Synthesis,CMC Determination,Antimicrobial Activity and Nucleic Acid Binding of A Surfactant Copper(II) Complex Containing Phenanthroline and Alanine Schiff-Base

A new water-soluble surfactant copper(II) complex [Cu(sal-ala)(phen)(DA)] (sal-ala = salicylalanine, phen = 1,10-phenanthroline, DA = dodecylamine), has been synthesized and characterized by physico-chemical and spectroscopic methods. The critical micelle concentration (CMC) values of this surfactant–copper(II) complex in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 303, 308, 313. 318 and 323 K) served for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (ΔG⁰m, ΔH⁰m and ΔS⁰m). The interaction of this complex with nucleic acids (DNA and RNA) has been explored by using electronic absorption spectral titration, competitive binding experiment, cyclic voltammetry, circular dichroism (CD) spectra, and viscosity measurements. Electronic absorption studies have revealed that the complex can bind to nucleic acids by the intercalative binding mode which has been verified by viscosity measurements. The DNA binding constants have also been calculated (K_b?=?1.2?×?10⁵ M^?1 for DNA and K_b?=?1.6?×?10⁵ M^?1 for RNA). Competitive binding study with ethidium bromide (EB) showed that the complex exhibits the ability to displace the DNA-bound-EB indicating that the complex binds to DNA in strong competition with EB for the intercalative binding site. The presence of hydrophobic ligands, alanine Schiff-base, phenanthroline and long aliphatic chain amine in the complex were responsible for this strong intercalative binding. The surfactant–copper (II) complex was screened for its antibacterial and antifungal activities against various microorganisms. The results were compared with the standard drugs, amikacin(antibacterial) and ketokonazole(antifungal).     

Multi-spectroscopic and molecular docking studies on the interaction of new phthalimides with calf-thymus DNA: In vitro free radical scavenging activities

ABSTRACT

In this study, we report the synthesis and biological evaluation of novel phthalimide based Schiff base derivatives as promising antioxidant and DNA-binding agents. The structural investigation of the synthesized compounds was determined by spectral and elemental analysis. In vitro DNA-binding studies of title compounds were carried out by UV–Vis, fluorescence, circular dichroism spectroscopic techniques, cyclic voltammetry, thermal denaturation studies, and hydrodynamic measurements to investigate their potential as DNA-binding agents. The DNA binding constant (K_b) of target compounds was obtained from absorption studies between 1.2 × 10⁵ M^?1 and 1.27 × 10⁵ M^?1, respectively, suggesting that the test compounds have shown good affinity toward calf-thymus DNA. The experimental results of DNA-binding studies reveal a non-intercalative mode of binding between DNA and the synthesized compounds, most probably groove binding. In addition, molecular docking techniques were performed to rationalize the observed binding affinities with the target DNA. Furthermore, antioxidant and free radical scavenging activities of the synthesized compounds were carried out to find out their pharmacological potential. The results indicate that the title compounds displayed good antioxidant activity against DPPH (IC₅₀: 0.727 and 0.656 mg/mL) and H₂O₂ radicals (IC₅₀: 1.072 and 0.911 mg/mL) comparable to standard ascorbic acid.     

Investigation of the Interaction Between Rutin and Trypsin in Solution by Multi-Spectroscopic Method

ABSTRACT

The interactions between rutin and trypsin were investigated by UV-Vis absorption, CD, fluorescence, resonance light-scattering spectra, synchronous fluorescence, and three-dimensional fluorescence spectra techniques under physiological pH 7.40. Rutin effectively quenched the intrinsic fluorescence of trypsin via static quenching. The enthalpy change and entropy change were estimated to be ?8.23 kJ·mol^?1 and 53.66 J·mol^?1·K^?1 according to the van't Hoff equation. The process of binding rutin to trypsin was a spontaneous molecular interaction procedure. This result indicates that hydrophobic and electrostatic interactions played a major role in stabilizing the complex. The conformation of trypsin was discussed by CD, synchronous, and three-dimensional fluorescence techniques.     

