Low‐Background,Highly Sensitive DNA Biosensor by Using an Electrically Neutral Cobalt(II) Complex as the Redox Hybridization Indicator

An electrically neutral cobalt complex, [Co(GA)₂(phen)] (GA=glycollic acid, phen=1,10‐phenathroline), was synthesized and its interactions with double‐stranded DNA (dsDNA) were studied by using electrochemical methods on a glassy carbon electrode (GCE). We found that [Co(GA)₂(phen)] could intercalate into the DNA duplex through the planar phen ligand with a high binding constant of 6.2(±0.2)×10⁵ M ^?1. Surface studies showed that the cobalt complex could electrochemically accumulate within the modified dsDNA layer, rather than within the single‐stranded DNA (ssDNA) layer. Based on this feature, the complex was applied as a redox‐active hybridization indicator to detect 18‐base oligonucleotides from the CaMV35S promoter gene. This biosensor presented a very low background signal during hybridization detection and could realize the detection over a wide kinetic range from 1.0×10^?14 M to 1.0×10^?8 M , with a low detection limit of 2.0 fM towards the target sequences. The hybridization selectivity experiments further revealed that the complementary sequence, the one‐base‐mismatched sequence, and the non‐complementary sequence could be well‐distinguished by the cobalt‐complex‐based biosensor.     

多吡啶锌配合物键合与切割DNA研究

The complex of Zn[(phen)(dione)Cl]ClO_4·H_2O(where phen is 1,10-phenanthroline and dione is 1,10-phenan-throline-5,6-dione)has been synthesized and characterized.The interaction of the complex with DNA was investi-gated using UV absorption,fluorescence spectroscopy and electrophoresis measurements.The results show that thecomplex mainly binds to the double helix of DNA with intercalation mode and the binding constant K is 2.4×10~4mol~(-1)·L.Moreover,the complex can efficiently cleave plasmid DNA at physiological pH and temperature.Thecleavage occurs via a hydrolysis mechanism,which is showed by adding radical scavengers,rigorously anaerobicexperiments,analysis for malondialdehyde-like products,and the hydrolysis experiment of BDNPP with a rate con-stant k_(obs)of 5.3×10~(-6)s~(-1).     

DNA Binding Studies and Cytotoxicity of a Dinuclear Pt(II) Diazapyrenium-Based Metallo-supramolecular Rectangular Box

The interaction with native DNA of a 2,7-diazapyrenium-based ligand 1 and its Pt(II) rectangular metallacycle 2 is explored through circular and linear dichroism and fluorescence spectroscopies. The metal-free ligand 1 binds through intercalation, with a binding constant of approximately 5×10(5) M(-1) , whereas the metallacycle 2 binds and bends the DNA with a binding constant of 7×10(6) M(-1) . PCR assays show that metallo-supramolecular box 2 interferes with DNA transactions in vitro whereas the intercalator 1 does not. The metallacycle is active against four human cancer cell lines, with IC(50) values ranging between 3.1 and 19.2?μM and shows similar levels of efficacy, but a different spectrum of activity, to cisplatin.     

Electrochemical Studies of the Interaction of 2‐Nitroacridone with DNA and Determination of DNA

A new acridone derivate 2‐nitroacridone (NAD) was synthesized and a new method of electrochemical probe has been proposed for the determination of salmon sperm DNA based on its interaction with NAD. The electrochemical behavior of interaction of NAD with DNA was investigated on glassy carbon electrode (GCE). In the presence of DNA, the peak current of NAD decreases and the peak potential shifts to a more positive potential without appearance of a new peak. The binding ratio between NAD and salmon sperm DNA was calculated to be 2 : 1 and the binding constant was 3.19×10⁵ L/mol. The decrease of the peak current (ΔI_p) of NAD was proportional to the concentration of DNA in the range from 1.55×10^?7 M to 2.02×10^?6 M with the detection limit of 3.10×10^?8 M, and DNA of synthetic sample was determined satisfactorily. Additionally, the binding mechanism was preliminarily discussed. The mode of interaction between NAD and DNA was found to be intercalation binding.     

