Investigation of kinetics and thermodynamics in the interaction process between two pyridine derived Schiff base complexes and catalase

Molecular docking and biological activities of Ni(II), Cu(II) and Co(II) complexes with a new potentially hexadentate polyamine ligand; X-ray crystal structure of the Cu(II) complex

Three new metal complexes have been obtained from the reaction of a new polyamine (L) with Ni(II), Cu(II), and Co(II) ions. The X-ray structural analysis of the Cu(II) complex shows that the copper atom is in a very distorted square pyramidal environment, coordinated by five of the six nitrogen donor atoms of the potentially hexadentate ligand. To evaluate the biological potential of the ligand and the synthesized metal complexes, their binding behavior with DNA was studied by molecular modeling methods. The Molecular docking studies showed that the free ligand and its complexes were bound to the major groove of DNA. The antioxidant activities of the ligand and its metal complexes were also assessed, in vitro, using 2,2-diphenyl-1-picrylhydrazyl. The synthesized compounds were tested for activity against lung carcinoma epithelial cells (A549) using the MTT cell viability assay. A comparative study of the IC50 values indicated that the Cu(II) complex exhibited the highest activity, while the Co(II) and Ni(II) complexes showed more potent antiproliferative activity than the ligand. The antibacterial activities of the synthesized complexes were evaluated using micro-broth dilution and disk diffusion methods. The complexes showed greater antibacterial activity than the free ligand.Communicated by Ramaswamy H. Sarma.

Effect of central metal ion on some pharmacological properties of new Schiff base complexes. Anticancer, antioxidant, kinetic/thermodynamic and computational studies

The biological capacities of Schiff Base complexes such as anti-cancer, anti-microbial and anti-oxidant properties have been widely studied in the scientific community. However, the effect of central metal ion in the occurrence of their biological properties should be paid more attention. With this aim, novel 2-(hydroxyimino)-1-phenylpropylidene)benzohydrazide (HIPB) Schiff base ligand, and C1/palladium(II), C2/platinum(II), and C3/zinc(II) complexes derived from it were synthesized and characterized. Theoretical studies showed that C2 is more reactive and also has a higher pharmacological affinity than C1 and C3. Experimental investigations were done to compare some biological properties of the complexes. The anticancer assay showed that C1-C3 have the ability to inhibit the growth of HCT116 colon cancer cell lines, but C2 shows a relatively better effect than other. Antioxidant studies using •DPPH (2,2-diphenyl-1-picrylhydrazyl) assay presented the following trend: C2 > C1 > C3 > HIPB. Considering the importance of the antioxidant enzyme catalase in removing reactive oxygen species (ROS), the interaction of C1-C3 with Bovine Liver Catalase (BLC) was evaluated. Kinetic studies showed that C1-C3 can inhibit the catalytic performance of BLC by a similar mechanism, i.e. mixed-type inhibition. Among them, C1 was the strongest inhibitor (Activity inhibition% = 82.2). The C1-C3 quenched the BLC fluorescence emission with dynamic quenching mechanism. The binding affinity to BLC was higher for C1 and C2 than C3. The most important forces in the interaction of C1-C3 with BLC were hydrophobic interactions, which was strongly confirmed by molecular docking data. Tracking the structural changes of catalase showed that BLC undergoes structural changes in the presence of C1 more than C2 and C3.

DNA/BSA interaction, anticancer, antimicrobial and catalytic applications of synthesis of nitro substituted pyrimidine-based Schiff base ligand capped nickel nanoparticles

