Fluorescence Of BSA Research Articles

Cytotoxicity of Ru(II) piano–stool complexes with chloroquine and chelating ligands against breast and lung tumor cells: Interactions with DNA and BSA

The synthesis and spectroscopic characterization of nine π-arene piano–stool ruthenium (II) complexes with aromatic dinitrogen chelating ligands or containing chloroquine (CQ), are described in this study: [Ru(η6-C10H14)(phen)Cl]PF6 (1), [Ru(η6-C10H14)(dphphen)Cl]PF6 (2), [Ru(η6-C10H14)(bipy)Cl]PF6 (3), [Ru(η6-C10H14)(dmebipy)Cl]PF6 (4) and [Ru(η6-C10H14)(bdutbipy)Cl]PF6 (5), [Ru(η6-C10H14)(phen)CQ](PF6)2 (6), [Ru(η6-C10H14)(dphphen)CQ](PF6)2 (7), [Ru(η6-C10H14)(bipy)CQ](PF6)2 (8), [Ru(η6-C10H14)(dmebipy)CQ](PF6)2 (9): [1,10-phenanthroline (phen), 4,7-diphenyl-1,10-phenanthroline (dphphen), 2,2′-bipyridine (bipy), 5,5′-dimethyl-2,2′-bipyridine (dmebipy), and 4,4′-di-t-butyl-2,2′-bipyridine (dbutbipy)]. The solid state structures of five ruthenium complexes (1–5) were determined by X-ray crystallography. Electrochemical experiments were performed by cyclic voltammetry to estimate the redox potential of the RuII/RuIII couple in each case. Their interactions with DNA and BSA, and activity against four cell lines (L929, A549, MDA-MB-231 and MCF-7) were evaluated. Compounds 2, 6 through 9, interact with DNA which was comparable to the one observed for free chloroquine. The results of fluorescence titration revealed that these complexes strongly quenched the intrinsic fluorescence of BSA following a static quenching procedure. Binding constants (Kb) and the number of binding sites (n~1) were calculated using modified Stern–Volmer equations. The thermodynamic parameters ΔG at different temperatures were calculated and subsequently the values of ΔH and ΔS were also calculated, which revealed that hydrophobic and electrostatic interactions play a major role in the BSA–complex association. The MTT assay results indicated that complexes 2, 5 and 7 showed cytostatic effects at appreciably lower concentrations than those needed for cisplatin, chloroquine and doxorubicin.

Spectroscopic study on binding of gentisic acid to bovine serum albumin

The interaction of (gentisic acid) GA with (bovine serum albumin) BSA has been studied by different spectroscopic techniques. GA is a monoanionic specie at the working pH of 7.4, it was determined by combining UV–Vis absorption spectroscopy and theoretical calculations. A set of fluorescence quenching experiments at different temperatures was carried out employing the native fluorescence of BSA. A Stern–Volmer constant (KSV) of (2.07±0.12)×104mol−1L and a binding constant (Ka) of (8.47±4.39)×103 were determined at 310K. The static quenching caused by the BSA–GA complex formation seems to play a significant role in the overall quenching process. A single binding site on BSA for GA was observed. ΔH=−55.6±0.2kJmol−1 and ΔS=−104.3±0.6Jmol−1K−1 were determined in a set of experiments on the dependence of Ka with the temperature. The binding process is, therefore, spontaneous and enthalpy-driven. Van der Waals forces and hydrogen bonds could also play the major role in the binding mode. The secondary structure changes of BSA in the absence and presence of GA were studied by FTIR and UV–Vis absorption spectroscopy.

