The interactions between Reactive Black 5 and human serum albumin: combined spectroscopic and molecular dynamics simulation approaches

Azo dyes are made in significant amounts annually and released into the environment after being employed in the industry. There are some reports about the toxic effects of these dyes on several organisms. Thus, the textile dye Reactive Black 5 (RB5) has been examined for its cytotoxic effects on the human serum albumin (HSA) structure. Molecular interaction between RB5 and HSA indicated the combination of docking methods, molecular dynamic simulation, and multi-spectroscopic approaches. HSA's intrinsic fluorescence was well quenched with enhancing RB5 level, confirming complex formation. Molecular dynamics (MD) simulation was done to study the cytotoxic effects of RB5 and HSA conformation. Molecular modeling revealed that the RB5-HSA complex was stabilized by hydrogen bonds and van der Waals interactions. The results of molecular docking revealed that the binding energy of RB5 to HSA was - 27.94 kJ/mol. The change in secondary structure causes the annihilation of hydrogen bonding networks and the reduction of biological activity. This research can indicate a suitable molecular modeling interaction of RB5 and HAS and broaden our knowledge for azo dye toxicity under natural conditions.

Synthesis, characterization, cytotoxicity and DNA/BSA binding of two amino acid palladium(II) complexes derived from alanine and valine

Two novel palladium(II)-amino acid complexes, [Pd(Ala)2]·H2O (PA) and [Pd(Val)2].H2O (PV) (Ala = alanine; Val = valine) were synthesized and characterized through FTIR, UV/Vis, 1H-NMR spectroscopies, CHN analysis, X-ray crystallography and molar conductivity measurement. Furthermore, cytotoxicity of Pd(II) complexes against human leukemia cancer cell line, MOLT4 showed promising cancer cell death (CC50 = 0.71 ± 0.046 µM for PA; CC50 = 0.85 ± 0.063 µM for PV) that were less than cisplatin (1.59 ± 0.25 µM). Moreover, the interaction of both the complexes with DNA and BSA was studied using UV-Vis absorption and emission spectroscopic techniques that demonstrated the bindings occurred via van der Waals forces and hydrogen bond. Furthermore, the fluorescence titration showed that static quenching mechanism plays predominate role in binding process. All results showed that both complexes have more binding tendency to DNA in compared to BSA that can be a significant achievement for further medical purposes as a potential antitumor candidate. Finally, molecular docking simulation was performed for PA and PV complexes with DNA and BSA and demonstrated both complexes bind to the groove of DNA mainly by hydrogen bond and interact with site I of BSA via hydrogen bond as well.

Insight into the binding of glycerol with myoglobin: Spectroscopic and MD simulation approach

Stability of proteins plays a significant role not only in their biological function but also in medical science and protein engineering. Since proteins are only stable in special conditions, maintaining their stability and function in biological and biotechnological applications may pose serious challenges. Osmolytes provide a general method of shielding proteins from the unfolding and aggregation caused by extreme stress on the environment. In such studies, the researchers used spectroscopic and simulation approaches to study the alterations of the myoglobin structure and stability in glycerol presence. Experimental results showed a stability improvement of the complex myoglobin-glycerol. After the addition of glycerol resulting in the initiation of hydrogen bonds and higher levels of hydrophobicity, the increase of the T_m was observed. The static mode quenching observed in this study. Van der Waals forces and hydrogen bindings had a decisive and significant role concerning the stability of protein which was consistent with the modeling results. Molecular dynamics simulation showed that the glycerol presence could enhance myoglobin stability. The consistency between the theoretical studies and experimental findings demonstrates that the method proposed in this study could provide a useful method for protein-ligand complex investigations.