The objective of this research was to create stable nickel nanoparticles using nickel chloride salt and a Schiff base ligand called DPMN. The synthesis process involved a two-step phase transfer procedure. Spectroscopic techniques such as UV-Visible and FT-IR were used to confirm the formation of ligand-stabilized nickel nanoparticles (DPMN-NiNPs). To analyze the size, surface morphology, and quality of DPMN-NiNPs, SEM and TEM techniques were utilized. In vitro studies were performed to investigate the potential anticancer activity of the synthesized compounds against three different cancer cell lines and one normal cell line, and the results were compared to those of cis-platin. The researchers also conducted tests to determine the ability of DPMN-NiNPs to bind to CT-DNA using various techniques such as electronic absorption, fluorescence, viscometric, and cyclic voltammetric. The results showed that the synthesized DPMN-NiNPs exhibited good DNA binding ability, which was further validated by denaturation of DNA using thermal and sonochemical methods. The researchers also investigated the antimicrobial and antioxidant activities of DPMN-NiNPs, which demonstrated better biological activities than DPMN alone. Furthermore, the synthesized nano compounds were found to selectively damage cancer cell lines without harming normal cell lines. Finally, the researchers examined the potential of DPMN-NiNPs as a catalyst in dye degradation by testing its ability to decompose methyl red dye using UV-Visible spectroscopy.Communicated by Ramaswamy H. Sarma.

Experimental and Theoretical Approaches to Monitor the Behavior of Bovine Liver Catalase in Interaction with a Binuclear Bismuth Complex

Here, the antioxidant potency of a binuclear Bi(III) complex {[Bi2(μ-ox)(dipic)2(H2O)2 (taa)2].H2O, where ox2- = oxalato, dipic2- = pyridine 2,6-dicarboxylato, and taa = thiourea} was evaluated using the •DPPH assay. It was demonstrated that the Bi complex exhibited a high ability to inhibit DPPH free radicals. The binding mechanism of the complex with bovine liver catalase (BLC) was also investigated, revealing structural and activity changes in the enzyme in the presence of the complex. The catalase activity in the decomposition of hydrogen peroxide increased in the presence of the Bi complex, reaching 39.8% higher than its initial activity at a concentration of 7.77 × 10-6 M. The complex exhibited a relatively high affinity for BLC, with K b values of 3.98, 0.13, and 0.09 × 105 M-1 at 303, 310, and 317 K, respectively. The mechanisms involved in the interaction were hydrogen bonding and van der Waals interactions, as validated through molecular docking simulations. Synchronous fluorescence showed that tryptophan was more affected by enzyme-complex interactions than tyrosine. In addition, a cell viability test using the MTT method revealed that at its highest concentration, the Bi complex caused a decrease in the number of cells below 50% compared to the control, while cisplatin showed negative effects at all concentrations. These findings suggest that the Bi complex has the potential to be developed as a promising candidate for BLC-related therapeutic target therapy.

Tracking the binding site of anticancer drug fluxoridin with Fe-related proteins to achieve intelligent drug delivery

In cancer cells that need a lot of iron for growth and metastasis, halo-transferrin (TF-containing iron) enters the cell with the help of the transferrin receptor 1 (TFR1) protein. If the anticancer drug can bind to the iron site by interacting with apo-transferrin (iron-free FT), it can enter the cancer cell by the same mechanism. Two iron-related proteins, Bovine liver catalase (BLC) and apo-Transferrin (TF), that are important in cancer patients were selected and their interaction with the anti-cancer drug Floxuridine (FUDR) was investigated. Here, the protective role of FUDR was evaluated by several variables such as drug concentration, interaction time, and temperature-induced degradation of enzyme function. The results showed that the protective effect of the FUDR is greater in high concentrations (in 5 × 10-5 M:1.78 % and 2.59 % after 24 and 48 h). The interaction of the FUDR with both proteins can reduce the intensity of the fluorescence emission by a static mechanism. The binding strength of the FUDR with both proteins was almost similar and with the order of 104 M-1 (Kb = 3.90 ± 0.41 × 104 M-1 for BLC-FUDR and 5.01 ± 0.36 × 104 M-1 for TF-FUDR at 310 K). The thermodynamic calculations (in agreement with the docking results) indicated that FUDR-protein complex formation was exothermic and the main binding forces in the binding process were van der Waals interactions and hydrogen bonds. Both fluorophores tryptophan (Trp) and tyrosine (Tyr) of both proteins had significant roles in fluorescence quenching and the interaction process, the polarity of their microenvironment changed. CD results showed that the secondary structure changes of TF are slightly more than BLC. Molecular docking showed that the binding of the FUDR to TF is very close to the Fe-specific site and is placed in the cavity among the wrapping domain, N-Terminal arm, and β-barrel in BLC.

