Fluorescence Of BSA Research Articles

Silver(I) Complexes with Mefenamic Acid and Nitrogen Heterocyclic Ligands: Synthesis, Characterization, and Biological Evaluation.

Four Ag(I) complexes with mefenamato and nitrogen heterocyclic ligands, [Ag(2-apy)(mef)]2 (1), [Ag(3-apy)(mef)] (2), [Ag2(tmpyz)(mef)2] (3), and {[Ag(4,4'-bipy)(mef)]2(CH3CN)1.5(H2O)2}n (4), (mef = mefenamato, 2-apy = 2-aminopyridine, 3-apy = 3-aminopyridine, tmpyz = 2,3,5,6-tetramethylpyrazine, 4,4'-bipy = 4,4'-bipyridine), were synthesized and characterized. The interactions of these complexes with BSA were investigated by fluorescence spectroscopy, which indicated that these complexes quench the fluorescence of BSA by a static mechanism. The fluorescence data also indicated that the complexes showed good affinity for BSA, and one binding site on BSA was suitable for the complexes. The in vitro cytotoxicity of the four complexes against human cancer cell lines (MCF-7, HepG-2, A549, and MDA-MB-468) and one normal cell line (HTR-8) was evaluated by the MTT assay. Complex 1 displayed high cytotoxic activity against A549 cells. Further studies revealed that complex 1 could enhance the intracellular levels of ROS (reactive oxygen species) in A549 cells, cause cell cycle arrest in the G0/G1 phase, and induce apoptosis in A549 cells in a dose-dependent manner.

New palladium(II) metallates containing ON donor Schiff base ligand. synthesis, spectral characterization, x-ray crystallography, photo physical and in vitro cytotoxicity

Two new Palladium(II) complexes were synthesized by reacting (3‑hydroxy-naphthalene-2-carboxylic thiophen-2-ylmethylene-hydrazide) with [PdCl2(EPh3)2] (E = P, As). The complexes [Pd(L-N,O)Cl(PPh3)] (1) [Pd(L-N,O)Cl(AsPh3)] (2), HL = 3‑hydroxy-naphthalene-2-carboxylicthiophen-2-ylmethylenehydrazide formation was analysed through various spectroscopic investigations (IR, Uv-Visble, 1HNMR ) and structural confirmation was obtained from single crystal x-ray crystallography, which indicated that the complex 1 having distorted square planar geometry. DNA/protein binding ability of the ligand and complexes were commenced using absorption and emission titrations and found that the complex 2 have better binding ability with tyrosine and tryptophan residues and by quenching the fluorescence of BSA through static quenching mechanism. Their antioxidant and in vitro anticancer activities were assessed, where complex 2 displayed better radical scavenging properties and cancer cell death inducing ability. Further, DAPI staining assay was performed to detect the mode of cell death and found complex 2 having better towards to cell death.

Experimental and theoretical investigations of Erbium complex: DNA/BSA interaction, anticancer and antibacterial studies.

To assess the biological potential of an Er complex that contains a 2,2'-bipyridine ligand, various techniques such as multispectral and molecular modeling procedures were utilized to examine its DNA-binding ability, BSA binding affinity, antimicrobial effects, and anticancer properties. By analyzing fluorescent information and employing the vant' Hoff equation, important parameters such as the innate docking coefficient (Kb), Stern-Volmer coefficient (KSV), and thermodynamic properties including modifications in liberated energy (ΔG°), enthalpy (∆H°), and entropy (∆S°) were determined. The trial findings suggest that the compound can bind to DNA, primarily through groove binding. Additionally, the engagement between the Er compound and the protein BSA was examined using emission spectroscopy technique, revealing a powerful binding affinity between the compound and BSA. The Er complex binds to BSA primarily via hydrogen links and van der Waals forces, as indicated by the adverse values of ΔH° and ∆S°. Through a static quenching process, the complex significantly reduces the intrinsic fluorescence of BSA. Molecular binding calculations and rivalrous binding trials confirm that this compound dock to hydrophobic remains found in site III of BSA. Additionally, the Er complex demonstrates promising results in terms of its anticancer and antimicrobial activities based on screening tests.

