Two-dimensional separation of [7]helicene enantiomers on Cu(111).

The adsorption of heptahelicene, a helically shaped polyaromatic hydrocarbon (C(30)H(18)), on a Cu(111) surface was studied by means of thermal desorption mass spectrometry (TDMS) and low energy electron diffraction (LEED) at temperatures between 130-1,000 K under ultrahigh vacuum (UHV) conditions. The molecule in the monolayer remains intact up to 400 K. Above that temperature it decomposes in several steps into carbon and hydrogen, desorbing subsequently as H(2). In the saturated monolayer of the racemate the enantiomers are separated into two different domains on the surface which are mirror images of each other. After adsorption of one enantiomer only, no mirror domains were observed.     

Prion protein does not redox-silence Cu2+, but is a sacrificial quencher of hydroxyl radicals

Oxidative stress is believed to play a central role in the pathogenesis of prion diseases, a group of fatal neurodegenerative disorders associated with a conformational change in the prion protein (PrP(C)). The precise physiological function of PrP(C) remains uncertain; however, Cu(2+) binds to PrP(C) in vivo, suggesting a role for PrP(C) in copper homeostasis. Here we examine the oxidative processes associated with PrP(C) and Cu(2+). (1)H NMR was used to monitor chemical modifications of PrP fragments. Incubation of PrP fragments with ascorbate and CuCl(2) showed specific metal-catalyzed oxidation of histidine residues, His(96/111), and the methionine residues, Met(109/112). The octarepeat region protects His(96/111) and Met(109/112) from oxidation, suggesting that PrP(90-231) might be more prone to chemical modification. We show that Cu(2+/+) redox cycling is not 'silenced' by Cu(2+) binding to PrP, as indicated by H(2)O(2) production for full-length PrP. Surprisingly, although detection of Cu(+) indicates that the octarepeat region of PrP is capable of reducing Cu(2+) even in the absence of ascorbate, H(2)O(2) is not generated unless ascorbate is present. Full-length PrP and fragments cause a dramatic reduction in detectable hydroxyl radicals in an ascorbate/Cu(2+)/O(2) system; however, levels of H(2)O(2) production are unaffected. This suggests that PrP does not affect levels of hydroxyl radical production via Fentons cycling, but the radicals cause highly localized chemical modification of PrP(C).     

纳米δ-Bi2O3负载多孔沸石球填料对水体中Cr（Ⅵ）的吸附特征及其影响因素

在水热条件下合成纳米δ-Bi2O3负载多孔沸石球填料(Bi-PZSF),研究其对水体中Cr(Ⅵ)的吸附性能(包括等温吸附、吸附动力学和吸附稳定性)以及溶解氧、pH等因素对吸附过程的影响及其吸附机理。结果表明:朗格缪尔模型和准二级动力学模型对实验结果具有良好的拟合度,在中性条件下,水体中的溶解氧含量对吸附速率影响较小,Bi-PZSF的最大吸附量为955.69 mg·kg^-1,比天然沸石的吸附量提升了近120倍;Bi-PZSF在NO3^-和SO4^2-的溶液中呈现出较强的选择吸收Cr(Ⅵ)能力,Cr(Ⅵ)去除率均在97%以上;同时,Bi-PZSF在吸附Cr(Ⅵ)后表现出高稳定性。Cr(Ⅵ)的去除主要是通过与附着在Bi-PZSF上的纳米δ-Bi2O3的表面羟基交换完成的。     

Immobilization of oriented protein molecules on poly(ethylene glycol)-coated Si(111)

A high-density poly(ethylene glycol) (PEG)-coated Si(111) surface is used for the immobilization of polyhistidine-tagged protein molecules. This process features a number of properties that are highly desirable for protein microarray technology: (i) minimal nonspecific protein adsorption; (ii) highly uniform surface functionality; (iii) controlled protein orientation; and (iv) highly specific immobilization reaction without the need of protein purification. The high-density PEG-coated silicon surface is obtained from the reaction of a multi-arm PEG (mPEG) molecule with a chlorine terminated Si(111) surface to give a mPEG film with thickness of 5.2 nm. Four out of the eight arms on each immobilized mPEG molecule are accessible for linking to the chelating iminodiacetic acid (IDA) groups for the binding of Cu(2+) ions. The resulting Cu(2+)-IDA-mPEG-Si(111) surface is shown to specifically bind 6x histidine-tagged protein molecules, including green fluorescent protein (GFP) and sulfotransferase (ST), but otherwise retains its inertness towards nonspecific protein adsorption. We demonstrate a particular advantage of this strategy: the possibility of protein immobilization without the need of prepurification. Surface concentrations of relevant chemical species are quantitatively characterized at each reaction step by X-ray photoelectron spectroscopy (XPS). This kind of quantitative analysis is essential in tuning surface concentration and chemical environment for optimal sensitivity in probe-target interaction.     