Biointeraction analysis of carbamazepine binding to α1‐acid glycoprotein by high‐performance affinity chromatography

Interactions of the drug carbamazepine with the serum protein α₁‐acid glycoprotein (AGP) were examined by high‐performance affinity chromatography. Frontal analysis studies with an immobilized AGP column and control column indicated carbamazepine had both low‐affinity interactions with the support and high‐affinity interactions with AGP. When a correction was made for binding to the support, the association equilibrium constant measured at pH 7.4 and 37°C for carbamazepine with AGP was 1.0 (±0.1)×10⁵ M^?1, with values that ranged from 5.1 to 0.58×10⁵ M^?1 in going from 5 to 45°C. It was found in competition studies that these interactions were occurring at the same site that binds propranolol on AGP. Temperature studies indicated that the change in enthalpy was the main driving force for the binding of carbamazepine to AGP. These results provide a more complete picture of how carbamazepine binds to AGP in serum. This report also illustrates how high‐performance affinity chromatography can be used to examine biological interactions and drug–protein binding in situations in which significant interactions for an analyte are present with both the chromatographic support and an immobilized ligand.     

Studies on the nuclease activity and interactions of the mixed‐polypyridyl [Ni2(1,3‐tpbd)(diimine)2(H2O)2]4+ complexes with thioredoxin reductase

Three new nickel(II) complexes formulated as [Ni₂(1,3‐tpbd)(diimine)₂(H₂O)₂]⁴⁺ [1,3‐tpbd = N,N,N′,N′‐tetrakis(2‐pyridylmethyl)benzene‐1,3‐diamine, where diimine is an N,N‐donor heterocyclic base like 1,10‐phenanthroline (phen),2,2′‐bipyridine (bpy), 4,5‐diazafluoren‐9‐one (dafo)], have been synthesized and structurally characterized by X‐ray crystallography: [Ni₂(1,3‐tpbd)(phen)₂(H₂O)₂]⁴⁺ (1), [Ni₂(1,3‐tpbd)(bpy)₂(H₂O)₂]⁴⁺(2) and [Ni₂(1,3‐tpbd)(dafo)₂(H₂O)₂]⁴⁺ (3). Single‐crystal diffraction reveals that the metal atoms in the complexes are all in a distorted octahedral geometry and in a trans arrangement around 1,3‐tpbd ligand. The interactions of the three complexes with calf thymus DNA (CT‐DNA) have been investigated by UV absorption, fluorescence spectroscopy, circular dichroism and viscosity. The apparent binding constant (K_app) values are calculated to be 1.91 × 10⁵ m ^?1 for 1, 1.18 × 10⁵ m ^?1 for 2, and 1.35 × 10⁵ m ^?1 for 3, following the order 1 > 3 > 2. The higher DNA binding affinity of 1 is due to the involvement in partial insertion of the phen ring between the DNA base pairs. A decrease in relative viscosities of DNA upon binding to 1–3 is consistent with the DNA binding affinities. These complexes efficiently display oxidative cleavage of supercoiled DNA in the presence of H₂O₂ (250 µ m ), with 3 exhibiting the highest nuclease activity. The rate constants for the conversion of supercoiled to nicked DNA are 5.28 × 10^?5 s^?1 (for 1), 6.67 × 10^?5 s^?1 (for 2) and 1.39 × 10^?4 s^?1 (for 3), also indicating that complex 3 shows higher catalytic activity than 1 and 2. Here the nuclease activity is not readily correlated to binding affinity. The inhibitory effect of complexes 1–3 on thioredoxin reductase has also been examined. The IC₅₀ values are calculated to be 26.54 ± 0.57, 31.03 ± 3.33 and 8.69 ± 2.54 µ m , respectively, showing a more marked inhibitory effect on thioredoxin reductase by complex 3 than the other two complexes. Copyright © 2012 John Wiley & Sons, Ltd.     