Synthesis, Characterization, Antioxidant Activity and DNA-Binding Studies of Three Rare Earth (III) Complexes with 1-(4-Aminoantipyrine)-3-tosylurea Ligand

1-(4-Aminoantipyrine)-3-tosylurea (H₂L) and its three lanthanide (III) complexes, M(H₂L)₃ 3NO₃ [where M = Nd(III), Sm(III) and Eu(III)], have been synthesized and characterized. In addition, the DNA-binding properties of the three complexes have been investigated by UV–vis (ultraviolet and visible) absorption spectroscopy, fluorescence spectroscopy, circular dichroism (CD) spectroscopy, cyclic voltammetry, and viscosity measurements. Results suggest that the three complexes bind to DNA via a groove binding mode. Furthermore, the antioxidant activity (superoxide and hydroxyl radical) of the metal complexes was determined by using spectrophotometer methods in vitro. These complexes were found to possess potent antioxidant activity and be better than standard antioxidants like vitamin C and mannitol. Absorption spectra of the complex 3 inTris-HCl buffer upon addition of calf-thymus DNA. [complex]=1×10^-5 M, [DNA]=(0-1) ×10^-5 M. Arrow shows the absorbance changing upon increasing DNA concentrations. Inset: plots of [DNA]/(ε_a – ε_f) versus [DNA] for the titration of DNA with the complex.     

Synthesis,DNA/HSA Interaction Spectroscopic Studies and In Vitro Cytotoxicity of a New Mixed Ligand Cu(II) Complex

A new mixed ligand copper(II)-dipeptide complex with 2-(2′-pyridyl)benzothiazole (pbt), [Cu(Gly-L-leu)(pbt)(H₂O)]·ClO₄ (Gly-L-leu = Glycyl-L-leucine anion) was synthesized and characterized by various physico-chemical means. The DNA binding and cleavage properties of the complex investigated by viscosity, agarose gel electrophoresis and multi-spectroscopic techniques (UV, circular dichroism (CD) and fluorescence) showed that the complex was bound to CT-DNA through intercalation mode with moderate binding constant (K _b = 3.132 × 10⁴ M^?1), and cleaved pBR322 DNA efficiently (~ 5 μM) in the presence of Vc, probably via an oxidative mechanism induced by ?OH. Additionally, the interaction of the complex with human serum albumin (HSA) was explored by UV-visible, CD, fluorescence, synchronous fluorescence and 3D fluorescence spectroscopy. The complex exhibits desired affinity to HSA through hydrophobic interaction. Moreover, the cytotoxicity of the complex against three human carcinoma cell lines (HeLa, HepG2 and A549) was evaluated by MTT assay, which showed that the complex had effective cytotoxicity and higher inhibition toward A549 cell lines with IC₅₀ of 38.0 ± 3.2 μM.     

SPECTRAL STUDIES ON THE BINDING OF A BISACRIDINIUM DERIVATIVE LUCIGENIN WITH DOUBLE HELIX DNA

ABSTRACT

In this paper, the noncovalent binding of the cationic reagent lucigenin (LC) to DNA was investigated using spectroscopic methods. The results from absorption, circular dichroism and fluorescence studies demonstrated that LC could intercalate into the helix of DNA. Polarization and melting studies further supported the intercalation binding of LC with DNA. The binding constant was obtained by varying the DNA concentration, while keeping the concentration of LC constant. It was of the order of 10⁴ mol^?1 L in DNA base pairs. The experiment also showed that electrostatic interaction played a significant role in the intercalation of LC with DNA. It is supposed to be because of being attracted first by anionic DNA that LC can be intercalated into the interior of the DNA double helix. This research offers a new intercalation functional group to DNA-targeted drug design.     

Spectrophotometric Study on the Binding of Two Water Soluble Schiff Base Complexes of Mn (III) with ct-DNA

In this work, binding of two water soluble Schiff base complexes: Bis sodium (5-sulfosalicylaldehyde) o- phenylendiiminato) Manganese (III) acetate (Salophen complex) and Bis sodium (5-sulfosalicylaldehyde) 1, 2 ethylendiiminato) Manganese (III) acetate (Salen complex) with calf thymus (ct) DNA were investigated by using different spectroscopic and electrometric techniques including UV-vis, Circular dichroism (CD) and fluorescence spectroscopy, viscommetry and cyclic voltammetry (CV). Both complexes have shown a hyperchromic and a small bathochromic shift in the visible region spectra. A competitive binding study showed that the enhanced emission intensity of ethidium bromide (EB) in the presence of DNA was quenched by the addition of the two Schiff base complexes indicating that they displace EB from its binding site in DNA. Moreover structural changes in the CD spectra and an increase in the CV spectra with addition of DNA were observed. The results show that both complexes bind to DNA. The binding constants have been calculated using fluorescence data for two complexes also K_b was calculated with fluorescence Scatchard plot for Salophen. Ultimately, the experimental results show that the dominant interactions are electrostatic while binding mode is surface binding then followed by hydrophobic interactions in grooves in high concentration of complexes.     

