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.

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.

Effect of Cu(II) compound containing dipicolinic acid on DNA damage: a study of antiproliferative activity and DNA interaction properties by spectroscopic, molecular docking and molecular dynamics approaches.

A polymeric compound formulized as [Cu(µ-dipic)2{Na2(µ-H2O)4]n.2nH2O (I), where dipic is 2,6-pyridine dicarboxylic acid (dipicolinic acid, H2dipic), was synthesized by sonochemical irradiation. The initial in-vitro cytotoxic activity of this complex compared with renowned anticancer drugs like cisplatin, versus HCT116 colon cell lines, shows promising results. This study investigated the interaction mode between compound (I) and calf-thymus DNA utilizing a range of analytical techniques including spectrophotometry, fluorimetry, partition coefficient analysis, viscometry, gel electrophoresis and molecular docking technique. The results obtained from experimental methods reveal complex (I) could bind to CT-DNA via hydrogen bonding and van der Waals forces and the theoretical methods support it. Also, complex (I) indicates nuclease activity in the attendance of H2O2 and can act as an artificial nuclease to cleave DNA with high efficiency.Communicated by Ramaswamy H. Sarma.

Synthesis, crystal structure, cytotoxicity, in-detail experimental and computational CT-DNA interaction studies of 2-picolinate Pd(II) and Pt(II) complexes.

A new Pd(II) complex of formula [Pd(en)(2-pyc)]+ (where, en is ethylenediamine and 2-pyc is 2-pyridinecarboxylate anion) and its reported Pt(II) analogue, i.e. [Pt(en)(2-pyc)]+ have been made by an improved synthetic procedure, yielding above 80%. They have been characterized by FT-IR, UV-Vis, 1H NMR, 13C NMR, conductivity and elemental analysis. Single crystal structural determination of [Pt(en)(2-pyc)]+ displayed that the Pt(II) cation in this complex coordinated by 2-pyc and en each as five member chelate resulting in slightly distorted square-planar array. The time-dependent spectroscopic analysis of these compounds in aqueous medium demonstrated their structural stabilities. The cytotoxic activities of Pd(II) and Pt(II) complexes, free 2-pyc and carboplatin (as standard drug) were assayed in-vitro against the HCT-116 and MCF-7 as cancerous and MCF 10 A and CCD-841 as normal cell lines. They showed the IC50 order of: carboplatin > 2-pyc > Pt(II) > Pd(II) and lower activities against non-cancerous cells. CT-DNA binding of the Pd(II), Pt(II) and 2-pyc free ligand were explored individually. In this relation, UV-Vis and fluorescence titrations disclosed quenching of CT-DNA absorption and emissions by the compounds via dynamic mechanism and formation of H-bonds and van der Waals forces between them. The interaction was further validated and verified by viscosity measurements and gel electrophoresis. Partition coefficient determination showed that all three compounds have more lipophilicity than cisplatin. Furthermore, docking analysis and molecular dynamics simulation were done to evaluate the nature of interaction between aforementioned compounds and CT-DNA. The finding results demonstrated that these agents interact with CT-DNA via groove binding and were in agreement with experimental results.Communicated by Ramaswamy H. Sarma.

Probing the combination of erlotinib hydrochloride, an anticancer drug, and human serum albumin: Spectroscopic, molecular docking, and molecular dynamic analyses.

Human serum albumin (HSA) is a globular and monomeric protein in plasma that transports many drugs and compounds. Binding of some drugs to HSA can lead to changes in its stability and biological function. We investigated the binding interactions between erlotinib hydrochloride (Erlo) and HSA. Erlo is used to treat lung, pancreatic, and some other cancers. Experimental data showed that the fluorescence emission of the protein was quenched by Erlo using a static quenching mechanism. The calculation of the binding constant, Kb (1.57 × 105 M-1 at 300 K), confirmed the existence of a moderate binding interaction between Erlo and HSA. The interaction was enthalpy driven, spontaneous, and exothermic. The calculated thermodynamic parameters in agreement with simulation and molecular docking data showed that van der Waals and hydrogen bond forces played an important role in the interaction process. Molecular docking results indicated that Erlo has more affinity to bind to subdomain IIA (site I) of HSA. Molecular dynamics simulation analysis showed that the protein is stable in the presence of Erlo under simulation conditions.