A comparative study of cytotoxicity and interaction with DNA/protein of five transition metal complexes with Schiff base ligands

Five transition metal complexes NiL12 (1), CuL12 (2), ZnL12 (3), [MnL12(N3)]n·nCH2Cl2 (4), CuL22 (5) {HL1=3-{[2-(2-hydroxy-ethoxy)-ethylimino]-methyl}-naphthalen-2-ol, HL2=2-{[2-(2-hydroxy-ethoxy)-ethylimino]-methyl}-phenol} have been synthesized and fully characterized. In all of the complexes, the ligands coordinated to the metal ion in a negative fashion via O and N donor atoms. The X-ray structures of nickel complex 1 and copper complexes 2 and 5 are four-coordinated monomers and show slightly distorted square-planar geometry in the vicinity of the central metal atom. Zinc complex 3 exhibits a four-coordinated tetrahedral structure. Differently, manganese complex 4 reveals a six-coordinated octahedral structure, one-dimensional chain is linked by azide in the end-to-end mode. In vitro cytotoxicity of these complexes to various tumor cell lines was assayed by the MTT method. The results showed that most of these metal-Schiff base complexes exhibited enhanced cytotoxicity than Schiff base ligands, which clearly implied a positive synergistic effect. Moreover, these complexes appeared to be selectively active against certain cell lines. The interactions of these metal complexes with CT-DNA were investigated by UV–vis, fluorescence and CD spectroscopy, the results indicated that these complexes are metallointercalators and can interact with CT-DNA. The study of interaction between complexes and BSA indicated that all of the complexes could quench the intrinsic fluorescence of BSA in a static quenching process.

A label-free fluorescent assay for free chlorine in drinking water based on protein-stabilized gold nanoclusters

Bovine serum albumin stabilized Au nanoclusters (BSA–AuNCs) were demonstrated as a novel fluorescence probe for sensitive and selective detection of free chlorine in drinking water. The fluorescence of BSA–AuNCs was found to be quenched effectively by the free chlorine, and the decrease in fluorescence intensity of BSA–AuNCs allowed the sensitive detection of free chlorine in the range of 0.8–800μM. The detection limit is 0.50μM at a signal-to-noise ratio of 3. The present fluorescent assay for free chlorine possesses low detection limit, wide linear range and good selectivity. Real tap water samples were analyzed with satisfactory results, which suggested its potential for water quality analysis.

Interaction of erucic acid with bovine serum albumin using a multi-spectroscopic method and molecular docking technique

Overconsumption of erucic acid has been shown to cause heart damage in animals. The aim of this study is to evaluate the binding behaviour between erucic acid and bovine serum albumin using multi-spectroscopic methods and a molecular docking technique under physiological conditions. We find that erucic acid can quench the intrinsic fluorescence of BSA by dynamic quenching and there is a single class of binding site on BSA. In addition, the thermodynamic functions ΔH and ΔS are 119.14kJmol−1 and 488.89Jmol−1K−1, indicating that the hydrophobic force is a main acting force. Furthermore, the protein secondary structure changes with an increase in the content of α-helix, measured using synchronous fluorescence, circular dichroism and Fourier transform infrared spectroscopies. The molecular docking results illustrate that erucic acid can bind with the subdomain IIA of the BSA, and hydrogen bonding is also an acting force.

Binding of (−)-epigallocatechin-3-gallate with thermally-induced bovine serum albumin/ι-carrageenan particles

Novel thermally-induced BSA/ι-carrageenan particles are used as a protective carrier for (−)-epigallocatechin-3-gallate (EGCG). The addition of EGCG to BSA/ι-carrageenan particles can highly quench the intrinsic fluorescence of BSA, which is explained in terms of the binding of EGCG to the hydrophobic pockets of BSA mainly through the hydrophobic force. According to the double logarithm equation, the binding constant is determined as 1.1×108M−1 for the binding of EGCG with BSA/ι-carrageenan particles. The high binding affinity is ascribed to both the molecular structure of EGCG and the partial unfolding state of BSA in BSA/ι-carrageenan particles. The circular dichroism spectra and calculated α-helix of BSA suggest that the bound EGCG leads to a more random secondary structure of BSA. Furthermore, BSA/ι-carrageenan particles are found to be superior to native BSA and pure BSA particles for improving the stability and radical scavenging activity of EGCG.