Biomolecular interactions of 1,3-bis(2-arylimino)isoindolate-based palladium(II) complexes: Substitution kinetics, DNA/protein-binding, and molecular docking approaches

A series of 1,3-bis(2-arylimino)isoindoline Pd(II) complexes core viz.; Chlorido(1,3-bis(2-pyridylimino)isoindoline)palladium(II), Pd1, Chlorido(1,3-bis(4-methyl-2-pyridylimino)isoindoline)palladium(II), Pd2, Chlorido(1,3-bis(2-pyridylimino)benz(f)isoindoline)palladium(II), Pd3 and Chlorido(1,3-Bis(1-isoquinolylimino)isoindoline)palladium(II), Pd4 were synthesized, appropriately characterized and the crystal structure of Pd2 elucidated. The kinetics and mechanism of the substitution of the chloride ligand with thiourea ligands, Tu, Dmtu and Tmtu, from the complexes were investigated under pseudo-first-order conditions. The analyses were performed using stopped-flow analyzer or UV–visible spectrophotometer. The reactions proceeded through two consecutive steps for most complexes with exception of Pd4 showing only a single step. The substitution rates followed the order: Pd1>Pd2>Pd3>Pd4 due to varying degrees of steric influences and σ-/π-donations caused by the methylation and benzannulation on the cis-/trans-positions of the pyridyl rings of the BPI. The quenching of the fluorescence of CT-DNA/EB by the Pd(II) complexes suggests static quenching mechanism. The simulated docking of the complexes onto CT-DNA suggests they bind mainly in the minor grooves of DNA. The UV–Visible absorption titrations and quenching of tryptophan (Trp) fluorescence of BSA by the complexes depict reasonable interactions which occur mainly in the hydrophobic domains of the former. The order of strength of the interaction of the complexes with DNA or BSA is consistent with the rates of substitution kinetics.

DNA-binding affinity and molecular docking studies of the PEGylated binuclear palladacycle, BTC2, an efficient metallodrug against triple-negative breast cancer

Triple-negative breast cancer (TNBC) has a low five-year survival rate, especially if the cancer is diagnosed at a late stage and has already metastasized beyond the breast tissue. Current chemotherapeutic options for TNBC rely on traditional platinum-containing drugs like cisplatin, oxaliplatin and carboplatin. Unfortunately, these drugs are indiscriminately toxic, resulting in severe side effects and the development of drug resistance. Palladium compounds have shown to be viable alternatives to platinum complexes since they are less toxic and have displayed selectivity towards the TNBC cell lines. Here we report the design, synthesis, and characterization of a series of binuclear benzylidene palladacycles with varying phosphine bridging ligands. From this series we have identified BTC2 to be more soluble (28.38–56.77 μg/mL) and less toxic than its predecessor, AJ5, while maintaining its anticancer properties (IC50 (MDA-MB-231) = 0.58 ± 0.012 μM). To complement the previous cell death pathway study of BTC2, we investigated the DNA and BSA binding properties of BTC2 through various spectroscopic and electrophoretic techniques, as well as molecular docking studies. We demonstrate that BTC2 displays multimodal DNA binding properties as both a partial intercalator and groove binder, with the latter being the predominant mode of action. BTC2 was also able to quench the fluorescence of BSA, thereby suggesting that the compound could be transported by albumin in mammalian cells. Molecular docking studies revealed that BTC2 is a major groove binder and binds preferentially to subdomain IIB of BSA. This study provides insight into the influence of the ligands on the activity of the binuclear palladacycles and provides much needed information on the mechanisms through which these complexes elicit their potent anticancer activity.

Toxicity Study and Binding Analysis of Newly Synthesized Antifungal N-(4-aryl/cyclohexyl)-2-(pyridine-4-yl carbonyl) hydrazinecarbothioamide Derivative with Bovine Serum Albumin

The presence of the p-aryl/cyclohexyl ring in the N-(4-aryl/cyclohexyl)-2-(pyridine-4-yl carbonyl) hydrazine carbothioamide derivative (2C) is reported to enhance the antifungal properties when compared to those of itraconazole. Serum albumins present in plasma bind and transport ligands, including pharmaceuticals. This study explored 2C interactions with BSA using spectroscopic methods such as fluorescence and UV-visible spectroscopy. In order to acquire a deeper comprehension of how BSA interacts with binding pockets, a molecular docking study was carried out. The fluorescence of BSA was quenched by 2C via a static quenching mechanism since a decrease in quenching constants was observed from 1.27 × 105 to 1.14 × 105. Thermodynamic parameters indicated hydrogen and van der Waals forces responsible for the BSA-2C complex formation with binding constants ranging between 2.91 × 105 and 1.29 × 105, which suggest a strong binding interaction. Site marker studies displayed that 2C binds to BSA's subdomains IIA and IIIA. Molecular docking studies were conducted to further comprehend the molecular mechanism of the BSA-2C interaction. The toxicity of 2C was predicted by Derek Nexus software. Human and mammalian carcinogenicity and skin sensitivity predictions were associated with a reasoning level of equivocal, inferring 2C to be a potential drug candidate.