Schiff base compounds as artificial metalloenzymes.

Much research has been done on traditional homogeneous metal catalysts and enzymatic catalysts, but recently a new class of hybrid catalysts called synthetic (artificial) metalloenzymes has been considered by researchers. Metalloenzymes as hybrid catalysts (host-guest systems) have been shown that combine the properties of a homogeneous and also enzymatic catalyst. The hybrid catalyst will have added value such as enantioselectivity or chemo-selectivity. This review focuses on Schiff base complexes that either act as homogeneous artificial enzymes or contribute to the structure of a host in the preparation of hybrid metalloenzymes. Because this approach can virtually be applied to any bio- or synthetic host or guest coordination complex, the details of hybrid catalysts seem important for advance in catalysis.

The role of folic acid in inducing of apoptosis by zinc(II) complex in ovary and cervix cancer cells.

Herein, the synthesis, structure, binding affinity, cytotoxicity, and apoptotic properties of the new Zn(II) complex composed of folic acid and bipyridine ligands are reported. Because folic acid has the ability to target cancer cells directly, so it can play a role in targeted drug delivery of the complex and be useful to distinguish normal cells from cancerous. After characterization of Zinc complex utilizing FTIR, EA, and NMR, the results of MTT assay were shown that viability levels of two FR-positive cell lines (HeLa and Ovcar-3) are dependent on time and concentration of [Zn(bpy)FA], whereas, did not show a significant effect on FR-negative cell lines (A549). Also, Real-time PCR revealed that the presence of FA can influence the expression of apoptosis in cervical carcinoma HeLa cells while cisplatin alone doesn't have the ability to trigger apoptosis. Furthermore, the experimental results were evaluated using pharmacophore modeling and molecular docking analysis. Finally, the stability of the Zn(II) complex was surveyed using quantum mechanical studies.

Structural and functional changes of catalase through interaction with Erlotinib hydrochloride. Use of Chou's 5-steps rule to study mechanisms.

Erlotinib hydrochloride (Erlo) is used in the treatment of non-small cell lung cancer, pancreatic cancer and other types of cancer. Interaction of small molecules with bio-macromolecules can lead to changes in the structure and function of them which is one of the possible side effects of the drugs. In this study, the interaction of Erlo with bovine liver catalase (BLC) using spectroscopic and computational methods is presented in detail. The enzymatic function of BLC decreased to 58.7% when the concentration of the Erlo was 0.5 × 10-7 M. Fluorescence results revealed that the combination of BLC with Erlo undergoes static quenching mechanism (Kb = 1.15 × 104 M-1 at 300 K). The interaction process was spontaneous, exothermic and enthalpy-driven and Van der Waals and hydrogen bonds forces played major roles in the this process. UV-Vis, CD, 3D, and synchronous fluorescence measurements indicated the changes in the microenvironment residues and α-helix contents of BLC in the presence of Erlo. Docking and molecular dynamics presented a stable binding configuration and their results were perfectly consistent with the spectroscopic results. Theoretical calculations and experimental analysis help to fully understand of drug interaction with important biological molecules such as enzymes.

A mechanistic explanation of two novel Zn(II) dithiocarbamate complexes with ß-lactoglobulin.