Experimental and theoretical investigations on the interaction of glucose molecules with myoglobin in the aqueous solution using theoretical and experimental methods

Osmolytes are generally well-known for the stabilization of proteins. The stabilizing impact of glucose on the dynamics and structure of myoglobin was probed through molecular simulation' docking and spectroscopic procedures. Using thermal stability examinations, the thermodynamic folding properties, point of melting temp. (T_m), thermodynamic enthalpy change (ΔH°) and thermodynamic entropy change (ΔS°) were determined to find out the depiction of myoglobin folding. Glucose operated as an enhancer relative to myoglobin stabilization. The quenching static model was demonstrated by fluorescence spectroscopy. There was one binding site. According to the spectroscopy analysis, glucose was capable of protecting the native structural conformation of protein as well as preventing from protein unfolding. The fluorescence spectroscopy together with simulation through molecular docking method revealed that definitely hydrogen bonding plus van der Waals forces had major contributions to the stabilization of the myoglobin-glucose complex. Hence, the direct interactions contributed slightly to the stabilization impact whereas indirect interactions resulted from the hydration arise from a molecular mechanism primarily inducing the glucose stabilizing impacts. An elevation occurred in the T_m of the myoglobin-glucose complex because of the greater H-bond creation and limited surface hydrophobic activity. Our findings indicate that glucose was capable of protecting the native conformation of myoglobin, clearly describing that glucose stabilization is preferred to be omitted from myoglobin surface. This is because water is more inclined to provide desirable interacting with myoglobin functional groups as compared to glucose. Also, MD results confirmed that the structural changes of myoglobin is the effect of complex formation with glucose.Communicated by Ramaswamy H. Sarma.

Nonionic but water soluble, [Glycine-Pd-Alanine] and [Glycine-Pd-Valine] complexes. Their synthesis, characterization, antitumor activities and rich DNA/HSA interaction studies

Two novel, neutral and water soluble Pd(II) complexes of formula [Pd(Gly)(Ala)] (1) and [Pd(Gly)(Val)] (2) (Gly, Ala, and Val are anionic forms of glycine, alanine, and valine amino acids, respectively) have been synthesized and characterized by FT-IR, UV-Vis, ¹H-NMR, elemental analysis, and molar conductivity measurement. The data revealed that each amino acid binds to Pd(II) through the nitrogen of -NH₂ and the oxygen of -COO^- groups and acts as a bidentate chelate. These complexes have been assayed against leukemia cells (K₅₆₂) using MTT method. The results indicated that both of the complexes display more cytotoxicity than the well-known anticancer drug, cisplatin. The interaction of the compounds with calf thymus DNA (CT-DNA) and human serum albumin (HSA) were assayed by a series of experimental techniques including electronic absorption, fluorescence, viscometry, gel electrophoresis, and FT-IR. The results indicated that the two complexes have interesting binding propensities toward CT-DNA as well as HSA and the binding affinity of (1) is more than (2). The fluorescence data indicated that both complexes strongly quench the fluorescence of ethidium bromide-DNA system as well as the intrinsic fluorescence of HSA via static quenching procedures. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) calculated from the fluorescence studies showed that hydrogen bonds and van der Waals interactions play a major role in the binding of the complexes to DNA and HSA. We suggest that both of the Pd(II) complexes exhibit the groove binding mode with CT-DNA and interact with the main binding pocket of HSA. Communicated by Ramaswamy H. Sarma.

Biological evaluations of newly-designed Pt(II) and Pd(II) complexes using spectroscopic and molecular docking approaches

To perform biological evaluations of newly-designed Pt(II) and Pd(II) complexes, the present study was conducted with targeted protein human serum albumin (HSA) and HCT116 cell line as model of human colorectal carcinoma. The binding of Pt(II) and Pd(II) complexes to HSA was analyzed using fluorescence spectroscopy and molecular docking. The thermal stability and alterations in the secondary structure of HSA in the presence of Pt(II) and Pd(II) complexes were investigated using the thermal denaturation method and circular dichroism (CD) spectroscopy. The cytotoxicity of the Pt(II) and Pd(II) complexes was studied against the HCT116 cell line using MTT assay. The binding analysis revealed that the fluorescence findings were well in agreement with docking results such that there is only one binding site for each complex on HSA. Binding constants of 8.7 × 10³ M^-1, 2.65 × 10³ M^-1, 0.3 × 10³ M^-1, and 4.4 × 10³ M^-1 were determined for Pd(II) and Pt(II) complexes (I-IV) at temperature of 25 °C, respectively. Also, binding constants of 1.9 × 10³ M^-1, 15.17 × 10³ M^-1, 1.9 × 10³ M^-1, and 13.1 × 10³ M^-1 were determined for Pd(II) and Pt(II) complexes (I-IV) at temperature of 37 °C, respectively. The results of CD and thermal denaturation showed that the molecular structure of HSA affected by interaction with Pt(II) and Pd(II) complexes is stable. Cytotoxicity studies represented the growth suppression effect of the Pt(II) and Pd(II) complexes toward the human colorectal carcinoma cell line. Therefore, the results suggest that the new designed Pt(II) and Pd(II) complexes are well promising candidates for use in cancer treatment, particularly for human colorectal cancer. Communicated by Ramaswamy H. Sarma.