Evaluation the binding of chlorogenic acid with bovine serum albumin: Spectroscopic methods, electrochemical and molecular docking

Chlorogenic acid(CGA) is the common active phenolic acid in Chinese medicinal materials such as honeysuckle and eucommia. It is a class of small molecules with multiple activities such as antioxidant, inhibiting cancer cells, lowering blood sugar and lowering blood pressure. In this paper, UV–vis spectroscopy, fluorescence spectroscopy, circular dichroism, molecular dynamics simulation and cyclic voltammetry (CV) electrochemical analysis were used to investigate the mechanism about interaction between CGA and BSA. Based on fluorescence quenching analysis, CGA quenched the inherent fluorescence of BSA remarkably through a static mechanism. The obtained value of binding constant (Kb = 5.75 × 105 L·mol−1) revealed a high binding affinity between CGA and BSA. The simulated molecular docking showed that hydrophobic force were also involved in the interaction between BSA and CGA. This paper also investigate the effect of temperature and metal ions on the binding of CGA and BSA. When the temperature increased, the binding of BSA and CGA was destroyed. Metal ions affect both the structure of BSA and the combination of BSA and CGA. By studying the mechanism of CGA interaction with BSA, we elucidated the storage and transport mechanism of CGA in vivo under simulated human environment and temperature conditions.

Analysis of the level of oxidative stress by assessing the damage to the plasma protein serum albumin under the influence of an oxidizing agent

Oxidative stress, which leads to oxidative modification of various macromolecules, including proteins, is now considered an important pathogenetic link in many diseases. In this work, oxidative damage to a blood plasma protein, bovine serum albumin BSA, under the action of an oxidizing agent, hydrogen peroxide H2O2, was studied by spectrofluorometric method. The H2O2 concentration-dependent quenching of the intrinsic fluorescence of BSA is shown. BSA fluorescence quenching constants in hydrogen peroxide solutions are calculated by mathematical modeling methods. The dependences found in the fluorescence quenching constants are explained both by oxidative damage to the microenvironment of BSA tryptophan residues and by changes in the native conformation of protein globules upon oxidative damage. More significant peroxide damage to BSA occurs at lower pH values due to the fact that H2O2, as an oxidizing agent, acts more strongly in an acidic environment. The registered quenching of the protein's own fluorescence when damaged by an oxidizing agent can be used as a medical method for assessing the level of oxidative stress in the body in the diagnosis of a number of diseases.

Synthesis, structure, and biological properties of Cu(II) complexes based on diimine ligands

Three copper(II) complexes, [Cu(phen)2Cl](3,5-DNB) (3,5-HDNB) (1), [Cu(phen)(4-NB)2(H2O)] (2), and [Cu(2,2′-bipy)(4-NB)2(H2O)] (3), [phen = 1,10-phenanthroline, 2,2′-bipy = 2,2′-bipyridine, 3,5-DNB = 3,5-dinitrobenzoate anion, 3,5-HDNB = 3,5-dinitrobenzoic acid, 4-NB = 4-nitrobenzoate], have been synthesized and characterized. The interactions between three complexes and HS-DNA/BSA were determined by UV and fluorescence spectra. The results suggest that these copper(II) complexes interact with HS-DNA in an intercalative way and quench the intrinsic fluorescence of BSA via a static mechanism. The fluorescence data also indicated the complexes exhibited good binding propensity to BSA and the binding site available on BSA for the complexes was only one. The antiproliferative activity of the three complexes against several tumor cell lines (MCF-7, HepG-2, A549, and HeLa) was tested by MTT method. Three complexes displayed cytotoxicity against four tumor cells, but complex 3 is less cytotoxic than complexes 1-2. Moreover, the apoptosis was measured by the Annexin-V/PI double staining methods and the results demonstrated that complex 1 and 2 could induce apoptosis in MCF-7 and HeLa cells, respectively.