DFT modelling of hydrogen on Cu(110)- and (111)-type clusters

Density Functional Theory (DFT) calculations using gaussian 98 have been performed on hydrogen adsorbed on clusters representing the (110) and (111) surfaces of Cu. Clusters were constructed to model different adsorption sites, and at least two different size clusters were used for each site. On the (111) surface, hydrogen prefers to adsorb in a hollow site, though with the hcp variant being favoured by the adsorption energy, and the fcc alternative by the vibrational frequencies. On the (110) surface, the "fcc" site on a (1 2 2) reconstructed surface is preferred.     

Adsorption and decomposition mechanism of hexogen (RDX) on Al(111) surface by periodic DFT calculations

The adsorption of hexogen (RDX) molecule on the Al(111) surface was investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employ a supercell (4×4×3) slab model and three-dimensional periodic boundary conditions. The strong attractive forces between RDX molecule and aluminum atoms induce the N?O and N?N bond breaking of the RDX. Subsequently, the dissociated oxygen atoms, NO₂ group and radical fragment of RDX oxidize the Al surface. The largest adsorption energy is ?835.7 kJ mol^–1. We also investigated the adsorption and decomposition mechanism of RDX molecule on the Al(111) surface. The activation energy for the dissociation steps of V4 configuration is as large as 353.1 kJ mol^–1, while activation energies of other configurations are much smaller, in the range of 70.5–202.9 kJ mol^–1. The N?O is even easier than the N?NO₂ bond to decompose on the Al(111) surface.     

Interactions between metal ions and carbohydrates: the coordination behavior of neutral erythritol to transition metal ions

The single crystals of coordinated complexes of neutral erythritol (C4H10O4) with various transition metal ions were synthesized and studied using FT-IR and single crystal X-ray diffraction analysis. Two CuCl2-erythritol complexes (denoted as CuE(I) and CuE(II)) were obtained. In CuE(I), Cu2+ coordinates with two chloride ions and four OH groups from two erythritol molecules. Two copper centers are linked by one erythritol molecule to form a zigzag chain. For CuE(II), each Cu2+ coordinates with two OH groups from an erythritol molecule and two chloride ions. The crystal of CuE(II) contains complexed and free erythritol, the dimers of [Cu2Cl4(C4H10O4)] further form a [Cu2Cl4(C4H10O4)]infinity chain via secondary Cu...Cl bonds, both the dimer unit of [Cu2Cl4.(C4H10O4)] and non-coordinated C4H10O4 unit exist side by side in the crystal. MnCl2-erythritol complex whose structure is similar to CuE(I) is also acquired. The OH groups of erythritol act as ligand to coordinate to metal ions on one hand, one the other hand, OH groups form hydrogen bonds network that link chain and layer together to build three-dimensional structures.     

Mechanism of oxidative DNA damage induced by carcinogenic 4-aminobiphenyl

DNA adduct formation is thought to be a major cause of DNA damage by carcinogenic aromatic amines. We investigated the ability of an aromatic amine, 4-aminobiphenyl (4-ABP) and its N-hydroxy metabolite (4-ABP(NHOH)) to cause oxidative DNA damage, using (32)P-labeled human DNA fragments from the p53 tumor suppressor gene and the c-Ha-ras-1 protooncogene. 4-ABP(NHOH) was found to cause Cu(II)-mediated DNA damage, especially at thymine residues. Addition of the endogenous reductant NADH led to dramatic enhancement of this process. Catalase and bathocuproine, a Cu(I)-specific chelator, reduced the amount of DNA damage, suggesting the involvement of H(2)O(2) and Cu(I). 4-ABP(NHOH) dose-dependently induced 8-hydroxy-2'-deoxyguanosine (8-OHdG) formation in the presence of Cu(ll) and NADH. 4-ABP(NHOH) conversion to nitrosobiphenyl, as measured by UV-visible spectroscopy, occurred rapidly in the presence of Cu(II), suggesting Cu(II)-mediated autoxidation. Increased amounts of 8-OHdG were found in HL-60 cells compared to the H(2)O(2)-resistant clone HP100 following 4-ABP(NHOH) treatment, further supporting the involvement of H(2)O(2). The present study demonstrates that an N-hydroxy derivative of 4-ABP induces oxidative DNA damage through H(2)O(2) in both a cell-free system and in cultured human cells. We conclude that, in addition to DNA adduct formation, oxidative DNA damage may play an important role in the carcinogenic process of 4-ABP.     