Three Arene‐Ru(II) compounds of 2‐halogen‐5‐aminopyridine: Synthesis,characterization, and cytotoxicity

Three novel compounds, (η⁶‐p‐cymene)RuCl₂(2‐fluoro‐5‐aminopyridine) (compound 1), (η⁶‐p‐cymene)RuCl₂(5‐amino‐2‐chlorpyridine) (compound 2) and (η⁶‐p‐cymene)RuCl₂(2‐bromo‐ 5‐aminopyridine) (compound 3), were synthesized and characterized. The compound 1 and 3 were determined by X‐ray diffraction, showing a distorted piano‐stool type of geometry with similar bond lengths and angles around the ruthenium. Compound 2 exhibited moderate in vitro activity against A549 and MCF‐7 human cancer cells, the other two lower activities. The UV–vis and fluorescent absorption titrations showed that three compounds binded with CT‐DNA in a minor groove. The intrinsic binding constants (Kb) were calculated to be 2.13(±0.03) × 10⁵ M^?1, 2.89(±0.03) × 10⁵ M^?1 and 2.45(±0.03) × 10⁵ M^?1 for compound 1, 2 and 3, respectively, by using UV–vis absorption titrations data. Among the three compound, the highest value of intrinsic binding constant of compound 2 was consistent with its highest cytoxicity against A549 and MCF‐7 human cancer cells in vitro.     

Kinetic Study of Peroxidase‐Catalyzed Coupling of Benzene‐1,4‐diamine and N‐(2‐Aminoethyl)naphthalen‐1‐amine: Development of Micromolar Hydrogen Peroxide Reaction System

A novel chromogenic method to measure the peroxidase activity using para‐phenylenediamine dihydrochloride (=benzene‐1,4‐diamine hydrochloride; PPDD) and N‐(1‐naphthyl)ethylenediamine dihydrochloride (=N‐(2‐aminoethyl)naphthalen‐1‐amine; NEDA) is presented. The PPDD entraps the free radical and gets oxidized to electrophilic diimine, which couples with NEDA to give an intense red‐colored chromogenic species with maximum absorbance at 490 nm. This assay was adopted for the quantification of H₂O₂ between 20 and 160 μM . Catalytic efficiency and catalytic power of the commercial peroxidase were found to be 4.47×10⁴ M ^?1 min^?1 and 3.38×10^?4 min^?1, respectively. The catalytic constant (k_cat) and specificity constant (k_cat/K_m) at saturated concentration of the co‐substrates were 0.0245×10³ min^?1 and 0.0445 μM ^?1 min^?1, respectively. The chromogenic coupling reaction has a minimum interference from the reducing substances such as ascorbic acid, L ‐cystein, citric acid, and oxalic acid. The method being simple, rapid, precise, and sensitive, its applicability has been tested in the crude vegetable extracts that showed peroxidase activity.     

Regulation of α‐Chymotrypsin Catalysis by Ferric Porphyrins and Cyclodextrins

Positively charged α‐chymotrypsin (ChT) formed a 1:1 complex with negatively charged 5,10,15,20‐tetrakis(4‐sulfonatophenyl)porphyrinato iron(III) (FeTPPS) in phosphate buffer at pH 7.4 through electrostatic interaction. In spite of the large binding constant (K=4.8×10⁵ M ^?1), FeTPPS could not completely inhibit the catalysis of ChT in the hydrolysis of the model substrate, N‐succinyl‐L ‐phenylalanine p‐nitroanilide (SPNA). The degree of inhibition (60 %) was saturated at 1.6 equivalents of FeTPPS, which indicates that covering of the active site of ChT by FeTPPS was insufficient. The enzymatic activity lowered by FeTPPS was entirely recovered for the freshly prepared sample when the porphyrin on the protein surface was detached by per‐O‐methylated β‐cyclodextrin (TMe‐β‐CD), which formed a stable 1:2 inclusion complex with FeTPPS (K₁=1.26×10⁶ M ^?1, K₂=6.3×10⁴ M ^?1). FeTPPS gradually induced irreversible denaturation of ChT, and the denatured ChT further lost its catalytic ability. No repairing effect of TMe‐β‐CD was observed with irreversibly denatured ChT. A new reversible inhibitor, 5,10,15,20‐tetrakis[4‐(3,5‐dicarboxyphenylmethoxy)phenyl]porphyrinato iron(III) (FeP8M), was then designed, and its inhibitory behavior was examined. FeP8M formed very stable 1:1 and 1:2 FeP8M/ChT complexes with ChT, the K₁ and K₂ values being 2.0×10⁸ and 1.0×10⁶ M ^?1, respectively. FeP8M effectively inhibited the ChT‐catalyzed hydrolysis of SPNA (maximum degree of inhibition=85 %), and the activity of ChT was recovered by per‐O‐methylated γ‐cyclodextrin. No irreversible denaturation of ChT occurred upon binding with FeP8M. The kinetic data support the observation that, for nonincubated samples, both inhibitors did not cause significant conformational change in ChT and inhibited the ChT activity by covering the active site of the enzyme.     