Synthesis, Characterization, Cytotoxicity and DNA/BSA Interaction of Pd(II) Complexes with Alkyl-Amine and 1,10-Phenanthroline

A novel series of Pd(II) complexes, [Pd(alkyl-amine)2(phen)](NO3)2, I-V, (where alkylamine is ethyl-, propyl-, butyl-, hexyl- and octyl-amine and phen is 1,10-phenanthroline) were synthesized and characterized based on FT-IR, 1H NMR, COSY-NMR, UV-Vis, molar conductivity, elemental analysis and density functional theory (DFT) approaches. The group, I-V, was screened for their primary in-vitro cytotoxic action against human cancer cell line MOLT-4, showing promising anti-tumor activities. Their interaction activity was tested using various spectroscopic techniques to explain the mode of binding between these compounds with CT-DNA and BSA. Results of UV-Vis studies showed that, at low concentrations, they all interacted effectively with CT-DNA and BSA. Studies of fluorescence emission spectra displayed that the complexes quenched CT-DNA pretreated with methylene blue (MB) and the intrinsic fluorescence of BSA via static quenching. Using thermodynamic parameters (ΔG°, ΔH°, and ΔS°) obtained from fluorescence studies, it was proposed that the hydrogen bonding and van der Waals forces play the main role between metal complexes with CT-DNA and BSA. The binding was spontaneous in all cases due to ΔG° <0. Also, Molecular docking simulation of all five Pd(II) complexes with DNA was performed to determine the compound with the highest binding affinity and investigate its binding mode. Next, molecular docking was utilized for this compound to study its BSA binding mode and affinity. The results obtained from this work may lay the foundation for structural changes exerted on DNA and BSA by Pd(II) antitumor compounds bearing various hydrocarbon chain length as well as structural relationship which are vital for pharmacokinetic and pharmacodynamics.

Luminescence studies of binding affinity of vildagliptin with bovine serum albumin

Vildagliptin (VDG)is a frontier drug for diabetes mellitus. It is prescribed both in the monotherapy as well as in an amalgamation with other antidiabetic drugs. Drug-serum protein binding is an essential parameter which influences ADME properties of the drug. In current study, binding of VDG with serum protein (bovine serum albumin: BSA) was investigated using multi-spectroscopic techniques. A computational approach was also employed to identify the binding affinity of VDG with BSA at both Sudlow I and II sites. An enzyme activity assay specific for esterase was also investigated to know the post-binding consequences of VDG with BSA. Fluorescence spectra of BSA samples treated with VDG shows static quenching with binding parameters for VDG-BSA complex show single class of equivalent binding stoichiometry(n = 1.331) and binding constant 1.1 x 104M−1 at 298.15 K. The binding constant indicates important role of non-polar interactions in the binding process. Fluorescence resonance energy transfer (FRET) analysis of VDG absorption spectra and emission spectrum of BSA confirmed no significant resonance in energy transfer. Synchronous fluorescence of BSA after binding with VDG show maximum changes in emission intensity at tryptophan (Trp) residues. Post binding with VDG, BSA conformation changes as suggested by circular dichorism (CD) spectra of BSA and this lead to enhanced protein stability as indicated by a thermal melting curve of BSA. Communicated by Ramaswamy H. Sarma

Crystal structures of three transition metal complexes with salicylaldehyde-4-hydroxy phenylacetyl acylhydrazone and their interactions with CT-DNA and BSA