Inhibition of rat synaptic membrane Na⁺/K⁺-ATPase and ecto-nucleoside triphosphate diphosphohydrolases by 12-tungstosilicic and 12-tungstophosphoric acid

The in vitro influence of Keggin structure polyoxotungstates, 12-tungstosilicic acid, H(4)SiW(12)O(40) (WSiA) and 12-tungstophosphoric acid, H(3)PW(12)O(40) (WPA), and monomer Na(2)WO(4) × 2H(2)O on rat synaptic plasma membrane (SPM) Na(+)/K(+)-ATPase and E-NTPDase activity was studied, whereas the commercial porcine cerebral cortex Na(+)/K(+)-ATPase served as a reference. Dose-dependent Na(+)/K(+)-ATPase inhibition was obtained for all investigated compounds. Calculated IC(50) (10 min) values, in mol/l, for SPM/commercial Na(+)/K(+)-ATPase, were: 3.4 × 10(-6)/4.3 × 10(-6), 2.9 × 10(-6)/3.1 × 10(-6) and 1.3 × 10(-3)/1.5 × 10(-3) for WSiA, WPA and Na(2)WO(4) × 2H(2)O, respectively. In the case of E-NTPDase, increasing concentrations of WSiA and WPA induced its activity reduction, while Na(2)WO(4) × 2H(2)O did not noticeably affect the enzyme activity at all investigated concentrations (up to 1 × 10(-3)mol/l). IC(50) (10 min) values, obtained from the inhibition curves, were (in mol/l): 4.1 × 10(-6) for WSiA and 1.6 × 10(-6) for WPA. Monolacunary Keggin anion was found as the main active molecular species present under physiological conditions (in the enzyme assays, pH 7.4), for the both polyoxotungstates solutions (1 mmol/l), using Fourier transform infrared (FT-IR) and micro-Raman spectroscopy. Additionally, commercial porcine cerebral cortex Na(+)/K(+)-ATPase was exposed to the mixture of Na(2)WO(4) × 2H(2)O and WSiA at different concentrations. Additive inhibition effect was achieved for lower concentrations of Na(2)WO(4) × 2H(2)O/WSiA (≤ 1 × 10(-3)/4 × 10(-6) mol/l), while antagonistic effect was obtained for all higher concentrations of the inhibitors.     

Probing copper2+ binding to the prion protein using diamagnetic nickel2+ and 1H NMR: the unstructured N terminus facilitates the coordination of six copper2+ ions at physiological concentrations

The prion protein (PrP) is a Cu2+ binding cell surface glyco-protein. Misfolding of PrP into a beta-sheet rich conformation is associated with transmissible spongiform encephalopathies. Here we use Ni2+ as a diamagnetic probe to further understand Cu2+ binding to PrP. Like Cu2+, Ni2+ preferentially binds to an unstructured region between residues 90 and 126 of PrP, which is a key region for amyloidogenicity and prion propagation. Using both 1H NMR and visible-circular dichroism (CD) spectroscopy, we show that two Ni2+ ions bind to His96 and His111 independently of each other. 1H NMR indicates that both Ni2+ binding sites form square-planar diamagnetic complexes. We have previously shown that Cu2+ forms a paramagnetic square-planar complex in this region, suggesting that Ni2+ could be used as a probe for Cu2+ binding. In addition, competition studies show that two Cu2+ ions can displace Ni2+ from these sites. Upon Ni2+ addition 1H NMR changes in chemical shifts indicate the imidazole ring and amide nitrogen atoms to the N terminus of both His96 and His111 act as coordinating ligands. Use of peptide fragments confirm that PrP(92-96) and PrP(107-111) represent the minimal binding motif for the two Ni2+ binding sites. Analysis of Cu2+ loaded visible-CD spectra show that as with Ni2+, PrP(90-115) binds two Cu2+ ions at His96 and His111 independently of each other. Visible CD studies with PrP(23-231Delta51-90), a construct of PrP(23-231) with the octarepeat region deleted to improve solubility, confirm binding of Ni2+ to His96 and His111 in octarepeat deleted PrP(23-231). The structure of the Cu/Ni complexes is discussed in terms of the implications for prion protein function and disease.     