Design, synthesis, characterization, cytotoxicity, molecular docking and analysis of binding interactions of novel acetylacetonatopalladium(ii) alanine and valine complexes with CT-DNA and BSA

The neutral, water soluble palladium(ii) amino acid complexes, interact with CT-DNA (groove binding) and BSA (H-binding in main pocket). Molecular docking supports the interactions.

Counteraction of lactose on the thermal stability and activity of α-chymotrypsin: thermodynamic, kinetic and docking studies

Stabilized aqueous solutions of α-chymotrypsin have a therapeutic utility in the treatment of certain forms of asthma, bronchitis, rhinitis, sinusitis, as well as certain dermatological conditions such as leg ulcers and ringworm.

Cytotoxic activity of novel palladium-based compounds on leukemia cell lines

Effective treatment methods for human leukemia are under development, but so far none of them have been found to be completely satisfactory. It was recently reported that palladium complexes have significant anticancer activity as well as lower toxicity compared with some clinically used chemotherapeutics. The anticancer activities of two novel palladium(II) complexes, [Pd(sac)(terpy)](sac)·4H2O and [PdCl(terpy)](sac)·2H2O, were tested against three human leukemia cell lines, Jurkat, MOLT-4, and THP-1, in comparison with cisplatin and adriamycin. The cytotoxic effect of the drugs was determined using the MTT assay. Cell death was assessed using fluorescein isothiocyanate-annexin/propidium iodide staining for flow cytometry. Furthermore, p53 phosphorylation, poly(ADP-ribose) polymerase cleavage, and Bax and Bcl-2 mRNA levels were examined to elucidate the mechanism of cell death induction. Both complexes exhibited a significant dose-dependent antigrowth effect in vitro. The complexes predominately induced apoptosis, but necrosis was also observed. In-vitro results have shown that palladium(II) complexes may be regarded as potential anticancer agents for treating human leukemia. Therefore, further analysis to determine the putative mechanism of action and in-vivo studies on animal models are warranted.

Probing of the interaction between β-lactoglobulin and the anticancer drug oxaliplatin

The potential carrier role of β-lactoglobulin (β-LG) and its interactions with oxaliplatin were studied using various spectroscopic techniques (fluorescence, UV-visible, and circular dichroism (CD)) in an aqueous medium at two temperatures of 25 and 37 °C in combination with a molecular docking study. Fluorescence measurements have shown that the observed quenching is a combination of static and dynamic quenching with a predominant contribution of static mode. The presence of a single binding site located in the internal cavity of the β-barrel of β-LG was confirmed by molecular docking calculations. Thermodynamic data as well as molecular docking indicated that the hydrophobic interactions dominate in the binding site. Results of fluorescence resonance energy transfer (FRET) measurements in combination with docking results imply that resonance energy transfer occurs between β-LG and its ligand oxaliplatin. Additionally, CD results revealed that oxaliplatin binding has no influence on the β-LG structure. The molecular docking results indicate that docking may be an appropriate method for the prediction and confirmation of experimental results. Complementary molecular docking results may be useful for the determination of the binding mechanism of proteins such as β-LG in pharmaceutical and biophysical studies providing new insight in the novel pharmacology and new solutions in the formulation of advanced oral drug delivery systems.