STUDIES ON COPPER-CONTAINING NAD GLYCOHYDROLASE FROM AGKISTRODON ACUTUS VENOM BY FLUORESCENCE AND CD SPECTROSCOPY

ABSTRACT

The properties of NAD Glycohydrolase (NADase), purified from Agkistrodon acutus venom, have been studied by fluorescence and CD spectroscopy. The fluorescence intensities of NADase decrease by about 1% or 3% when the concentrations of I^? ion are 0.1 mol/L or 0.2 mol/L in the NADase solutions, respectively. However, the fluorescence intensities of the NADase are quenched by about 25% and 48%, respectively, with further addition of 1 mmol/L EDTA into solutions. CD spectra also suggested that EDTA could remove Cu²⁺ ion from NADase molecule and the conformation of NADase changed much. So Cu²⁺ ion is very important to maintain the geometrical structure of NADase.     

Synthesis,Characterization and DNA Interaction Study of a New Oxovanadium (IV) Complex Containing Acetylacetone and Dicyandiamide as Ligands

ABSTRACT

A new oxovanadium (IV) complex [VO(acac)₂DCDA]H₂O (where acac = acetylacetonate; DCDA = dicyandiamide) was synthesized and characterized by elemental analysis, IR, UV, ESR, TG-DTA analysis and powdered XRD. The electronic and ESR spectral studies indicate the monomeric nature of the complex having distorted octahedral structure. The complex shows prominent emission peak at 485 nm and excitation peak at 355 nm. The cyclic voltammetry study shows irreversible process. DNA binding study of the complex with CT-DNA indicates nonintercalative mode with binding constant 2.063 × 10² M^?1.     

Study on the toxic interactions of Ni with DNA using neutral red dye as a fluorescence probe

The interaction between Ni²⁺ and calf thymus DNA (ctDNA) was investigated in simulated physiological buffer (pH 7.4) using the Neutral Red (NR) dye as a spectral probe by UV-vis absorption and fluorescence spectroscopy, as well as CD spectra. The experimental results showed that the conformational changes in DNA helix induced by Ni²⁺ are the reason for the fluorescence quenching of the DNA-NR system. From the experimental results, conclusion can be drawn that Ni²⁺ can cause structural changes of ctDNA and bind with DNA by electrostatic interaction. At the same time, the paper proved that conformation changes of DNA can also lead to the fluorescence decrease of DNA-probe systems.     

Toxic effects of copper (II) ions on bovine hemoglobin

In this paper, the toxic influence of copper ions (II) on bovine hemoglobin was investigated by the combination of ultraviolet-visible absorption, fluorescence, time-resolved fluorescence, synchronous fluorescence, and circular dichroism spectra. Driven by hydrophobic and electrostatic forces, copper ions (II) could interact with bovine hemoglobin to form bovine hemoglobin-copper ions (II) complex with one binding site. The binding constant (K) was 1.57?×?10⁴, 1.89?×?10⁴ and 2.11?×?10⁴?L/mol at 298, 304, and 310?K, respectively. The binding distance (r) was 4.24?nm. Fluorescence and time-resolved fluorescence spectra showed that bovine hemoglobin quenched by copper ions (II) was a static quenching process. Results of synchronous fluorescence spectra revealed that the microenvironment and the conformation of bovine hemoglobin were changed during the binding reaction. Data of circular dichroism spectra suggested that with the increasing concentration of copper ions (II), the secondary structure of bovine hemoglobin underwent a decrease in α-helix and alteration in backbone microenvironment. Copper ions (II) was thus evidenced to have a certain toxic effect on physical bodies.     

Spectroscopic study on the interaction of eugenol with salmon sperm DNA in vitro

Fluorescence spectra, absorption spectra, melting temperature, ionic strength effect, and viscosity experiments were described that characterize the interaction of eugenol with salmon sperm DNA in vitro. Eugenol was found to bind but weakly to DNA, with binding constants of 4.23×10³, 3.62×10³ and 2.47×10³ L mol^?1 at 18, 28 and 38 °C respectively. The Stern–Volmer plots at different temperatures suggested that the quenching type of fluorescence of eugenol by DNA was a static quenching. Both the relative viscosity and the melting temperature of DNA were increased by the addition of eugenol. The changes of ionic strength had no affect on the binding. In addition, the binding constant of eugenol with single stranded DNA (ssDNA) was larger than that of eugenol with double stranded DNA (dsDNA). These results revealed that the binding mode of eugenol to DNA was intercalative binding. The thermodynamic parameters ΔH, ΔG and ΔS were also obtained according to the Van't Hoff equations, which suggested that hydrogen bond or van der Waals force might play an important role in a binding of eugenol to DNA. Based on the theory of the Förster energy transference, the binding distance between DNA and eugenol was determined as 4.40 nm, indicating that the static fluorescence quenching of eugenol by DNA was also a non-radiation energy transfer process.     

