New advances in the study on the interaction of [Cr(phen)2(dppz)]3+ complex with biological models; association to transporting proteins

A mononuclear diketone-based oxido-vanadium(iv) complex: structure, DNA and BSA binding, molecular docking and anticancer activities against MCF-7, HPG-2, and HT-29 cell lines

A mononuclear oxido-vanadium(iv) complex, [VO(L)₂], has been synthesized and its interactions with DNA and BSA have been investigated experimentally and theoretically.

Binding of [Cr(phen)3](3+) to transferrin at extracellular and endosomal pHs: potential application in photodynamic therapy

BACKGROUND

Transferrin is an iron-binding blood plasma glycoprotein that controls the level of free iron in biological fluids. This protein has been deeply studied in the past few years because of its potential use as a strategy of drug targeting to tumor tissues. Chromium complex, [Cr(phen)3](3+) (phen=1,10-phenanthroline), has been proposed as photosensitizers for photodynamic therapy (PDT). Thus, we analyzed the binding of chromium complex, [Cr(phen)3](3+), to transferrin for a potential delivery of this diimine complex to tumor cells for PDT.

METHODS

The interaction between [Cr(phen)3](3+) and holotransferrin (holoTf) was studied by fluorescence quenching technique, circular dichroism (CD) and ultraviolet (UV)-visible spectroscopy.

RESULTS

[Cr(phen)3](3+) binds strongly to holoTf with a binding constant around 10(5)M(-1), that depends on the pH. The thermodynamic parameters indicated that hydrophobic interactions played a major role in the binding processes. The CD studies showed that there are no conformational changes in the secondary and tertiary structures of the protein.

CONCLUSIONS

These results suggest that the binding process would occur in a site different from the specific iron binding sites of the protein and would be the same in both protein states. As secondary and tertiary structures of transferrin do not show remarkable changes, we propose that the TfR could recognize the holoTf despite having a chromium complex associated.

GENERAL SIGNIFICANCE

Understanding the interaction between [Cr(phen)3](3+) with transferrin is relevant because this protein could be a delivery agent of Cr(III) complex to tumor cells. This can allow us to understand further the role of Cr(III) complex as sensitizer in PDT.

DNA- and BSA-binding studies and anticancer activity against human breast cancer cells (MCF-7) of the zinc(II) complex coordinated by 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine

Binding studies of a mononuclear zinc(II) complex, [Zn(dppt)2Cl2] (dppt is 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine), with DNA and bovine serum albumin (BSA) have been investigated under physiological conditions. The binding properties of the complex with fish sperm DNA (FS-DNA) have been investigated by UV-Vis absorption, thermal denaturation, competitive DNA-binding studies with ethidium bromide (EB) by fluorescence, and gel electrophoresis techniques. The competitive study with (EB) shows that the complex can displace EB from the DNA-EB system and compete for the DNA-binding sites with EB, which is usually characteristic of the intercalative interaction of compounds with DNA. The value of the fluorescence quenching constant (Ksv) was obtained as 3.1×10(4)M(-1), indicating that this complex shows a high quenching efficiency and a significant degree of binding to DNA. Moreover, the intercalative binding mode has also been verified by the results of UV-Vis absorption, thermal denaturation and gel electrophoresis. The value of Kb at room temperature was calculated to be 1.97×10(5)M(-1), indicating that the complex possesses strong tendency to bind with DNA. This value is very greater than to the values obtained for other zinc(II) complexes. The interaction of the complex with BSA has been studied by UV-Vis absorption, fluorescence and circular dichroism (CD) spectroscopic techniques. The results indicate that the complex has a quite strong ability to quench the fluorescence of BSA and the binding reaction is mainly a static quenching process. The quenching constants (KSV), the binding constants (Kb), the number of binding sites at different temperatures, the binding distance between BSA and the complex (r), and the thermodynamic parameters (ΔH(o), ΔS(o) and ΔG(o)) between BSA and the complex were calculated. The complex exhibits good binding propensity to BSA showing relatively high binding constant values. The positive ΔH(o) and ΔS(o) values indicate that the hydrophobic interaction is main force in the binding of the complex to BSA. Moreover, to evaluate the anticancer properties, the cytotoxicity of the complex has been tested against the human breast adenocarcinoma (MCF-7) cell lines using the MTT assay. The results indicate that the parent complex displays cytotoxicity against human breast cancer cell lines (MCF-7) with an IC50 value of 10.44μM. It is remarkable that the complex can introduce as a potential anticancer drug.