A salicylaldehyde-4-hydroxy phenyl acetyl acyl hydrazone (C15H14N2O3, HL) and its three complexes ([CuLPy]NO3 (1), [CuLCl(EtOH)] (2) and [CoL2]NO3·EtOH, (3)) were synthesized. The single crystal X-ray diffraction results of 1, 2 and 3 showed that the coordination atoms (N and O atoms) in the complexes exhibited four-coordinated pyramidal, five-coordinated and six-coordinated octahedral geometries centered on the metal ions, respectively. TG-DTG techniques illustrated that the maximum thermal decomposition peak temperatures of these compounds were all higher than 200 ℃, exhibiting strong thermal stabilities. All four compounds, HL, 1, 2 and 3, quenched the intrinsic fluorescence of BSA by means of static processes, as investigated by fluorescence spectra, which suggested that these compounds could effectively combine with BSA to form non-fluorescent ground state complexes. The UV–vis spectra showed that HL, 1, 2 and 3 effectively combined with CT-DNA through intercalative modes. Microcalorimetry tests indicated that the interaction processes of HL, 1 and 2 with BSA and CT-DNA were all spontaneously exothermic and entropy reducing, and each of the interaction durations was within 50 min. The interactions of the four compounds with BSA and CTDNA were also simulated by the molecular docking method, showing that the four compounds had hydrogen bonds and hydrophobic interactions with BSA and CT-DNA. The antibacterial activities of HL, 1, 2 and 3 against S. aureus, P. aeruginosa, B. subtilis and E. coli were determined, revealing that 1 and 2 exhibit stronger inhibition activities against P. aeruginosa than gentamicin sulfate. Complexes 1 and 2 are potential alternative drugs to gentamicin sulfate in the future.

Five organotin complexes derived from hydroxycinnamic acid ligands: Synthesis, structure, in vitro cytostatic activity and binding interaction with BSA

Five new organotin(IV) hydroxycinnamates, [(Me3Sn)HL1]n (1), [(Ph3Sn)2L1]n (2), (n-Bu2Sn)(HL1)2 (3), [(Me3Sn)HL2]n (4), [(Ph3Sn)2L2]n (5), have been synthesized by the reactions of R3SnCl (R = Me, Ph) or n-Bu2SnO with the corresponding hydroxycinnamic acid proligands [H2L1 = 4-OH-3-CH3OC6H3CH=CHCOOH, ferulic acid; H2L2 = 4-OH-3,5-(CH3O)2C6H2CH=CHCOOH, sinapic acid]. All the complexes have been characterized by X-ray diffraction analysis, elemental analysis, NMR (1H, 13C and 119Sn), FT-IR, and PXRD (Powder X-ray diffraction). The structural analyses reveal that complexes 1, 2 and 5 display 1D infinite zig-zag chain structure, in which the 1D chains are further linked into a 3D supramolecular structure through intermolecular O-H···O interactions (for complex 1) or C-H···O interactions (for complex 5). Complex 3 presents mononuclear tin monomer and further constructs 2D planar supramolecular structure through intermolecular O-H···O interactions. Complex 4 displays 1D right-handed helical chain and further connects into a 3D supramolecular architecture through intermolecular O-H···O interactions. Furthermore, the in vitro cytostatic activity of complexes 1-5 was preliminarily evaluated by MTT method, and the results showed that complexes 2, 3 and 5 exhibited high cytostatic activity. The protein-binding properties of complexes 2, 3 and 5 were also investigated, which indicated these complexes could quench the intrinsic fluorescence of BSA in a static way.

Four triorganotin(IV) esters based on 3,5-bifluorobenzenetelluronic acid: Syntheses, structures, in vitro cytostatic activity and BSA-binding assessment

Four novel 3,5-bifluorobenzenetelluronic triorganotin(IV) esters, namely (3,5-F2C6H3TeOH)2(μ-O)2(OSnR3)4 (R = Me: 1, R = Ph: 2) and (3,5-F2C6H3TeOH)(OSnR3)4 (R = Me: 3, R = Ph: 4) have been synthesized and characterized by the reaction of deprotonated 3,5-bifluorobenzenetelluronic acid ligand and corresponding R3SnCl (R = Me, Ph). All the complexes have been characterized by means of elemental analysis, FT-IR, NMR (1H, 13C, 119Sn) spectroscopy, and X-ray crystallography. Structural analyses of these complexes reveal that complexes 1 and 2 exhibit centrosymmetric dimeric structure with an almost planar four-membered Te2(μ2-O)2 core in the center, while 3 and 4 form monomeric structure with a single Te center. The Te atoms adopt octahedral geometry in all the complexes. Complexes 1–4 could form 2D or 3D supramolecular structures through intermolecular C-H···F or C-H···O interactions. Preliminary in vitro cytostatic studies show that complexes 1–4 exhibit effective cytostatic activity against human cervix adenocarcinoma cell lines (HeLa) and human hepatocellular carcinoma cell lines (HepG-2). For further assessing apoptosis properties of complex 2, the levels of apoptosis were examined. The BSA-binding properties were investigated by means of fluorescence titration. The results indicate that complexes 1–4 could quench the intrinsic fluorescence of BSA.