Synthesis, structure, and nuclease properties of several binary and ternary complexes of copper(II) with norfloxacin and 1,10 phenantroline

Three new binary Cu(II) complexes of norfloxacin have been synthesized and characterized. We also report the synthesis, characterization and X-ray crystallographic structures of a new binary compound, [Cu(HNor)(2)]Cl(2).2H(2)O (2) and two new ternary complexes norfloxacin-copper(II)-phen, [Cu(Nor)(phen)(H(2)O)](NO(3)).3H(2)O (4), and [Cu(HNor)(phen)(NO(3))](NO(3)).3H(2)O (5). The structure of 2 consists of two crystallographically independent cationic monomeric units of [Cu(HNor)(2)](2+), chloride anions, and uncoordinated water molecules. The Cu(II) ion is placed at a center of symmetry and is coordinated to two norfloxacin ligands which are related through the inversion center. The structures of 4 and 5 consist of cationic units ([Cu(Nor)(phen)(H(2)O)](+) for 4 and [Cu(HNor)(phen)(NO(3))](+) for 5), nitrate counteranions, and lattice water molecules that provide crystalline stability through a network of hydrogen-bond interactions. The complexes exhibit a five coordinated motif in a square pyramidal environment around the metal center. The ability of compounds 4 and 5 to cleave DNA has also been studied. Mechanistic studies with different inhibiting reagents reveal that hydroxyl radicals, singlet oxygen, and superoxide radicals are all involved in the DNA scission process mediated by these compounds.     

Low-temperature (180 K) crystal structures of tetrakis-mu-(niflumato)di(aqua)dicopper(II) N,N-dimethylformamide and N,N-dimethylacetamide solvates, their EPR properties, and anticonvulsant activities of these and other ternary binuclear copper(II)niflumate complexes

Two pseudopolymorphs, solvates, of [Cu(2)(II)(niflumate)(4)(H(2)O)(2)] of unknown structure were obtained following solution of [Cu(2)(II)(niflumate)(4)(H(2)O)(2)] in N,N-dimethylacetamide (DMA) or N,N-dimethylformamide (DMF). Low-temperature crystal structures obtained for these solvates revealed that they were ternary aqua DMA and DMF solvates: [Cu(2)(II)(niflumate)(4)(H(2)O)(2)].4DMA and [Cu(2)(II)(niflumate)(4)(H(2)O)(2)].4DMF. Intermolecular hydrogen bonding interactions account for the formation of these stable DMA and DMF solvates. These pseudopolymorphs contain a centrosymmetric binuclear center with Cu-Cu bond distances ranging from 2.6439(7) to 2.6452(9) A; the coordination sphere of Cu(II) is characterized by one long Cu-O (water) bond length of 2.128(3)-2.135(3) A and four short Cu-O (carboxylate) bonds of 1.949(3)-1.977(3) A. Crystal parameters for the DMA pseudopolymorph: a=10.372(1), b=19.625(2), c=17.967(2) A, beta=97.40(1) degrees , V=3626.8(6) A(3); monoclinic system; space group: P2(1)/a and for the DMF pseudopolymorph: a=10.125(2), b=18.647(3), c=19.616(4) A, alpha=74.38(2)(o), beta=88.18(2)(o), gamma=79.28(2)(o), V=3504(1) A(3); triclinic system; space group: P1. EPR spectra of these solids are identical and show strong antiferromagnetic coupling between the copper atoms, similar to the spectrum obtained for [Cu(2)(II)(niflumate)(4)(DMSO)(2)]. The [Cu(2)(II)(niflumate)(4)(H(2)O)(2)], [Cu(2)(II)(niflumate)(4)(H(2)O)(2)].4DMA, [Cu(2)(II)(niflumate)(4)(H(2)O)(2)].4DMF, [Cu(2)(II)(niflumate)(4)(DMF)(2)], and[Cu(2)(II)(niflumate)(4)(DMSO)(2)] evidenced protection against maximal electroshock-induced seizures and Psychomotor seizures at various times after treatment, consistent with the well known antiinflammatory activities of Cu chelates, but failed to protect against Metrazol-induced seizures while evidencing some Rotorod Toxicity consistent with a mechanism of action involving sedative activity.     