Fast synthesis of a tris(N,N-diimine)chromium(iii) complex by a microwave-assisted approach

This article describes a quick, easy and eco-friendly procedure to synthesize [Cr(biim)₃](NO₃)₃ by employing microwave irradiation.

DNA/BSA binding, DNA cleavage and electrochemical properties of new multidentate copper(ii) complexes

A new series of multidentate copper(ii) complexes [Cu(L¹⁻⁵)](ClO₄) (1–5) were synthesized and characterized for their DNA/BSA binding, DNA cleavage, cytotoxic properties and antimicrobial activities.

Synthesis, crystal structure and interaction of L-valine Schiff base divanadium(V) complex containing a V2O3 core with DNA and BSA

A divanadium(V) complex, [V2O3(o-van-val)2] (o-van-val=Schiff base derived from o-vanillin and L-valine), has been synthesized and structurally characterized. The crystal structure shows that both of the vanadium centers in the complex have a distorted octahedral coordination environment composed of tridentate Schiff base ligand. A V2O3 core in molecular structure adopts intermediate between cis and trans configuration with the O1V1⋯V1AO1A torsion angle 115.22 (28)° and the V1⋯V1A distance 3.455Å. The binding properties of the complex with calf thymus DNA (CT-DNA) have been investigated by UV-vis absorption, fluorescence, CD spectra and viscosity measurement. The results indicate that the complex binds to CT-DNA in non-classical intercalative mode. Meanwhile, the interaction of the complex with bovine serum albumin (BSA) has been studied by UV-vis absorption, fluorescence and CD spectra. Results indicated that the complex can markedly quench the intrinsic fluorescence of BSA via a static quenching process, and cause its conformational change. The calculated apparent binding constant Kb was 1.05×10(6)M(-1) and the binding site number n was 1.18.

BSA binding and antimicrobial studies of branched polyethyleneimine-copper(II)bipyridine/phenanthroline complexes

The interaction of two water soluble branched polyethyleneimine-copper(II) complexes containing bipyridine/phenanthroline with bovine serum albumin (BSA) was studied by, UV-Visible absorption, fluorescence, lifetime measurements and circular dichroism spectroscopic techniques. The polymer-copper(II) complexes strongly quench the intrinsic fluorescence of BSA is the static quenching mechanism through hydrogen bonds and van der Waal's attraction. The distance r, between the BSA and the complexes seems to be less than 2 nm indicating that the energy transfer between the donor and acceptor occurs with high probability. Synchronous fluorescence studies indicate the binding of polymer-copper(II) complexes with BSA mostly changes the polarity around tryptophan residues rather than tyrosine residues. The circular dichroism studies indicate that the binding has induced considerable amount of conformational changes in the protein. The complexes also show some antibacterial and antifungal properties.

Spectral characterization of the binding and conformational changes of serum albumins upon interaction with an anticancer drug, anastrozole

The present study employed different optical spectroscopic techniques viz., fluorescence, FTIR, circular dichroism (CD) and UV-vis absorption spectroscopy to investigate the mechanism of interaction of an anticancer drug, anastrozole (AZ) with transport proteins viz., bovine serum albumin (BSA) and human serum albumin (HSA). The drug, AZ quenched the intrinsic fluorescence of protein and the analysis of results revealed the presence of dynamic quenching mechanism. The binding characteristics of drug-protein were computed. The thermodynamic parameters, enthalpy change (ΔH°) and entropy change (ΔS°) were calculated to be +92.99 kJ/mol and +159.18 J/mol/K for AZ-BSA and, +99.43 kJ/mol and +159.19 J/mol/K for AZ-HSA, respectively. These results indicated that the hydrophobic forces stabilized the interaction between the drug and protein. CD, FTIR, absorption, synchronous and 3D fluorescence results indicated that the binding of AZ to protein induced structural perturbation in both serum albumins. The distance, r between the drug and protein was calculated based on the theory of Förster's resonance energy transfer and found to be 5.9 and 6.24 nm, respectively for AZ-BSA and AZ-HSA.