Hydrophilic meso-substituted cyanine dyes in solution and in complexes with serum albumins: spectral properties and molecular docking study

The absorption and fluorescence spectral properties of three meso-substituted hydrophilic thiacarbocyanine dyes were studied in solutions and in noncovalent complexes with human and bovine serum albumins (HSA and BSA, respectively). The presence of alkyl substituents at the meso-position of the polymethine chain of the dyes determines the occurrence of a cis–trans equilibrium. Dyes form aggregates in aqueous media; the effect of electrolyte (NaCl) on aggregation has been studied. The interaction of the dyes with albumins leads to the decomposition of the aggregates and is accompanied by a shift in the isomeric equilibrium. Complexation with HSA leads to accumulation of dye monomers in the trans-form. However, in the case of BSA the cis-to-trans isomeric shift is incomplete. Using the fluorescence data, the effective binding constants of the trans-isomers with albumins (Ka) and the detection limits of albumin molecules (LD and LQ) were determined. The data obtained are indicative of high selectivity of some dyes to HSA compared to BSA. The results of molecular docking experiments correspond to the data obtained from the spectra. The influence of the dyes on intrinsic fluorescence of HSA and BSA was also studied, and fluorescence quenching, static in nature, was detected.

Synthesis, Cyclooxygenases Inhibition Activities and Interactions with BSA of N-substituted 1H-pyrrolo[3,4-c]pyridine-1,3(2H)-diones Derivatives.

Inhibition of cyclooxygenase is the way of therapeutic activities for anti-inflammatory pharmaceuticals. Serum albumins are the major soluble protein able to bind and transport a variety of exogenous and endogenous ligands, including hydrophobic pharmaceuticals. In this study, a novel N-substituted 1H-pyrrolo[3–c]pyridine-1,3(2H)-diones derivatives were synthesized and biologically evaluated for their inhibitory activity against cyclooxygenases and interactions with BSA. In vitro, COX-1 and COX-2 inhibition assays were performed. Interaction with BSA was studied by fluorescence spectroscopy and circular dichroism measurement. The molecular docking study was conducted to understand the binding interaction of compounds in the active site of cyclooxygenases and BSA. The result of the COX-1 and COX-2 inhibitory studies revealed that all the compounds potentially inhibited COX-1 and COX-2. The IC50 value was found similar to meloxicam. The intrinsic fluorescence of BSA was quenched by tested compounds due to the formation of A/E–BSA complex. The results of the experiment and molecular docking confirmed the main interaction forces between studied compounds and BSA were hydrogen bonding and van der Waals force.

Interaction of bis(alkylamine)dichloropalladium(II) complexes with CT-DNA and BSA; their synthesis, characterization, antitumor, and antibacterial evaluations

A series of five new and analogous palladium(II) alkylamine complexes of cisplatin derivatives such as cis-[Pd(alkyl-am)2Cl2], where alkyl-am is Ethyl-, Propyl-, Butyl-, Hexyl-, and Octyl-amine, have been prepared. They have been characterized by physicochemical methods such as FT-IR, 1H-NMR, UV-Vis, conductivity measurements and elemental analysis. These synthesized metal complexes were screened for their in-vitro antitumor activity against human MOLT-4 cells. Only [Pd(Octyl-am)2Cl2] showed moderate activity. They were also tested against some gram-negative (Escherichia coli) and gram-positive (Staphylococcus aureus) bacteria by measuring the values of IZ, MIC and MBC. All Pd(II) complexes displayed comparable activity with that of cefazoline as standard antibiotics. To clarify the mode of interaction between these compounds and CT-DNA and (BSA), their interaction behavior was checked using electronic absorption spectroscopy. Results indicated that all of the above mentioned Pd(II) complexes effectively interacted with CT-DNA and BSA at low concentration and the distance between the interacted Pd(II) complexes and BSA were in the range of 3.00–3.30 nm. Fluorescence emission studies revealed that the complexes quenched CT-DNA pretreated with methylene blue (MB) and the intrinsic fluorescence of BSA through static quenching procedure. Using the binding constant (K b) obtained from fluorescence studies, thermodynamic parameters (ΔG°, ΔH° and ΔS°) suggested that hydrogen bonding and van der Waals forces, as well as hydrophobic interaction, play the major role between metal complexes with CT-DNA and BSA. In all cases the binding forces were spontaneous owing to –ΔG°. Communicated by Ramaswamy H. Sarma