Crystal structure, solid state and solution characterisation of copper(II) coordination compounds of ethyl 5-methyl-4-imidazolecarboxylate (emizco)

The synthesis and characterisation of the following compounds derived from the biological relevant compound ethyl 5-methyl-4-imidazolecarboxylate (emizco) (1): [Cu(emizco)Cl2] (2), [Cu(emizco)2Cl2] (3), [Cu(emizco)2Br2] (4), [Cu(emizco)2(H2O)2](NO3)2 (5) and [Cu(emizco)4](NO3)2 (6), is presented. These compounds were characterised by IR and UV spectroscopic techniques, in addition the crystal structures of compounds 1-5 were determined. For complexes 2-5, emizco is coordinated as a bidentate ligand, through the oxygen atom of the carboxylate moiety and the nitrogen atom of the imidazolic ring. Different geometries are stabilised: compound 2 includes a pentacoordinated square pyramidal metal centre, while 3-5 are derived from octahedral geometry. Halide compounds 3 and 4 show a cis-octahedral arrangement, which is not very common on [CuN2O2X2] systems, while 5 stabilises the trans-octahedral isomer. Compound 6 displays a square planar geometry. Finally, hydrolysis of emizco to its corresponding carboxylic acid (mizco), allowed the preparation of another square planar complex 7, identified as [Cu(mizco)2] 0.5H2O. Solution studies of these compounds indicate that emizco is not substituted from the coordination sphere, remaining as a bidentate ligand. Halides are substituted by water molecules, changing from cis octahedral to the trans-[Cu(emizco)2(H2O)2]2+ isomer.     

Polyoxometalates as peroxidase mimetics and their applications in H2O2 and glucose detection

Polyoxometalates (H(3)PW(12)O(40), H(4)SiW(12)O(40) and H(3)PMo(12)O(40)) have been proven to possess intrinsic peroxidase-like activity for the first time, which can catalyze oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) by H(2)O(2) to form a blue color in aqueous solution. Among them, H(3)PW(12)O(40) (PW(12)) exhibits higher catalytic activity to TMB than natural enzyme HRP and other two POMs. In addition, H(3)PW(12)O(40)/graphene exhibited higher activity than H(3)PW(12)O(40) in this catalytic oxidation reaction due to the effect of graphene in promoting the electron transfer between the substrate and catalyst. POMs/H(2)O(2)/TMB system provides a simple, accurate approach to colorimetric detection for H(2)O(2) or glucose. The colorimetric method based on POMs showed good response toward H(2)O(2) and glucose detection with a linear range from 1.34×10(-7) to 6.7×10(-5) mol/L and 1×10(-7) to 1×10(-4) mol/L, respectively. The results showed that it is a simple, cheap, more convenient, highly selective, sensitive, and easy handling colorimetric assay.     

Hydrogen peroxide-induced carbonylation of key metabolic enzymes in Saccharomyces cerevisiae: the involvement of the oxidative stress response regulators Yap1 and Skn7

H(2)O(2) induces a specific protein oxidation in yeast cells, and the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (Tdh) is a major target. Using a 2D-gel system to study protein carbonylation, it is shown in this work that both Tdh2p and Tdh3p isozymes were oxidized during exposure to H(2)O(2). In addition, we identified two other proteins carbonylated and inactivated: Cu,Zn-superoxide dismutase and phosphoglycerate mutase. The oxidative inactivation of Cu,Zn-superoxide dismutase decreases the antioxidant capacity of yeast cells and probably contributes to H(2)O(2)-induced cell death. Cyclophilin 1 was also carbonylated, but CPH1 gene disruption did not affect peroxide stress sensitivity. The correlation between H(2)O(2) sensitivity and the accumulation of oxidized proteins was evaluated by assaying protein carbonyls in mutants deficient in the stress response regulators Yap1p and Skn7p. The results show that the high sensitivity of yap1delta and skn7delta mutants to H(2)O(2) was correlated with an increased induction of protein carbonylation. In wild-type cells, the acquisition of stress resistance by pre-exposure to a sublethal H(2)O(2) stress was associated with a lower accumulation of oxidized proteins. However, pre-exposure of yap1delta and skn7delta cells to 0.4 mM H(2)O(2) decreased protein carbonylation induced by 1.5 mM H(2)O(2), indicating that the adaptive mechanism involved in the protection of proteins from carbonylation is Yap1p- and Skn7p-independent.     

