cu(diimine)3]2+ and rac-[Zn(diimine)3]2+ complexes with CT DNA: effect of fluxional Cu(ii) geometry on DNA binding, ligand–promoted exciton coupling and prominent DNA cleavage

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Interaction of rac-[Ru(5,6-dmp)₃]²⁺ with DNA: Enantiospecific DNA Binding and Ligand-Promoted Exciton Coupling

Interaction of rac-[Ru(5,6-dmp)₃]²⁺ with DNA: Enantiospecific DNA Binding and Ligand-Promoted Exciton Coupling