Synthesis, crystal structure, magnetism, and biological activities of an oxo-bridged diiron(III) complex

An unsymmetrical oxo-bridged diiron(III) complex [Fe2L2(μ-O)], {H2L = trans-N,N′-bis-(2hydroxy-1-naphthalidehydene)-cyclohexanediamine} has been synthesized and characterized by various physico-chemical techniques. In the complex, each deprotonated bi-anionic L2− serves as a terminal tetradentate ligand (N2O2) and coordinates to one Fe to form a [FeL]+ unit. Two [FeL]+ units are further linked by an oxo-bridge to construct the binuclear oxo-Fe species with intramolecular Fe–Fe separation of 3.38 Å. Variable-temperature magnetic susceptibility studies revealed a strong antiferromagnetic interaction between two iron centers with J of −112 cm−1. The interaction of the complex with CT-DNA was studied by various spectroscopic and viscosity measurements, which indicated that the complex could interact with CT-DNA through intercalation. In addition, the complex is able to cleave pBR322 DNA in the presence of H2O2. Furthermore, the interaction of the compound with BSA was also investigated, which indicated that the complex could quench the intrinsic fluorescence of BSA by a static quenching mechanism.

Cu2 + modulated BSA–Au nanoclusters: A versatile fluorescence turn-on sensor for dopamine

In this work, Cu2+ modified BSA stabilized gold nanoclusters (BSA–Au NCs) were fabricated for the fluorescence turn-on detection of dopamine, an important catecholamine neurotransmitter. The fluorescence of BSA–Au NCs was initially quenched by the Cu2+ ion, and then the addition of dopamine molecule causes the retrieval fluorescence by binding with the metal ion and removing it from the surface of BSA–Au NCs. The mode of interaction between metal ion with BSA–Au nanoclusters and dopamine was studied using fluorescence lifetime measurements, circular dichroism and infrared spectroscopy. The developed Cu2+ quenched BSA-Au nanocluster demonstrated high selectivity and sensitivity towards dopamine over other catecholamines and coexisting substances with a limit of detection 0.01μM. The feasibility of the new turn on sensor in different real samples was demonstrated. The recovery of fluorescence by spiked analyte in human serum and urine samples ranged from 92 to 98% attesting the validity of the developed method.

Synthesis, characterization, and biological activities of two Cu(II) and Zn(II) complexes with one polyquinoline ligand

Two new complexes, [CuLCl]ClO4 (1) and [Zn2L2SO4(H2O)2](ClO4)2 (2) [L=N,N-bis(quinolin-2-ylmethyl)quinolin-8-amine], have been synthesized and structurally characterized. The interactions of two complexes with CT-DNA have been investigated by UV absorption, fluorescence spectroscopy, viscosity measurements and gel electrophoresis under physiological conditions. Results show that the complexes bind to CT-DNA with a moderate intercalative mode and exhibit efficient DNA cleavage activity on UV-A light of 365nm. Furthermore, two complexes could quench the intrinsic fluorescence of BSA in a static quenching process based on BSA binding experiments. Notably, in vitro cytotoxicity study of two complexes on four human tumor cells lines (7404, HeLa, MCF-7, and HepG-2) indicate that both of them have the potential to act as effective anticancer drugs with low IC50 values.

Probing the interaction of ferrocene containing hyperbranched poly-ester with model plasma protein: Effect on the interaction mechanism and conformational change

Interaction mechanism and conformational change of model plasma protein-bovine serum albumin (BSA) induced by ferrocenyl-functionalized hyperbranched polyester (HBPE-Fc) were investigated using cyclicvoltammetry (CV), differential pulsed voltammetry (DPV), fluorescence, UV–vis absorption spectrometry and circular dichroism (CD). Some complicated interactions occurred between BSA and HBPE-Fc and the new redox centers appeared in the BSA/HBPE-Fc complex that changed and hindered the electron transfer of Fe/Fe2+. Fluorescence quenching data showed that the fluorescence of BSA was statically quenched by HBPE-Fc, which implied that ground state complex formed between BSA and HBPE-Fc. van der Waals force and hydrogen bond played major roles in the interaction of HBPE-Fc with BSA. The binding constant Ka for HBPE-Fc–protein interaction is in the order of 106 at room temperature indicates that there is a strong interaction between HBPE-Fc and BSA. Synchronous, three-dimensional fluorescence and CD studies indicated that the interaction of BSA with HBPE-Fc induced conformational changes in BSA with overall decrease in the α-helical structure and increase in β-pleated sheet structure. The molecular model of the interaction between HBPE-Fc and BSA was also presented according to the results in this study.