Synthesis,spectroscopy, thermal and biological aspect of novel six‐coordinated dimeric iron(III) mixed‐ligand complexes

The mixed‐ligand complexes of iron(III) with 1‐cyclopropyl‐6‐fluoro‐4‐oxo‐7‐piperazin‐1‐yl‐1,4‐dihydroquinoline‐3‐carboxylic acid and various neutral bidentate Schiff base ligands were prepared. The structure of mixed‐ligand complexes was investigated using spectral, physicochemical and elemental analyses. Biocidal activity was determined using agar plate technique against Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Salmonella typhi, Escherichia coli and Serratia marcescens . The result showed a significant increase in a biocidal activity compared with parent ligands, metal salts and standard drugs (ofloxacin, levofloxacin). DNA binding and cleavage studies were carried out using absorption titration and gel electrophoresis techniques, respectively. The binding constant of Fe(III) complexes was obtained in the range 2.5–4.0 × 10⁴ M ^?1. The DNA binding and cleavage efficacy were raised in mixed‐ligand complexes as compared with parental ligands and metal salts. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis,structural characterization and DNA-binding studies of a new cobalt (II) complex: (HAcr)<Subscript>4</Subscript>[Co(Sal)<Subscript>3</Subscript>]

A new cobalt (II) coordination compound was synthesized using proton transfer mechanism. The reaction between CoCl₂·2H₂O, Salicylic acid (H₂Sal) and acridine (Acr) gave a new coordination compound formulated as (HAcr)₄[Co(Sal)₃], which was characterized by elemental analysis, NMR, IR and UV/Vis spectroscopies. The interaction of this complex with DNA has been investigated in vitro using UV absorption, fluorescence spectroscopy, viscosity measurements and gel electrophoresis methods. The intrinsic binding constant has been estimated to be 5.8 × 10⁵ M^?1 using UV absorption. The interaction of DNA–Co (II) complex caused quenching in fluorescence. The binding constant, the number of binding site and Stern–Volmer quenching constant have been calculated to be 7.7 × 10⁴ M^?1, 1.143 and 1.5 × 10⁴ Lmol^?1, respectively. The increase in the viscosity of DNA with increasing the concentration of the Co (II) complex and the observations of other experiments suggest that the cobalt (II) complex binds to DNA by partial intercalation binding mode. Furthermore, the interaction of DNA–Co (II) complex was confirmed using gel electrophoresis studies. Moreover, molecular docking technique predicted partial intercalation binding mode for the complex.     

Synthesis,DNA binding,nuclease activity and cytotoxic studies of a wheel‐shaped octanuclear copper(II) complex based on 1,2,4‐triazole