The synthesis, characterization, antioxidant activity and ß-LG interaction of two Zn(II) complexes formulated as [(N-N)Zn(µ-pr-dtc)Zn(N-N)](NO3)2] (where pr-dtc is propylenbisdithiocarbamate, N-N are 2,2'-bipyridine for complex a, and 1,10 phenanthroline for complex b) were reported. The in vitro antioxidant activity of the Zn complexes was evaluated against 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH). Both complexes presented moderate antioxidant activity (IC50 = 231.0 ± 5.7 mg L-1 for complex a and 250.0 ± 6.1 mg L-1 for complex b). Fluorescence studies showed that the intrinsic fluorescence of ß-LG was statically quenched by the prepared complexes mainly through Van der Waals interaction and hydrogen bond. The fluorescence results showed that the above complexes could bind with ß-LG with a relatively strong affinity (complex a:Kb(27 °C) = 0.16 × 104 M-1, Kb(37 °C) = 0.06 × 104 M-1, complex b:Kb(27 °C) = 1.94 × 104 M-1, Kb(37 °C) = 0.11 × 104 M-1). The secondary structure of ß-LG was changed in the presence of these Zn complexes and the decrease in α-helix (0.41% and 0.55% for complex a and complex b, respectively) and ß-sheet (1.19% and 1.44% for complex a and complex b, respectively) contents confirmed the protein instability during the interaction. Molecular dynamics simulation was used during the preparation of the protein receptor before docking to find the best fit of the complexes to ß-LG. Some details about molecular docking simulations describe Van der Waals interactions and hydrogen bonding, and this is in agreement with the thermodynamics data derived from fluorescence spectroscopy experiment.Communicated by Ramaswamy H. Sarma.

Improving the adsorption potential of chitosan for heavy metal ions using aromatic ring-rich derivatives.

This study describes the simple preparation process of modified chitosan (CS) that can effectively adsorb lead ion in the aqueous medium. To design this adsorbent with high binding sites, the Schiff base ligand with three aromatic rings, 3,3-diphenylpropylimine methyl benzaldehyde (PPIMB), is synthesized. The PPIMB forms several new binding sites in modified CS by making a new imine bond with free NH2 in CS structure. The structural and physicochemical characteristics of the magnetically modified chitosan (MCS-PPIMB) are evaluated by FTIR, XRD, SEM, EDX, DLS, VSM, and TG techniques. The effect of some factors, such as pH, collision time, adsorbent dosage, and initial concentration of Pb(II), is investigated on the adsorption capacity of the adsorbent. The adsorption capacity of MCS-PPIMB against Pb(II) is obtained 230.48 mg/g. The adsorption behavior of MCS-PPIMB is fitted efficiently by the Langmuir isotherm model. The fluorometric studies show that the adsorbent has a sharp emission peak at 698 nm, and Pb(II) ion can quench the fluorescence emission of MCS-PPIMB at low concentration. The theoretical studies confirm the strong binding energy of the Pb atom with aromatic rings and imine groups of the MCS-PPIMB.

Catalytic activity and structural changes of catalase in the presence of Levothyroxine and Isoxsuprine hydrochloride.

Two drugs that pregnant women (with hypothyroidism) may use during pregnancy include Isoxsuprine hydrochloride (ISO) and levothyroxine (LEV); ISO to reduce uterine contractions and LEV for the treatment of hypothyroidism. In the current work, we explored the mechanism of binding affinity between the above drugs and antioxidant enzyme Bovine Liver Catalase (BLC). The experimental results confirmed that both drugs could bind with BLC to form drug-BLC complexes but LEV showed a higher binding affinity toward enzyme. The binding constants of LEV-and ISO-BLC were 0.42 × 105 and 0.13 × 104 M-1 at 310 K, respectively. LEV enhanced the catalase activity but the enzymatic activity of BLC reduced gradually in the presence of ISO. Both drugs were able to induce conformational changes in the BLC structure. The results of the molecular docking investigations confirmed the experimental data and showed that the main binding forces in the LEV-BLC and ISO-BLC systems were hydrogen bond and hydrophobic force. The best binding site of both drugs on BLC is located at a cavity among the wrapping domain, N-Terminal arm, and ß-barrel.

Preparation, characterization and comparison of biological potency in two new Zn(II) and Pd(II) complexes of butanedione monoxime derivatives.