INVESTIGATION OF THE FLUORESCENCE QUENCHING OF BOVINE AND HUMAN SERUM ALBUMIN BY RUTHENIUM COMPLEX

The binding of [RuCl2(L)] (L = N,N-bis(7-methyl-2-pyridylmethylene)-1,3-diiminopropane) to bovine and human serum albumin was investigated by the fluorescence quenching technique. The comparison of the quenching effect of serum albumin fluorescence by ruthenium complex allowed the estimation of subdomain IB in BSA and subdomain IIA in HSA as the binding sites for this complex. The results of fluorescence titration revealed that ruthenium complex quenches the intrinsic fluorescence of BSA through a dynamic quenching mechanism, while HSA has a static quenching mechanism. The thermodynamic parameters indicated that hydrophobic forces played a major role in the binding of ruthenium complex to proteins. The process of binding was a spontaneous process in which Gibbs free energy change was negative.

A fluorescent spectroscopy and modelling analysis of anti-heparanase aptamers–serum protein interactions

Aptamers are short, single stranded oligonucleotide or peptide molecules that bind a specific target molecule and can be used for the delivery of therapeutic agents and/or for imaging and clinical diagnosis. Several works have been developed aiming at the production of aptamers and the study of their applications, but few results have been reported on plasmatic dynamics of such products. Aptamers against the heparanase enzyme have been previously described. In this work, the interactions of two constructs of the most promising anti-heparanase aptamer (molecular weights about 9200Da and 22000Da) to human and bovine serum albumins were studied by fluorescence quenching technique. Stern–Volmer graphs were plotted and quenching constants were estimated. Stern–Volmer plots obtained from experiments carried out at 25°C and 37°C showed that the quenching of fluorescence of HSA and BSA by the low molecular weight aptamer was a collisional phenomenon (estimated Stern–Volmer constant: 3.22 (±0.01)×105M−1 for HSA at 37°C and 2.47 (±0.01)×105M−1 for HSA at 25°C), while the high molecular weight aptamer quenched albumins by static process (estimated Stern–Volmer constant: 4.05 (±0.01)×105M−1 for HSA at 37°C and 6.20 (±0.01)×105M−1 for HSA at 25°C), interacting with those proteins constituting complexes. Linear Stern–Volmer plot from HSA titrated with the low MW aptamer suggested the existence of a single binding site for the quencher in this albumin. Differently, for aptamer 2, the slightly downward curvature of the Stern–Volmer plot of the titration for that albumin suggested a possible conformational change that led to the exposition of lower affinity binding sites in HSA at 25°C. Similarly, although short aptamerdoes not appear to form a stable complex (collisional interaction), the longer aptamer is found to form a stable complex with HSA. In addition, the behaviour of quenching curves for HSA and BSA and values estimated for ratio R1/R2 from model developed by Silva et al. suggest that the primary binding site in both aptamers is located closer to the tryptophan residue in sub domain IIA. It is likely that both aptamers are competing for the same primary site in albumin.

Binding of Curcumin with Bovine Serum Albumin in the Presence of ι-Carrageenan and Implications on the Stability and Antioxidant Activity of Curcumin

This work studied the influences of formation of BSA/ι-carrageenan complexes on the binding, stability, and antioxidant activity of curcumin. In the presence of BSA and ι-carrageenan, curcumin gives higher intensities of absorption and fluorescence than free curcumin and curcumin only combined with BSA. The added ι-carrageenan is observed to promote curcumin for quenching the instrinsic fluorescence of BSA. These results are explained in terms of the formation of BSA/ι-carrageenan complexes, which help to stabilize the folded structure of BSA for providing curcumin with a more hydrophobic microenvironment. The small difference in anisotropy values of curcumin with BSA alone and of BSA/ι-carrageenan complexes suggests that ι-carrageenan acts as outer stretch conformation in BSA/ι-carrageenan complexes but does not directly disturb the hydrophobic pockets inside BSA, where curcumin is hydrophobically located. The determined values of the binding constant are higher for curcumin with BSA/ι-carrageenan complexes than with BSA alone. Moreover, BSA/ι-carrageenan complexes are found to be superior to single BSA for enhancing the stability and DPPH radical-scavenging ability of curcumin.