The antitumor activity shown by many platinum complexes has produced a strong interest in research of new organometallic compounds. Among the metal compounds synthesized and tested, copper compounds have received considerable attention because of their cytotoxic activity against solid tumors. A novel wheel‐shaped octanuclear copper(II) complex with a 1,2,4‐triazole derivative ligand formulated as [Cu₈L₄](ClO₄)₈?11H₂O ( 1 ) (L = 3,5‐bis((bis(2‐hydroxylethyl)amino)methyl)‐4 H‐1,2,4,‐triazole‐4‐amine) has been synthesized and structurally characterized. In 1 , eight Cu atoms are linked through 1,2,4‐triazole units and alkoxide bridges to form a centrosymmetric octanuclear Cu(II) metallomacrocycle. The interaction of complex 1 with calf thymus DNA has been studied using UV absorption, fluorescence and circular dichroism spectroscopies, viscosity measurements and cyclic voltammetry. The apparent binding constant (k_app) value for 1 is 1.59 × 10⁵ M^?1. Furthermore, complex 1 displays efficient oxidative cleavage of supercoiled DNA in the presence of external agents, the rate constant for the conversion of supercoiled to nicked DNA being 2.67 × 10^?5 s^?1. Interestingly, cytotoxicity studies on the MCF‐7 human breast cancer cell line show that the IC₅₀ value of 1 is less than that of cisplatin for the same cell line, revealing that it has the potential to act as an effective metal‐based anticancer drug. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and characterization of water‐soluble copper(II), cobalt(II) and zinc(II) complexes derived from 8‐hydroxyquinoline‐5‐sulphonic acid: DNA binding and cleavage studies

Three water‐soluble complexes, [Cu₂L₂Cl₂] ( 1 ), [CoL₂(im)₂] ( 2 ) and [ZnLClH₂O] ( 3 ) (HL = 8‐hydroxyquinoline‐5‐sulphonic acid; im = N ‐methylimidazole), were prepared and characterized using various spectral techniques. The DNA binding behaviour of complexes 1 – 3 was studied using UV–visible and circular dichroism (CD) spectra and cyclic voltammetry. All three complexes exhibit hypochromism but complexes 1 and 3 alone give a red shift of 4 nm with a significant binding constant of K _b = 2.1 × 10⁴ and 1.0 × 10⁴ M⁻¹, respectively, but complex 2 shows no red shift with lower K _b of 4.1 × 10³ M⁻¹. The voltammetric E _1/2 of complex 1 on interaction with herring sperm DNA shifts to a more positive potential, as expected, than complex 2 due to higher DNA affinity. Additionally, analysis of electrochemical data yields a value of K ₊/K ₂₊ greater than one suggesting that complex 1 binds to DNA through intercalation in the M(I) state. Evidently in CD spectral analysis, complex 1 exhibits a decrease in molar ellipticity with a red shift of 10 nm and a significant decrease in intensity compared to complexes 2 and 3 . This clearly indicates that complex 1 induces the B → A transition to a greater extent than 2 and 3 . Oxidative cleavage using circular plasmid pUC18 DNA with complex 1 was investigated using gel electrophoresis. Interestingly, complex 1 displays a strong DNA binding affinity and is efficient in cleaving DNA in the presence of H₂O₂ at pH = 8.0 at 37 °C.     

Halide‐Anion Binding by Singly and Doubly N‐Confused Porphyrins

The halide‐binding properties of N‐confused porphyrin (NCP, 1 ) and doubly N‐confused porphyrins (trans‐N₂CP ( 2 ), cis‐N₂CP ( 3 )) were examined in CH₂Cl₂. In the free‐base forms, cis‐N₂CP ( 3 ) showed the highest affinity to each anion (Cl^?, Br^?, I^?) with association constants K_a=7.8×10³, 1.9×10³, and 5.8×10² M ^?1, respectively. As metal complexes, on the other hand, trans‐N₂CP 2–Cu exhibited the highest affinity to Cl^?, Br^?, and I^? with K_a=9.0×10⁴, 2.7×10⁴, and 1.9×10³ M ^?1, respectively. The corresponding K_a values for cis‐N₂CP 3–Cu and NCP 1–Cu were about 1/10 and 1/2, respectively, of those of 2–Cu . With the help of density functional theory (DFT) calculations and complementary affinity measurements of a series of trisubstituted N‐confused porphyrins, the efficient anion binding of NCPs was attributed to strong hydrogen bonding at the highly polarized NH moieties owing to the electron‐deficient C₆F₅ groups at meso positions as well as the ideally oriented dipole moments and large molecular polarizability. The orientation and magnitude of the dipole moments in NCPs were suggested to be important factors in the differentiation of the affinity for anions.     