DNA and BSA Interaction, DNA Cleavage and &lt;i&gt;In Vitro&lt;/i&gt; Cytotoxicity of Copper(II) Complexes: [Cu(bba)(phen)](ClO&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt; is Promising Chemotherapeutic Scaffold

Three mononuclear copper(II) complexes of the type [Cu(bba)(bpy/phen/dpa)](ClO4)2 (1-3), where bba (N,N-bis(benzimidazol-2-ylmethyl)amine) and bpy (2,2’-bipyridine, 1) or phen (1,10-phenanthroline, 2) or dpa (2,2’-dipyridylamine, 3), have been isolated. The coordination geometry of 1 around copper(II) is square pyramidal. The electronic absorption (639-667 nm) and EPR spectral parameters (g||, ~2.25; A||, 181-186 × 10-4 cm-1; g||/A||, 122−134 cm) reveal that 1-3 possesses a square pyramidal geometry with CuN5 chromophore. Different spectral and electrochemical measurements clearly demonstrate partial intercalative interaction of 1-3 to CT DNA. Complexes strongly quench the intrinsic fluorescence of BSA through a static quenching procedure by forming BSA-(1/2/3) adducts, which are stabilized by hydrophobic interactions. The number of binding sites and binding constants were calculated. The energy transfer from BSA to Cu(II) complexes occurs with high probability. Notably, 1-3 exhibit more effective pUC 19 DNA cleavage in the presence of H2O2. Complexes 2 and 1 show remarkable cytotoxicity (IC50: 2, 2.17; 1, 8.33 mM) against human cervical carcinoma cells (HeLa) and more potent than cisplatin (IC50, 16.40 mM) while 3 exhibits less cytotoxicity (IC50, 20.82 mM). The DNA binding propensity, cleavage ability and cytotoxicity follow the order 2&gt;1&gt;3. Interestingly, they are non-toxic to healthy cells.

Refolding of protein unfolded by gemini surfactants using β-cyclodextrin and sodium dodecyl sulfate in aqueous medium: Study on role of spacer chain of surfactants

Interactions between protein, BSA and gemini surfactants, 12-n-12 (n = 3, 6, 8, 12) and step-by-step refolding of protein present as protein-gemini surfactant complex using β-cyclodextrin (β-CD)/sodium dodecyl sulfate (SDS) as stripping agents have been demonstrated by means of UV absorption, steady-state and time-resolved intrinsic fluorescence of BSA, circular dichroism spectroscopy, dynamic light scattering and field emitting scanning electron microscopy. This method is in contrast with the refolding of protein via artificial chaperone protocol. Mechanisms of interactions between protein-gemini complex and β-CD/SDS have been described. Role of spacer chain of gemini surfactants on the refolding of BSA unfolded by the surfactants has been explained. It has been observed that initially a gemini surfactant molecule with a long flexible spacer chain can more easily be stripped off by β-CD molecules forming simple inclusion complexes or nanotubes/rods depending on the concentration of β-CD. After the protein-micelles aggregates are dissociated, refolding of protein occurs more easily in case of gemini surfactant molecules with a short spacer chain. Method of β-CD induced refolding of a denatured protein has been validated by demonstrating refolding process in case of another protein, lysozyme. Unfolded proteins are also get refolded by SDS through the formation of catanions (mixed micelles, vesicles etc.).

Spectral and molecular modelling studies of sulfadoxine interaction with bovine serum albumin

The present study is focused on the binding interaction of sulfadoxine with bovine serum albumin under simulated physiological conditions using spectrofluorimetry. Various spectroscopic and other methods like UV–vis, Raman, FTIR, CD, lifetime measurement, cyclic voltammetry were also employed during the course of study. It was noticeable that sulfadoxine did quench the intrinsic fluorescence of BSA via static quenching process. UV–vis study enabled the calculation of association constant, Kass for the interaction of BSA and sulfadoxine. The change in the secondary structure of BSA and binding mechanism was investigated with the spectral and docking studies. The meticulous investigation of competitive binding sites using various probes was studied and it was clear that drug binding was non-specific. Effect of some co-existent drugs and metal ions were examined which may help in the controlled release of drugs.