Study binding of Al-curcumin complex to ds-DNA, monitoring by multispectroscopic and voltammetric techniques

Study of DNA interactions with bifenthrin by spectroscopic techniques and molecular modeling

The interaction between bifenthrin (BF) and calf thymus DNA (ctDNA) in physiological buffer (pH 7.4) was investigated by UV-vis absorption, fluorescence, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy, coupled with viscosity measurements and molecular docking techniques. It was found that BF molecular could intercalate into the base pairs of ctDNA as evidenced by significant increases in absorption intensity, fluorescence polarization and relative viscosity of ctDNA, decrease in iodide quenching effect, and induced CD spectral changes. The association constant of BF with ctDNA was evaluated to be in the order of 10(4) L mol(-1). Thermodynamic analysis of the binding data obtained at different temperatures suggested that the binding process was primarily driven by hydrogen bonds and van der Waals forces, as the values of the enthalpy change (ΔH) and the entropy change (ΔS) were calculated to be -31.13±1.89 kJ mol(-1) and -22.79±1.21 J mol(-1) K(-1), respectively. The results of FT-IR spectra and molecular docking showed that a specific binding mainly existed between BF and adenine and guanine bases.

Proposed model for in vitro interaction between fenitrothion and DNA, by using competitive fluorescence, (31)P NMR, (1)H NMR, FT-IR, CD and molecular modeling

In this work we proposed a model for in vitro interaction of fenitrothion (FEN) with calf thymus-DNA by combination of multispectroscopic and two dimensional molecular modeling (ONIOM) methods. The circular dichroism results showed that FEN changes the conformation of B-DNA and caused some changes to C-DNA form. The FT-IR results confirmed a partial intercalation between FEN and edges of all base pairs. The competitive fluorescence, using methylene blue as fluorescence probe, in the presence of increasing amounts of FEN, revealed that FEN is able to release the non-intercalated methylene blue from the DNA. The weak chemical shift and peak broadening of (1)H NMR spectrum of FEN in the presence of DNA confirmed a non-intercalation mode. The (31)P NMR showed that FEN interacts more with DNA via its -NO2 moiety. The ONIOM, based on the hybridization of QM/MM (DFT, 6.31++G (d,p)/UFF) methodology, was also performed by Gaussian 2003 package. The results revealed that the interaction is base sequence dependent, and FEN interacts more with AT base sequences.

Binding studies of the antidiabetic drug, metformin to calf thymus DNA using multispectroscopic methods

Interaction between antidiabetic drug, Metformin and calf thymus DNA (CT-DNA) in (50mM Tris-HCl) buffer were studied by UV-Visible absorption, fluorescence, CD spectroscopy and viscosity measurements. In fluorimetric studies, the enthalpy and entropy of the reaction between the drug and CT-DNA showed that the reaction is exothermic (ΔH=-35.4522 kJ mol(-1); ΔS=-49.9523 J mol(-1)K(-1)). The competitive binding studies showed that the drug could release Hoechst 33258 completely. The complex showed absorption hyperchromism in its UV-Vis spectrum with DNA. The calculated binding constant, K(b), obtained from UV-Vis absorption studies was 8.3×10(4)M(-1). Moreover, the changes in the CD spectra in the presence of the drug show stabilization of the right-handed B form of CT-DNA. Finally, viscosity measurements revealed that the binding of the complex with CT-DNA could be surface binding, mainly due to groove binding.

Spectroscopic studies on the binding of holmium-1,10-phenanthroline complex with DNA

Fluorescence and absorption spectroscopy, circular dichroism (CD) as well as viscosity experiment have been used to characterize the DNA binding of [Ho(Phen)(2)Cl(3)]·H(2)O, where phen stand for 1,10-phanathroline. This complex exhibits the marked decrease in the emission intensity and some hypochromism in UV-Vis spectrum in the presence of DNA. For characterization of the binding mode between the Ho(III) complex and DNA various procedures such as: absorption and emission titration and EB quenching experiments, viscosity measurements, CD study, iodide quenching assay, salt effect and thermodynamical investigation are used. The intrinsic binding constant of [Ho(Phen)(2)Cl(3)]·H(2)O with DNA is calculated by UV-Vis and florescence spectroscopy. The value of binding constants in 296, 299 and 303 are 1.99 ± 0.07 × 10(4), 1.07 ± 0.09 × 10(4) and 0.84 ± 0.06 × 10(4), respectively. The thermodynamic studies show that the reaction is entropically driven. The above-mentioned physical measurements indicate that the Ho(III) complex binds to fish salmon DNA, presumably via groove binding mode.

Spectrophotometric and thermodynamic studies of the interactions of 4-carboxyl-2,6-dinitrophenylazohydroxynaphthalenes with bovine serum albumin

The intermolecular interaction occurring between bovine serum albumin and 4-carboxyl-2,6-dinitrophenylazohydroxynaphthalene in aqueous media has been studied spectrophotometrically at different temperatures including body temperature. Evidence for the formation of new molecular complexes was established by hypsochromic and hypochromic shifts of the spectra of dye-BSA complexes compared to the spectra of unbound dyes. One congener (AZ-02) gave a minor peak characteristic of charge-transfer complexation. The binding constants of the four monoazo dyes were investigated and found to vary according to the dye structure and temperature of investigation. AZ-01 and -04 combined with BSA at approximately 1:1 mol ratio while the other two congeners with additional proton donors gave greater than this mole ratio. Thermodynamic considerations established that the dyes utilized the various forms of binding modes; hydrogen bonding, hydrophobic bonding, van der Waals and AZ-03 was particularly involved in electrostatic interactions giving positive entropy change for a small enthalpy change. The observed properties were correlated with the genotoxicity potentials of the monoazo dyes. The results obtained should prove beneficial in designing other molecules in this category of chemical class.

Multispectroscopic studies of the interaction of calf thymus DNA with the anti-viral drug, valacyclovir

The present study investigated the binding interaction between an antiviral drug, valacyclovir and calf thymus DNA (CT-DNA) using emission, absorption, circular dichroism, viscosity and DNA melting studies. In fluorimetric studies, thermodynamic enhancement constant (K(D)) and bimolecular enhancement constant (K(B)) were calculated at different temperatures and demonstrated that fluorescence enhancement is not initiated by a dynamic process, but instead by a static process that involves complex DNA formation in the ground state. Further, the enthalpy and entropy of the reaction between the drug and CT-DNA showed that the reaction is exothermic and enthalpy-favored. In addition, detectable changes in the circular dichroism spectrum of CT-DNA in the presence of valacyclovir indicated conformational changes in the DNA double helix following interaction with the drug. All these results prove that this antiviral drug interacts with CT-DNA via an intercalative mode of binding.