Binding of Scandium Ions to Metalloporphyrin–Flavin Complexes for Long‐Lived Charge Separation

A porphyrin–flavin‐linked dyad and its zinc and palladium complexes (MPor?Fl: 2 ?M, M=2 H, Zn, and Pd) were newly synthesized and the X‐ray crystal structure of 2 ?Pd was determined. The photodynamics of 2 ?M were examined by femto‐ and nanosecond laser flash photolysis measurements. Photoinduced electron transfer (ET) in 2 ?H₂ occurred from the singlet excited state of the porphyrin moiety (H₂Por) to the flavin (Fl) moiety to produce the singlet charge‐separated (CS) state ¹(H₂Por^.+?Fl^.?), which decayed through back ET (BET) to form ³[H₂Por]*?Fl with rate constants of 1.2×10¹⁰ and 1.2×10⁹ s^?1, respectively. Similarly, photoinduced ET in 2 ?Pd afforded the singlet CS state, which decayed through BET to form ³[PdPor]*?Fl with rate constants of 2.1×10¹¹ and 6.0×10¹⁰ s^?1, respectively. The rate constant of photoinduced ET and BET of 2 ?M were related to the ET and BET driving forces by using the Marcus theory of ET. One and two Sc³⁺ ions bind to the flavin moiety to form the Fl?Sc³⁺ and Fl?(Sc³⁺)₂ complexes with binding constants of K₁=2.2×10⁵ M ^?1 and K₂=1.8×10³ M ^?1, respectively. Other metal ions, such as Y³⁺, Zn²⁺, and Mg²⁺, form only 1:1 complexes with flavin. In contrast to 2 ?M and the 1:1 complexes with metal ions, which afforded the short‐lived singlet CS state, photoinduced ET in 2 ?Pd???Sc³⁺ complexes afforded the triplet CS state (³[PdPor^.+?Fl^.??(Sc³⁺)₂]), which exhibited a remarkably long lifetime of τ=110 ms (k_BET=9.1 s^?1).     

Molecular‐Recognition‐Assisted pKa Shifts and Metal‐Ion‐Induced Fluorescence Regeneration in p‐Sulfonatocalix[6]arene‐Encapsulated Acridine

The host–guest interactions of cationic (AcH⁺) and neutral (Ac) forms of the dye acridine with the macrocyclic host p‐sulfonatocalix[6]arene (SCX6) were investigated by using ground‐state absorption, steady‐state and time‐resolved fluorescence, and NMR measurements. The cationic form undergoes significant complexation with SCX6 (K_eq=2.5×10⁴ M ^?1), causing a sharp decrease in the fluorescence intensity and severe quenching in the excited‐state lifetime of the dye. The strong binding of the AcH⁺ form of the dye with SCX6 is attributed to ion–ion interactions involving the sulfonato groups (SO₃^?) of SCX6 and the positively charged AcH⁺ at pH of approximately 4.3. Whereas, the neutral Ac form of the dye undergoes weak complexation with SCX6 (K_eq=0.9×10³ M ^?1) and the binding constant is lowered by one order of magnitude compared with that of the SCX6–AcH⁺ system. The strong affinity of SCX6 to the protonated form leads to a large upward pK_a shift (≈2 units) in the dye. In contrast, strong emission quenching upon SCX6 interaction and the regeneration of fluorescence intensity of the dye in the presence of Gd³⁺ through competitive binding have also been demonstrated.     

Experimental and Theoretical Studies on DNA‐Binding and Spectral Properties of ‘Light Switch’ Complexes [Ru(L)2(ppn)]2+ (L=2,2′‐Bipyridine and 1,10‐Phenanthroline; ppn=Pteridino[6,7‐f] [1,10]phenanthroline‐11,13‐diamine)