Spectroscopic investigations on the binding of leucomalachite green to bovine serum album

The interaction of bovine serum with leucomalachite green (LMG) was investigated by spectroscopic methods. LMG was found to quench the intrinsic fluorescence of BSA by dynamic quenching. High quenching constant suggested that LMG can form a complex with BSA. Binding constant and number of binding site were determined. The thermodynamic parameters suggested the main interacting force is hydrophobic forces. The effect of LMG on the conformation of BSA was analyzed by synchronous fluorescence spectroscopy. RLS spectra were also used to reconfirm the formation of complex between BSA and LMG.

Oxidation of Bovine Albumin by Hypochlorous and Hypobromous Acids: Structural and Functional Alterations

Aims: Hypochlorous (HOCl) and hypobromous (HOBr) acids are among the most powerful oxidants produced by the innate immune cells. Albumin is the predominant protein in most body fluids and is considered the most important antioxidant of blood plasma. Study Design: Oxidation of bovine albumin (BSA) and study of its structural and functional alterations. Place and Duration of Study: Faculty of Science and Faculty of Pharmaceutical Science, University of the State of Sao Paulo UNESP, between June and December 2012. Methodology: BSA was oxidized with excess of HOCl or HOBr and its structural and functional alterations were analyzed by spectroscopic techniques as UV-Vis absorption, intrinsic and synchronous fluorescence, fluorescence quenching, Rayleigh scattering and circular dichroism. Results: Both oxidants were able to deplete the intrinsic fluorescence of BSA, but HOBr was more effective than HOCl. The alterations in the synchronous fluorescence, UV-Vis absorption, and the appearance of a fluorescence band centered at 450 nm confirmed the difference between the oxidants. The oxidation did not induce aggregation of BSA as measured by Rayleigh scattering. The far-UV circular dichroism spectra showed a loss in the helical content and the near-UV-circular dichroism showed an alteration in the tertiary structure; HOBr was the more effective of the oxidants in this case. However, the oxidations did not induce significant alterations in the binding capacity of BSA, which was evaluated using hydrophobic (norfloxacin) and hydrophilic (ascorbic acid) drugs. Conclusion: These results suggest that, although highly susceptible to oxidation, the alterations did not inhibit BSA’s physiological function as a transport protein.

Study of the Interaction between Three New Amantadine Schiff Bases and BSA by the Multi-Spectroscopic Method

The binding of three amantadine schiff bases (ASBs) to BSA was investigated by fluorescence spectroscopy, UV-Vis spectroscopy and circular dichroism (CD). The results showed that the fluorescence of BSA was quenched remarkably by these compounds via a combination of static and dynamic quenching. Binding constant (Ka), number of binding sites (n), and the binding distance (r) between three ASBs and BSA were calculated in this study. Displacement experiments were performed to identify these compounds binding sites on BSA, and the results showed that site I was the main location for ASBs binding to BSA. Moreover, synchronous fluorescence spectra and CD data revealed that ASBs induced the conformational change of BSA.

Molecular spectroscopic on interaction between Methyl hesperidin and Buman serum albumin

The interaction of Methyl hesperidin (MH) with Buman serum albumin was studied by spectroscopic methods including Fluorescence quenching technology, UV absorbance spectra and Fourier transform infrared (FT-IR) spectroscopy under simulative physiological conditions. The result of fluorescence titration revealed that Methyl hesperidin could quench the intrinsic fluorescence of BSA and the quenching mechanism should be a combined quenching process. The binding constants at three temperatures (296, 303, and 310K) were 1.82, 2.69, and 3.4×104Lmol−1, respectively. The distance between donor (BSA) and acceptor (MH) was 5.54nm according to the Förster theory of non-radiation energy transfer. In addition, FT-IR spectroscopy showed that the binding of MH to BSA changed the secondary structure of protein.