A novel Schiff base ligand (2-iminothiophenol-2,3-butanedione monoxime, ITBM) and its complexes with Pd(II) and Zn(II) metal ions ([M(ITBM)2]Cl2) were synthesized and characterized in the present study. The formulated complexes were evaluated for in vitro antioxidant activity as radical scavengers against 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH•). According to the results, antioxidant activity of Pd complex (IC50=36 mg L-1) was more effective than that of Zn(II) complex (IC50=72 mg L-1). Biophysical techniques along with computational modeling were employed to examine the binding of these complexes with human serum albumin (HSA) as the model protein. The trial findings revealed an interaction between Schiff base complexes and HSA with a modest binding affinity [Kb=6.31(±0.11)×104 M-1 for Zn(II) complex and 0.71(±0.05)×104 M-1 for Pd(II) complex at 310 K]. An intense fluorescence quenching of protein through a static quenching mechanism was occurred due to the binding of both complexes to HSA. Hydrogen bonds and van der Waals forces in both examined systems were the main stabilizing forces in the development of drug-protein complex. Based on far-UV-CD observations, the content of α-helical structure in the protein was reduced through induction by both complexes. Analysis of protein-ligand docking demonstrated binding of the two Schiff base complexes to residues placed in the IIA subdomain of HSA. In addition, Zn complex with HSA showed a stronger binding ability than that of Pd complex.Communicated by Ramaswamy H. Sarma.

Synthesis and characterization of an adsorptive Schiff base-chitosan nanocomposite for removal of Pb(II) ion from aqueous media.

A new magnetic chitosan-(2-iminothiophenol methyl)benzaldehyde Schiff base-based adsorbent (MCS-ITMB) was synthesized to be effective adsorbent for adsorption of Pb+2 from aqueous solutions. The adsorbent was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), vibrating sample magnetometer (VSM) and X-ray Diffraction (XRD). Batch adsorption experiments were done under various conditions, such as adsorbent dose, pH, and contact time. The equilibrium data were fitted to Langmuir and Freundlich isotherm models. The maximum monolayer capacity obtained from the Langmuir isotherm was 134.10 mg/g. The MCS-ITMB was found to be regenerated effectively up to five efficient cycles of adsorption/desorption processes. The mechanism for Pb+2 adsorption onto MCS-ITMB involved the interactions of N, O and S atoms and also aromatic rings with heavy metal followed by their adsorption on the MCS-ITMB.

Anti-cancer study and whey protein complexation of new lanthanum(III) complex with the aim of achieving bioactive anticancer metal-based drugs.

In this study, a new lanthanum (III)-amino acid complex utilizing cysteine has been synthesized and characterized. The anticancer activities of the prepared La(III) complex against MCF-7 cell lines were studied. Results of MTT assay showed that at all three incubation times, the cytotoxic effect of prepared La(III) complex on MCF-7 breast cancer cell lines displays a time- and dose-dependent inhibitory effects. The interactions of the La(III) complex with two whey proteins (bovine serum albumin, BSA, and Bovine ß-lactoglobulin, ßLG) have been explored by using spectroscopic and molecular dicking methods. The obtained results indicated that La(III) complex strongly quenched the fluorescence of two carrier proteins in static quenching mode and also, BSA hah stronger binding affinity toward studied complex than ßLG whit binding constant values of KBSA-La Complex ∼ 0.11 × 104 M-1 and KßLG-La Complex ∼ 0.63 × 103 M-1 at 300 K. The thermodynamic parameters revealed the contribution of hydrogen bond and Vander Waals interactions in both systems. The distances of the La(III) complex whit whey proteins were calculated using Förster energy transfer theory and proved existence of the energy transfer between two proteins and prepared La(III) complex with a high probability. FT-IR and UV-Vis absorption measurements indicated that the binding of the La(III) to BSA and ßLG may induce conformational and micro-environmental changes of the proteins. The docking results indicate that the La(III) complex bind to residues located in the site II of BSA and second site of ßLG. Communicated by Ramaswamy H. Sarma.

Magnetic chitosan-(d-glucosimine methyl)benzaldehyde Schiff base for Pb+2 ion removal. Experimental and theoretical methods.