Cytotoxic Effects of Newly Synthesized Palladium(II) Complexes of Diethyldithiocarbamate on Gastrointestinal Cancer Cell Lines

As a part of a drug development program to discover novel therapeutic and more effective palladium (Pd) based anticancer drugs, a series of water-soluble Pd complexes have been synthesized by interaction between [Pd (phen)(H₂O)₂(NO₃)₂] and alkylenebisdithiocarbamate(al-bis-dtc) disodium salts. This study was undertaken to examine the possible cytotoxic effect of three novel complexes (0.125–64 µg/mL) on human gastric carcinoma (AGS), esophageal squamous cell carcinoma (Kyse-30), and hepatocellular carcinoma (HepG2) cell lines. The cytotoxicity was examined using cell proliferation and acridine orange/ethidium bromide (AO/EB) assay. In order to examine the effects of new Pd(II) complexes on cell cycle status, we performed cell cycle analysis. The complexes were found to have completely lethal effects on the cell lines, and the half maximal inhibitory concentration (IC50) values obtained for the cell lines were much lower in comparison with cisplatin. We demonstrated that the three new Pd(II) complexes are able to induce G2/M phase arrest in AGS and HepG2; in addition, the Pd(II) complexes caused an S phase arrest in Kyse-30 cell line. Our results indicate that newly synthesized Pd(II) complexes may provide a novel class of chemopreventive compounds for anticancer therapy.

Spectroscopic and theoretical investigation of oxali-palladium interactions with β-lactoglobulin

The possibility of using a small cheap dairy protein, β-lactoglobulin (β-LG), as a carrier for oxali-palladium for drug delivery was studied. Their binding in an aqueous solution at two temperatures of 25 and 37°C was investigated using spectroscopic techniques in combination with a molecular docking study. Fluorescence intensity changes showed combined static and dynamic quenching during β-LG oxali-palladium binding, with the static mode being predominant in the quenching mechanism. The binding and thermodynamic parameters were determined by analyzing the results of quenching and those of the van't Hoff equation. According to obtained results the binding constants at two temperatures of 25 and 37°C are 3.3×10(9) M(-1) and 18.4×10(6) M(-1) respectively. Fluorescence resonance energy transfer (FRET) showed that the experimental results and the molecular docking results were coherent. An absence change of β-LG secondary structure was confirmed by the CD results. Molecular docking results agreed fully with the experimental results since the fluorescence studies also revealed the presence of two binding sites with a negative value for the Gibbs free energy of binding of oxali-palladium to β-LG. Furthermore, molecular docking and experimental results suggest that the hydrophobic effect plays a critical role in the formation of the oxali-palladium complex with β-LG. This agreement between molecular docking and experimental results implies that docking studies may be a suitable method for predicting and confirming experimental results, as shown in this study. Hence, the combination of molecular docking and spectroscopy methods is an effective innovative approach for binding studies, particularly for pharmacophores.

Synthesis, characterization, and cytotoxicity studies of a novel palladium(II) complex and evaluation of DNA-binding aspects

A new water-soluble palladium(II) complex, [Pd(bpy)(pyr-Ac]NO₃ in which bpy = 2,2'-bipyridine and pyr-Ac is 1-pyrrolacetato, has been synthesized and characterized by spectroscopic methods (¹H NMR, FT-IR, and UV-Vis), molar conductivity measurements, and elemental analysis. The results obtained from elemental analysis and conductivity measurements confirmed the stoichiometry of ligand and its complex while the characteristic peaks in UV-Vis and FT-IR and resonance peaks in (¹H NMR spectra confirmed the formation of ligand frameworks around the palladium ion. The 50% cytotoxic concentration (Ic₅₀) of new synthesized Pd(II) complex was determined by using MTT assay against human breast cancer cell line, T47D. The interaction between the Pd(II) complex with calf thymus DNA was studied at different temperatures by using absorption spectroscopy, fluorescence titration spectra, ethidium bromide displacement, and gel chromatography studies. The results obtained by absorption spectroscopy revealed that the Pd(II) complex can bind to DNA cooperatively at low concentrations. Several binding parameters in the above interaction were calculated by the fluorescence quenching method. The quenching mechanism was suggested to be the static quenching. The thermodynamic parameters: enthalpy change (ΔH °), entropy change (ΔS °), and Gibbs free energy (ΔG °), showed that van der Waals and hydrogen binding are predominant intermolecular forces between Pd(II) complex and DNA. These results were also consistent with the results obtained from Scatchard's plots.