DNA binding studies of PdCl2(LL)(LL = chelating diamine ligand: N,N-dimethyltrimethylenediamine) complex

Abstract

The interaction of native calf thymus DNA with the Pd(II) complex, PdCl2(LL) (LL = chelating diamine ligand: N,N-dimethyltrimethylenediamine), in 10 mM Hepes aqueous solutions at neutral pH has been monitored as a function of metal complex/DNA molar ratio by UV absorption spectrophotometry, circular dichroism (CD), viscosimetry, and fluorescence spectroscopy. The results support two modes of interaction. In particular, this complex showed absorption hypochromism and then hyperchromism, increase in melting temperature, and some structural changes in specific viscosity when bound to calf thymus DNA. The binding constant determined using absorption measurement is 2.69.10(3) M(-1). As evidenced by the increasing fluorescence of methylene blue-DNA solutions in the presence of increasing amounts of metal complex, PdCl(2)(LL) is able to displace the methylene blue intercalated into DNA, but not so completely, as indicated by partial intercalation. CD spectral changes in two steps and viscosity decrease confirm our conclusions.

DNA-binding study of anthraquinone derivatives using Chemometrics methods

“…The molar ellipticity was determined as [Q] ¼ (Q Â 100MRW)/(cl), where c is DNA concentration in mg/ml, l is the light path length in centimetre, and Q is the measured ellipticity in degree at wavelength l. The instrument was calibrated with (þ)-10-Camphorsulfonate assuming [Q] 291 ¼ 7820 deg cm 2 dmol À1 and with Jasco standard non hygroscopic ammonia, (þ)-10-Camphorsulfonate assuming [Q] 290.5 ¼ 7910 deg cm 2 dmol À1 . Noise in the data was smoothed using the Jasco J-810 software including the fast Fourier transform noise reduction routine which allowed enhancement of most noisy spectra without distorting their peak shape [59].…”

“…t dye , t control and t 0 are the average flow times for the DNAedye, free DNA and buffer, respectively. Then, the ðh=h Þ 1=3 values were plotted versus [dye)]/[DNA] ratio [59]. The UV data were preprocessed using MATLAB software, version 7.1 (Mathworks, Natick, USA), and the deconvolution of the obtained data matrix was performed using the INDICES, PCA, nonlinear least-squares analysis and EQUISPEC softwares that work in S-Plus, MATLAB, Solver of Excel and MATLAB media, respectively.…”

“…Partial intercalation of dye into DNA base pairs is characterized by a minor red shift and decrease in UVevis spectra intensity [59]. These changes are typical of a complex bound to DNA through partially intercalation involving partially insertion of the aromatic chromophore of the quinizarin, and danthron ligands between the base pairs of DNA when R i s are greater than one.…”

“…Disodium salt of CT-DNA was prepared and stored at 4 C. The stock solution of DNA was prepared in accordance with previous work [59]. A solution of CT-DNA gave a ratio of UV absorbance at 260 and 280 nm more than 1.9, indicating that DNA was sufficiently free from protein.…”

“…A solution of CT-DNA gave a ratio of UV absorbance at 260 and 280 nm more than 1.9, indicating that DNA was sufficiently free from protein. The concentration (monomer units) of the DNA stock solution (1.0 mM per nucleotide) was determined by UV spectrophotometry, in properly diluted samples, using the molar absorption coefficient 6600 M À1 cm À1 at 260 nm [59]. Stock solutions were stored at 4 C and were used no more than 4 days.…”