Magnetic chitosan nanocomposite (magnetic chitosan-(d-glucosimine methyl)benzaldehyde, MCS-Sch) on the basis of Schiff base-functionalized magnetite nanoparticles was synthesized. The prepared MCS-Sch was characterized by 1H NMR, FT-IR, XRD, SEM, EDX, DLS, and VSM analysis. The MCS-Sch can be removed from aqueous solution with the help of an external magnet. The efficiency of the synthesized nanocomposite was studied for the Pb(II) ion removal from aqueous solutions. The effects of pH, contact time and initial concentration on the adsorption process were evaluated. Based on the Langmuir isotherm model, the maximum adsorption capacity of MCS-Sch obtained 121.95 mg/g for Pb(II) ion. The binding of prepared nanocomposite and Pb(II) ion was reversible, so the MCS-Sch can maintain its ability for metal ion removal from aqueous solutions. Finally, theoretical calculations showed that the presence of aromatic ring at the prepared magnetic chitosan nanocomposite, MC-Sch, is a favorable factor in Pb(II) ion absorption.

Binding interaction of isoxsuprine hydrochloride and levothyroxine to milk ß-lactoglobulin; from the perspective of comparison.

Isoxsuprine hydrochloride (ISO) and levothyroxine (LEV) are medicines which can be utilized alone or simultaneously by pregnant women. The purpose of this work is to investigate the separate and simultaneous interaction of ISO and LEV with ß-LG. The results showed that both drugs can bind to ß-LG; the static quenching was suggested for fluorescence quenching mechanism of ß-LG.The values of binding constants (Kß-LG-ISO = 2.69 × 104 M-1, Kß-LG-LEV = 0.54 × 103 M-1 and Kß-LG-ISO-LEV = 2.18 × 103 M-1 at 310 K) suggested that ISO has stronger binding affinity toward ß-LG than LEV and affinity of ß-LG to LEV is increased in the presence of ISO while the presence of LEV has no significant effect on the affinity of protein to ISO. Thermodynamic parameters showed that the binding of LEV to ß-LG are hydrogen bonding and Van der Waals forces but the formation of ß-LG-ISO is hydrophobic associations. The results of FT-IR and UV-visible measurements indicated that the binding of both drugs to ß-LG may induce conformational changes of protein. In silico molecular docking analyses confirmed that ISO and LEV binds to residues located at site I and site II of ß-LG, respectively.

Synthesis, characterization, in silico ADMET prediction, and protein binding analysis of a novel zinc(II) Schiff-base complex: Application of multi-spectroscopic and computational techniques.

By reaction of 1,2-diaminocyclohexane with the 2,3-butanedione monoxime in the presence of ZnCl2, a new Schiff base complex was obtained. This complex was characterized by elemental analyses, FT-IR, 1H NMR, UV-Vis, and conductivity measurements. The reactivity of this complex to human serum albumin (HSA) under simulative physiological conditions was studied by spectroscopic and molecular docking analysis. Experimental results at various temperatures indicated that the intrinsic fluorescence of protein was quenched through a static quenching mechanism. The negative value of enthalpy change and positive value of entropy change indicated that both hydrogen bonding and hydrophobic forces played a major role in the binding of Zn(II) complex to HSA. FT-IR, three-dimensional fluorescence, and UV-Vis absorption results showed that the secondary structure of HSA changed after Zn(II) complex bound to protein. The binding distance was calculated to be 4.96 nm, according to fluorescence resonance energy transfer. Molecular docking results confirmed the spectroscopic results and showed that above complex is embedded into subdomain IIA of protein. All these experimental and computational results clarified that Zn(II) complex could bind with HSA effectively, which could be a useful guideline for efficient Schiff-base drug design.

Biophysical and computational comparison on the binding affinity of three important nutrients to ß-lactoglobulin: folic acid, ascorbic acid and vitamin K3.