The ligand pteridino[6,7‐f] [1,10]phenanthroline‐11,13‐diamine (ppn) and its Ru^II complexes [Ru(bpy)₂(ppn)]²⁺ ( 1 ; bpy=2,2′‐bipyridine) and [Ru(phen)₂(ppn)]²⁺ ( 2 ; phen=1,10‐phenanthroline) were synthesized and characterized by elemental analysis, electrospray MS, ¹H‐NMR, and cyclic voltammetry. The DNA‐binding behaviors of 1 and 2 were studied by spectroscopic and viscosity measurements. The results indicate that both complexes strongly bind to calf‐thymus DNA in an intercalative mode, with DNA‐binding constants K_b of (1.7±0.4)?10⁶ M ^?1 and (2.6±0.2)?10⁶ M ^?1, respectively. The complexes 1 and 2 exhibit excellent DNA‐‘light switch’ performances, i.e., they do not (or extremely weakly) show luminescence in aqueous solution at room temperature but are strongly luminescent in the presence of DNA. In particular, the experimental results suggest that the ancillary ligands bpy and phen not only have a significant effect on the DNA‐binding affinities of 1 and 2 but also have a certain effect on their spectral properties. [Ru(phen)₂(ppn)]²⁺( 2 ) might be developed into a very prospective DNA‐‘light switch’ complex. To explain the DNA‐binding and spectral properties of 1 and 2 , theoretical calculations were also carried out applying the DFT/TDDFT method.     

Polymeric Copper(II) Paddlewheel Carboxylate: Structural Description,Electrochemistry, and DNA‐binding Studies

A polymeric complex of copper(II) was isolated and purified from the self‐assembly of CuSO₄ and 2‐phenyl acetate in aqueous medium. It was characterized through FT‐IR, UV/Vis, electron spin resonance, electrochemical solution studies, and powder and single crystal XRD techniques. The structure was revealed to consist of directly interconnected dimeric paddlewheel building units without any intervening ligand. This type of polymeric paddlewheel structures are found very rarely. Each copper is lying in a CuO₅ square pyramid coordinated by four oxygen atoms in the square base while the axial oxygen belongs to the neighboring paddlewheel. Purity and uniform crystalline nature of the complex was assessed from matching theoretical and experimental powder XRD spectra. ESR spectrum consisted of a broad signal with g value = 2.2427, whereas electrochemical studies revealed diffusion controlled electron transfer processes with diffusion co‐efficient = 1.628 × 10^–7 cm² · s^–1. The results of spectroscopic techniques support each other. The complex afforded mixed binding mode with DNA yielding DNA‐binding constant values of 1.384 × 10⁴ m ^–1 and 8.845 × 10⁴ m ^–1 using absorption spectroscopy and cyclic voltammetry, respectively. The complex also exhibited significant activity against anti‐fungal strain Helminthosporium solani by inhibiting its 75 % ± 2.5 growth. The preliminary studies heralded excellent biological potential of the synthesized complex.     

Electrocatalytic Reduction and Determination of Iodate and Periodate at Silicomolybdate‐Incorporated‐Glutaraldehyde‐ Cross‐Linked Poly‐L‐lysine Film Electrodes

The present work describes reduction of iodate (IO₃^?), and periodate (IO₄^?) at silicomolybdate‐doped‐glutaraldehyde‐cross‐linked poly‐L ‐lysine (PLL‐GA‐SiMo) film coated glassy carbon electrode in 0.1 M H₂SO₄. In our previous study, we were able to prepare the PLL‐GA‐SiMo film modified electrode by means of electrostatically trapping SiMo₁₂O₄₀^4? mediator in the cationic film of PLL‐GA, and the voltammetric investigation in pure supporting indicated that the charge transport through the film was fast. Here, the electrocatalytic activity of PLL‐GA‐SiMo film electrode towards iodate and periodate was tested and subsequently used for analytical determination of these analytes by amperometry. The two electron reduced species of SiMo₁₂O₄₀^4? anion was responsible for the electrocatalytic reduction of IO₃^? at PLL‐GA‐SiMo film electrode while two and six electron reduced species were showed electrocatalytic activity towards IO₄^? reduction. Under optimized experimental conditions of amperometry, the linear concentration range and sensitivity are 2.5×10^?6 to 1.1×10^?2 M and 18.47 μA mM^?1 for iodate, and 5×10^?6 to 1.43×10^?4 M and 1014.7 μA mM^?1 for periodate, respectively.