DNA Complexes with Cobalt(II) Phthalocyanine Disodium Disulfonate

Abstract

The interaction of cobalt phthalocyanine disodium disulfonate (CoPc) with calf thymus DNA in solutions was investigated by UV/vis spectrophotometry, circular dichroism (CD), and hydrodynamic methods (viscosity and flow birefringence). Two types of CoPc binding to DNA were observed. Fast CoPc interactions with DNA via external binding to phosphates were accompanied by the formation of stack-type phthalocyanine structures on the periphery of the DNA helix. The optical absorption spectra of such CoPc complexes with DNA were analyzed in order to obtain a binding constant K = (4.8 ± 0.4) × 104 M–1. CD spectra show the increasing optical activity of phthalocyanines bonded to DNA. DNA plays the role of a matrix, contributing to an increase in their stacking interactions. The CD spectrum of DNA varies slightly. The second type of cobalt-to-DNA binding manifests itself over a certain time. It can be associated with the reorganization of ligands in the cobalt coordination sphere by introducing DNA atoms. In our experiments, such binding was observed after storage of solutions for approximately 20 h at a temperature of 4 °C. It was shown that the minor groove of DNA remains free in CoPc–DNA complexes. CoPc does not bind with the most important group for metal coordinating to DNA in the major groove (N7 guanine). We completely excluded the intercalation binding model. The planes of phthalocyanines in CoPc–DNA complexes are oriented predominantly normal to the axis of the DNA helix. DNA rigidity (persistent length) does not change. This follows from the data on the measurement of the optical anisotropy and intrinsic viscosity of DNA in complexes.

PAMAM-calix-dendrimers: Synthesis and Thiacalixarene Conformation Effect on DNA Binding

“…This correlates well with the data obtained by fluorescence spectroscopy. As a result, the minimal effect of the G1-HCl on the CD spectra of the DNA indicates their external binding to the DNA phosphate groups [ 18 , 53 , 54 ]. Change in the nature of the effect (hyperchromia) with a growth in the bathochromic shift with an increase of the G1-HCl concentration made it possible to conclude that the structure of the complexes changed due to further binding along the DNA groove [ 55 ].…”

“…It can result from displacing the DAPI molecules by the macrocycles from the DNA groove. This mechanism explains quenching of the DAPI fluorescence in most works [53][54][55]. Thus, we assume that the G1-HCl form at least two types of complexes with DNA, i.e., by binding to the biopolymer at phosphate groups and in the groove.…”

Nanostructured Polyelectrolyte Complexes Based on Water-Soluble Thiacalix[4]Arene and Pillar[5]Arene: Self-Assembly in Micelleplexes and Polyplexes at Packaging DNA

“…The character of the binding could be easily controlled by adjusting the ratio of the dye and biopolymer [37]. Thus, we chose high concentration of the dye (1 dye molecule per DNA base pair), resulting in binding both in the minor groove and intercalation [38]. The interaction of the DAPI/CT-DNA system with the AP [5]A was first studied.…”

DNA Interaction with Coordination Compounds of Cd(II)containing 1,10-Phenanthroline

“…The synthesis of different metal complexes with phenanthroline ligands and the study of their binding to the DNA molecule have been carried out [11][12][13][14][15][16][17]. Some metal ions play an essential role in different biochemical functions.…”