Small globular protein, ß-lactoglobulin (ßLG), which has significant affinity toward many drugs, is the most abundant whey protein in milk. In this study, the interaction of ßLG with three important nutrients, ascorbic acid (ASC), folic acid (FOL), and vitamin K3 (VK3) was investigated by spectroscopic methods (UV-visible and fluorescence) along with molecular docking technique. The results of fluorescence measurements showed that studied nutrients strongly quenched ßLG fluorescence in static (FOL and ACS) or static-dynamic combined quenching (VK3) mode. The values of binding constants (KßLG-ASC ~ 4.34 × 104 M-1, KßLG-FOL ~ 1.67 × 104 M-1and KßLG-VK3 ~ 13.49 × 104 M-1 at 310 K) suggested that VK3 and FOL had stronger binding affinity toward ßLG than ASC. Thermodynamic analysis indicated that hydrophobic interactions are the major forces in the stability of FOL-ßLG complex with enthalpy- and entropy-driving mode while, hydrogen bonds and van der Waals interactions play a major role for ßLG-ASC and ßLG-VK3 associations. The results of 3D fluorescence FT-IR and UV-Visible measurements indicated that the binding of above nutrients to ßLG may induce conformational and micro-environmental changes of protein. Also, there is a reciprocal complement between spectroscopic techniques and molecular docking modeling. The docking results indicate that the ASC, FOL, and VK3 bind to residues located in the subdomain B of ßLG. Finally, this report suggests that ßLG could be used as an effective carrier of above nutrients in functional foods.

Investigation on the interaction of newly designed potential antibacterial Zn(II) complexes with CT-DNA and HSA.

Two Zn(II) complexes of formula [Zn(bpy)(Gly)]NO3 (I) and [Zn(phen)(Gly)]NO3 (II) (where bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline and Gly = glycine) were synthesized and characterized by elemental analysis, molar conductance measurements, UV-vis, FT-IR, and 1H NMR spectra. The interaction ability of these complexes with calf thymus DNA was monitored using spectroscopic methods, including UV-vis absorption spectroscopy, ethidium bromide displacement, Fourier transform infrared, and electrophoretic mobility assay. Further, the human serum albumin interactions of complexes I and II were investigated using UV-vis absorption spectroscopy, fluorescence quenching, circular dichroism, and Fourier transform infrared. The results obtained from these analyses indicated that both complexes interact effectively with CT-DNA and HSA. The binding constant (Kb), the Stern-Volmer constant (Ksv), and the number of binding sites (n) at different temperatures were determined for CT-DNA and HSA. Also, the negative ΔH° and ΔS° values showed that both hydrogen bonds and van der Waals forces played major roles in the association of CT-DNA-Zn(II) and HSA-Zn(II) complex formation. The displacement experiments suggested that Zn(II)-complexes primarily bound to Sudlow's site II of HSA. The distance between the donor (HSA) and the acceptor (Zn(II) complexes) was estimated on the basis of the Forster resonance energy transfer (FRET) and the alteration of HSA secondary structure induced by the compounds were confirmed by FT-IR spectroscopy. The complexes follow the binding affinity order of I > II with DNA and II > I with HSA. Finally, Antibacterial activity of complexes I and II have been screened against gram positive and gram negative bacteria.

Binding forces between a novel Schiff base palladium(II) complex and two carrier proteins: human serum albumi and ß-lactoglobulin.

Ligand binding studies on carrier proteins are crucial in determining the pharmacological properties of drug candidates. Here, a new palladium(II) complex was synthesized and characterized. The in vitro binding studies of this complex with two carrier proteins, human serum albumin (HSA), and ß-lactoglobulin (ßLG) were investigated by employing biophysical techniques as well as computational modeling. The experimental results showed that the Pd(II) complex interacted with two carrier proteins with moderate binding affinity (Kb ≈ .5 × 104 M-1 for HSA and .2 × 103 M-1 for ßLG). Binding of Pd(II) complex to HSA and ßLG caused strong fluorescence quenching of both proteins through static quenching mechanism. In two studied systems hydrogen bonds and van der Waals forces were the major stabilizing forces in the drug-protein complex formation. UV-Visible and FT-IR measurements indicated that the binding of above complex to HSA and ßLG may induce conformational and micro-environmental changes of two proteins. Protein-ligand docking analysis confirmed that the Pd(II) complex binds to residues located in the subdomain IIA of HSA and site A of ßLG. All these experimental and computational results suggest that ßLG and HSA might act as carrier protein for Pd(II) complex to deliver it to the target molecules.