Comprehending the intermolecular interaction of JAK inhibitor fedratinib with bovine serum albumin (BSA)/human alpha-1-acid glycoprotein (HAG): Multispectral methodologies and molecular simulation

The primary coverage of this paper is to investigate the molecular interaction of JAK2 inhibitor, fedratinib (FED) with BSA/HAG proteins through multispectral approaches and molecular docking as well as MD calculation. Arrival at a conclusion, the endogenous fluorescence of BSA/HAG protein was quenched separately in the form of static and mixed quenching. The FED-BSA and FED-HAG complexes with the stoichiometric ratio of 1:1 were formed in the interaction process. And, The Kb values of these complexes were of 104-105 M-1 and 105-106 M-1, respectively, representing that the FED-HAG complex exhibited a comparatively high affinity compared to the FED-BSA complex. It is confimed that FED inserted into the interface area between subdomain IIA and IIB of BSA (marked as site II') and the bucket-shaped hydrophobic cavity of HAG, respectively, resulting in the slight alteration in the secondary structure of BSA/HAG and the micro-environment round Tyr and Trp residues. The expetimental results also confirmed that van der Waals forces (VDW), hydrogen bonds and hydrophobic interaction played a dominant role in the formation of two stable complexes. The above experimental results were supplemented and verified through molecular docking and MD simulation. Meanwhile, the effects of common ions on affinity were explored. This study could shine a light on evaluating the pharmacological properties of the JAK inhibitor FED, understanding the distribution and operation of the drug in the body, and leading to the development of the creation of novel medication devise.

Effects of two food colorants on catalase and trypsin: Binding evidences from experimental and computational analysis

Recently, growing concern has been paid to the toxicity of additives in food. The present study investigated the interaction of two commonly used food colorants, quinoline yellow (QY) and sunset yellow (SY), with catalase and trypsin under physiological conditions by fluorescence, isothermal titration calorimetry (ITC), ultraviolet-vis absorption, synchronous fluorescence techniques as well as molecular docking. Based on the fluorescence spectra and ITC data, both QY and SY could significantly quench the intrinsic fluorescence of catalase or trypsin spontaneously to form a moderate complex driven by different forces. Additionally, the thermodynamics results demonstrated QY bind more tightly to both catalase and trypsin than SY, suggesting QY poses more of a threat to two enzymes than SY. Furthermore, the binding of two colorants could not only lead to the conformational and microenvironmental alterations of both catalase and trypsin, but also inhibit the activity of two enzymes. This study provides an important reference for understanding the biological transportation of synthetic food colorants in vivo, and enhancing their risk assessment on food safety.

Investigating binding of insecticide buprofezin to DNA by experimental and metadynamics simulation studies

Buprofezin (BUP) is an insecticide which belongs to the thiadiazine structural family and known to damage DNA in mice. Though its toxic effect on human is not known clearly, understanding the mechanism of interaction of BUP with DNA can prove useful when required. Multi-spectroscopic experiments such as UV-Vis, fluorescence, circular dichroism (CD) and ¹H NMR coupled with viscosity measurements, urea effect and voltametric studies were performed to ascertain the mode of binding of BUP with calf thymus DNA (CT-DNA). Analysis of UV-Vis and fluorescence spectra indicated the formation of a complex between BUP and CT-DNA. Other experiments such as competitive binding assays with ethidium bromide (EB) and Hoechst 33258, viscosity measurements, effect of urea, CD, voltammetric studies and ¹H NMR spectral analysis suggested that BUP intercalates into the base pairs of CT-DNA. All these results revealed that the binding mode of BUP with CT-DNA should be intercalation and the binding constant is in the order of 10⁴ M^-1. The ΔH^o < 0 and ΔS^o < 0 suggested that H-bonding or van der Waals force was the main binding force between BUP and CT-DNA. The proposed mode of binding of BUP with CT-DNA has been visualized using in silico molecular docking and metadynamics simulation studies, which showed that the phenyl ring of BUP binds to CT-DNA via π-π stacking interaction in addition to H-bond formation.Communicated by Ramaswamy H. Sarma.