Partial characterization of indigo (Polygonum tinctorium Ait.) plant seeds and leaves

The aim of this study was to assess the contents of indigo's bioactive compounds, its antioxidant and anticancer activities in acetone, hexane and DMSO extracts and to compare the overall bioactivity with another more used medicinal plant named prolipid. It was found that the contents of the bioactive compounds in the studied extracts from different parts of indigo plant varied (P<0.05): the significantly highest content of polyphenols and flavonoids was in DMSO extract of prolipid, flavanols – in acetone extract of brown seeds (P<0.05 in both cases) and tannins – in DMSO extract of green leaves, but not significantly (P>0.05). Also the level of antioxidant activity was different: the highest antioxidant activity of all studied samples was in prolipid: according to ABTS, FRAP and CUPRAC tests in DMSO extract (P<0.05 in all 3 cases), and only in acetone extract according to DPPH was not significant (P>0.05). The correlations between polyphenol compounds and the antioxidant activities were relatively high. DPPH kinetic measurements were used to compare and distinguish the antiradical activity among indigo extracts by multivariate analysis. The FT-IR spectroscopy evaluated the presence of polyphenols. The interaction between DMSO polyphenol extracts of indigo plant and BSA showed that indigo has a strong ability as other medicinal plants such as prolipid to quench the intrinsic fluorescence of BSA by forming complexes and was measured by 3-dimensional fluorescence (3D-FL). The highest anticancer activity was in prolipid in concentrations of 800μg/mL against Calu-6, following by indigo brown leaves. In conclusion, organic extracts of indigo brown leaves were analyzed for their antioxidant and anticancer activities and compared with prolipid, using polyphenols composition, antioxidant activities and fluorescence properties. The indigo ability to quench the intrinsic fluorescence of BSA, relatively high content of phenolic compounds and anticancer properties can be used as medicinal plant.

Crystal Structures, Interactions with Biomacromolecules and Anticancer Activities of Mn(II), Ni(II), Cu(II) Complexes of Demethylcantharate and 2-Aminopyridine

Three novel transition metal complexes (Hapy)(2)[M(DCA)(2)]·6H(2)O (M = Mn(II) (1), Ni(II) (2), Cu(II) (3); DCA = demethylcantharate, 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylate, C(8)H(8)O(5); Hapy = 2-aminopyridine acid, C(5)H(7)N(2)) were synthesized and characterized by elemental analysis, infrared spectra, thermogravimetric analysis and X-ray diffraction. DNA binding properties of the complexes were investigated by electronic absorption spectra, fluorescence spectra and viscosity measurements. Results indicated the complexes could bind to DNA through partial intercalation mode with binding constants K ( b )/(L·mol(-1)) of 1.91 × 10(4) (1), 5.13 × 10(4) (2) and 1.12 × 10(5) (3) at 298 K. Meanwhile, the interactions of the complexes with BSA were also studied by fluorescence spectra. The results suggested that the complexes could quench the fluorescence of BSA through static quenching with the binding constants K ( A )/(L·mol(-1)) of 1.44 × 10(6) (1), 1.14 × 10(7) (2) and 2.98 × 10(4) (3). And the main contribution was tryptophan residues of BSA. The antiproliferative activity test revealed that complexes showed more intense inhibition ratios against human hepatoma cells lines and human gastric cancer cells lines in vitro. Copper(II) complex (3) possesses the strongest inhibition ratio against human hepatoma cells.

Chemical Composition, Antioxidant and Anticancer Effects of the Seeds and Leaves of Indigo (Polygonum tinctorium Ait.) Plant

Seeds and leaves of indigo (Polygonum tinctorium Ait.) plant were investigated and compared with another medicinal plant named prolipid for their properties such as chemical composition, antioxidant, and anticancer effects by Fourier transform infrared, three-dimensional fluorescence spectroscopy, and electrospray ionization-MS in negative mode. It was found that polyphenols, flavonoids, and flavanols were significantly higher in prolipid (P<0.05), following by indigo mature leaves, immature leaves, and seeds. Methanol extract of mature indigo leaves in comparison with the ethyl acetate extract showed higher inhibition of proliferation. The interaction between polyphenol extracts of indigo mature leaves and BSA showed that indigo has a strong ability, as other widely used medicinal plants, to quench the intrinsic fluorescence of BSA by forming complexes. In conclusion, indigo mature leaves were compared with prolipid. High content of bioactive compounds, antioxidant, fluorescence, and antiproliferative properties of indigo justifies the use of this plant as a medicinal plant and a new source of antioxidants.