Studies on the Binding of Barbaloin to Human Gamma Globulin

The binding of barbaloin to human gamma globulin (HGG) was studied in vitro under simulated physiological conditions by spectroscopic method including circular dichroism (CD), Fourier transformation infrared (FT‐IR) spectroscopy and fluorescence spectroscopy. The binding parameters of HGG to barbaloin were studied from the fluorescence decrease of HGG by the fluorometric titrations in the presence of barbaloin. The Sips plots indicated that the binding of HGG to barbaloin at 296, 304, 310, and 317 K was characteristic of two binding sites with the average affinity constant K _o at 1.152×10⁴, 1.022 ×10⁴, 0.9618×10⁴, and 0.8937×10⁴, respectively. The binding process was exothermic, spontaneous, and entropy driven, as indicated by the thermodynamic analyses, and the major part of binding energy was electrostatic interaction. The secondary structure elements of free HGG and its barbaloin complexes were estimated by the FT‐IR spectra and the curve‐fitted results of amide I band, which were in agreement with the analyses of CD spectra. Furthermore, the average binding distance between the donor and the acceptor (3.74 nm) was obtained on the basis of the theory of Förster energy transfer.     

Synthesis, Crystal Structure, DNA-binding Properties and Cytotoxic Activity of the Copper (II) Complex Involving Xanthone

1, 8-(3, 6, 9-Trioxaundecane-1, 11-diyldioxy)xanthone (L), and its new Cu (II) complex [Cu·L·(CH₃CN)₂](ClO₄)₂ have been synthesized and characterized by ¹H NMR, electrospray mass spectra (ESI-MS), elemental analyses, infrared spectra (IR) and X-ray single crystal diffraction. The crystal structure of complex shows that Cu (II) ion is encapsulated within the macrocycle of L. The geometry around copper is a distorted square bipyramid with two acetonitrile molecules at axial position, and four macrocyclic oxygens including the carbonyl oxygen on the equatorial positions. The interaction of Cu (II) complex with calf thymus DNA (ct DNA) has been investigated by spectrophotometric titrations, ethidium bromide (EB) displacement experiments, circular dichroism (CD) spectra and viscosity measurements. Rresults indicate that Cu (II) complex can intercalate into the DNA base pairs by the plane of xanthone ring. Furthermore, the Cu (II) complex was tested against tumor cell lines including ECA109, SGC7901and GLC-82 by MTT (microculture tetrazolium) method. The studies of DNA-binding agree with the effects on the inhibition of tumor cells in vitro.     

Study on the Interaction between Florasulam and Bovine Serum Albumin

In this paper, the interaction between florasulam (FU, 2′,6′,8-trifluoro-5-methoxy [Kragh-Hansen U, Molecular aspects of ligand binding to serum albumin. Pharmacol Rev 33(1):17–53 1981; Carter DC and Ho JX, Structure of serum albumin. Adv Protein Chem 45:153–203 1994; He XM, and Carter DC, Atomic structure and chemistry of human serum albumin. Nature 358(6383):209–215 1992] triazolo [1,5-c]pyrimidine-2-sulfonanilide) and bovine serum albumin (BSA) was investigated by fluorescence, ultraviolet absorption (UV) and Far-UV circular dichroism (CD) spectrometries. A strong fluorescence quenching was observed and the quenching mechanism was considered as static quenching. The binding constant of FU with BSA at 299 and 309 K were obtained as 1.5?×?10⁴ and 7.1?×?10³ l mol^?1, respectively. There was one binding site between FU and BSA. The thermodynamic parameters enthalpy change (ΔH) and entropy change (ΔS) were calculated as ?57.89 kJ mol^?1 and ?113.6 J mol^?1 K^?1, respectively, which indicated that the acting force between FU and BSA was mainly hydrogen bond and Van der Waals force. According to the Förster non-radiation energy transfer theory, the average binding distance between donor (BSA) and acceptor (FU) was obtained (r?=?1.59 nm). The investigations of the UV/Vis and CD spectra of the system showed that the conformation of BSA was changed in presence of FU.     

Investigation of L(+)-Ascorbic acid with Raman spectroscopy in visible and UV light

Abstract: Raman spectroscopy investigations of l(+)-ascorbic acid and its mono- and di-deprotonated anions (AH^? and A^2?) are reviewed and new measurements reported with several wavelengths, 229, 244, 266, 488, and 532 nm. Results are interpreted, assisted by new DFT/B3LYP quantum chemical calculations with 6-311++G(d,p) basis sets for several conformations of ascorbic acid and the anions. Raman spectra were measured during titration with NaOH base in an oxygen-poor environment to avoid fluorescence when solutions were alkaline. The ultraviolet (UV) absorption band for ascorbic acid in aqueous solution at ～247 nm was found to cause strong resonance enhancement for the ring C?C stretching mode (called B) at ～1692 cm^?1. The ascorbate mono-anion absorbs at ～264.8 nm giving Raman resonance enhancement for the same ring C–C bond stretching, downshifted to ～1591 cm^?1. Finally, for the ascorbate di-anion, absorption was found at ～298.4 nm with molar absorptivity of ～7,000 L mol^?1 cm^?1 and below ～220 nm. With UV light (244 and 266 nm), strongly basic solutions gave pronounced Raman resonance enhancement at ～1556 cm^?1. Relatively weak preresonance enhancement was seen for A^2? when excitation was done with 229 nm UV light, allowing water bands to become observable as for normal visible light Raman spectra.     

Novel Multicolor Schiff Base Polymers Prepared via Oxidative Polycondensation

A series of diimine Schiff bases and their polymers were synthesized via the oxidative polycondensation reaction. The structures of the compounds were confirmed by ¹H-NMR, ¹³C-NMR, FT-IR and UV–vis spectral measurements. Electrochemical and optical band gap values of synthesized compounds were determined by cyclic voltammetry (CV) and UV–vis measurements, respectively. Fluorescence measurements of the compounds were conducted in various solvents. The effects of solution concentration on the fluorescence spectra were investigated and quantum yield was calculated for the polymer of 5-(diethylamino)-2-(biphenylmethylene) hydrazonomethylphenol (PDEAHP). According to fluorescence measurements, the quantum yield of PDEAHP was found as 16 % in DMF solution. Thermal characteristics of polymers were studied by TG-DTA and DSC analyses.     

Spectroscopic Determination of Cysteine with Alizarin Red S and Copper

ABSTRACT

The interaction between metal complex Cu²⁺–ARS (Alizarin Red S) and l-cysteine was investigated via fluorescence and absorption spectroscopies. In pH 5.2 Britton–Robinson buffer, the addition of L-cysteine into Cu²⁺–ARS system resulted in a fluorescence enhancement because cysteine reduced Cu²⁺ to Cu⁺, which led to Cu²⁺–ARS decompound, and ARS was released. The result was also supported by absorption spectroscopy change. A good linear response of fluorescence intensity as a function of cysteine concentration was obtained ranging from 1.0 × 10^?6 to 4.0 × 10^?5 mol L^?1 with the detection limit as 1.08 × 10^?7 mol L^?1. The introduced method has high selectivity over other amino acids such as cystine, tyrosine, tryptophan, methionine, and glycine. It was applied to determine cysteine in protein hydrolysate of fresh pig blood with recovery of 88.4–100.2%.     

Synthesis of Fluorescent Gold Nanoclusters Directed by Bovine Serum Albumin and Application for Nitrite Detection

In the present work, gold nanocluster (GNC) induced by bovine serum albumin (BSA) was synthesized as a novel fluorescence probe to detect nitrite (NO₂ ^?) sensitively and selectively. The fluorescence of GNC was found to be quenched effectively by NO₂ ^?. Under the optimum conditions, it was found that the change of fluorescence intensity was proportional with the concentration of NO₂ ^? in the linear range of 0.1–50 μM (R?=?0.9990), with a detection limit (S/N?=?3) of 30 nM. The absorption spectroscopy, circular dichroism (CD), and X-ray photoelectron spectroscopy (XPS) studies were employed to discuss the quenching mechanism. In addition, the present approach was successfully applied in real water samples.     

Highly sensitive and selective fluorescent “turn-on” probe for determination of aluminum ion in aqueous solution

ABSTRACT

A novel fluorescent sensor, 1-((2-hydroxynaphthalen-1-yl)methylene) semicarbazide, was synthesized and characterized by infrared spectra, elemental analysis, electrospray ionization mass spectra. The fluorescent sensing behaviors of the sensor toward different metals ions, anions, and amino acids were determined by UV–vis and fluorescence spectroscopy. The fluorescent sensor exhibited obvious changes in its electronic and fluorescent spectral behavior in the visible region of the spectrum in the presence of aluminum ion with the lower detection limit was 8.9 × 10^?9 M.