Distinct mechanisms of oxidative DNA damage by two metabolites of carcinogenic o-toluidine

Mechanisms of DNA damage by metabolites of carcinogenic o-toluidine in the presence of metals were investigated by the DNA sequencing technique using (32)P-labeled human DNA fragments. 4-Amino-3-methylphenol, a major metabolite, caused DNA damage in the presence of Cu(II). Predominant cleavage sites were thymine and cytosine residues. o-Nitrosotoluene, a minor metabolite, did not induce DNA damage even in the presence of Cu(II), but addition of NADH induced DNA damage very efficiently. The DNA cleavage pattern was similar to that in the case of 4-amino-3-methylphenol. Bathocuproine and catalase inhibited DNA damage by these o-toluidine metabolites, indicating the participation of Cu(I) and H(2)O(2) in the DNA damage. Typical free hydroxyl radical scavengers showed no inhibitory effects on the DNA damage. o-Toluidine metabolites increased the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine in calf thymus DNA in the presence of Cu(II). UV-visible and ESR spectroscopic studies have demonstrated that 4-amino-3-methylphenol is autoxidized to form the aminomethylphenoxyl radical and o-nitrosotoluene is reduced by NADH to the o-toluolhydronitroxide radical in the presence and absence of Cu(II). Consequently, it is considered that these radicals react with O(2) to form O(-)(2) and subsequently H(2)O(2), and that the reactive species generated by the reaction of H(2)O(2) with Cu(I) participate in the DNA damage. Metal-mediated DNA damage by o-toluidine metabolites through H(2)O(2) seems to be relevant for the expression of the carcinogenicity of o-toluidine.     

Syntheses, crystal structures, and oxidative DNA cleavage of some Cu(II) complexes of 5-amino-3-pyridin-2-yl-1,2,4-triazole

Three new monomeric Cu(II) complexes of 5-amino-3-pyridin-2-yl-1,2,4-triazole (Hapt), [Cu(Hapt)(H(2)O)(2)(SO(4))] (1), [Cu(Hapt)(2)(H(2)O)(NO(3))](NO(3)) (2), and [Cu(Hapt)(2)(NCS-N)](NCS).H(2)O (3), have been prepared and characterized by single crystal X-ray diffraction. One distorted [CuN(2)O(2)+O(')] square-pyramidal (1), one distorted [CuN(3)O+N(')+O(')] octahedral (2), and one distorted [CuN(4)+N(')] intermediate between square-pyramidal and trigonal-bipyramidal (3) coordination configuration were found and are suggested to be due to the chelating nature of the ligand, which interacts with Cu(II) through the N4(triazole) and N(pyridine) atoms. Spectral properties of these chelates are in accordance with the X-ray structural data. With ascorbate and H(2)O(2) activation, compound 2 exhibits higher nuclease activity than compound 1. The influence on the DNA cleavage process of different scavengers of reactive oxygen species: dimethyl sulfoxide (DMSO), tert-butyl alcohol, sodium azide, 2,2,6,6-tetramethyl-4-piperidone and superoxide dismutase enzyme (SOD), and of the minor groove binder distamycin, is also studied.     

Molecular recognition patterns of 2-aminopurine versus adenine: a view through ternary copper(II) complexes

In contrast to the comprehensive structural information about metal complexes with adenine, the corresponding to its isomer 2-aminopurine (H2AP) is extremely poor. With the aim to rationalize the metal binding pattern of H2AP, we report the molecular and/or crystal structure of four novel compounds with various iminodiacetate-like (IDA-like) copper(II) chelates: [Cu(IDA)(H2AP)(H2O)]·H2O (1), [Cu(MIDA)(H2AP)(H2O)]·3H2O (2), {[Cu(NBzIDA)(H2AP)]·1.5H2O}n (3) and [Cu(MEBIDA)(H2AP)(H2O)]·3.5 H2O (4), where IDA, MIDA, NBzIDA and MEBIDA are R = H, CH3, benzyl- and p-tolyl- in R-N-(CH2-COO-)2 ligands, respectively. Synthesis strategies include direct reactions of copper(II) chelates with H2AP (alone, for 1 and 3) and/or with the base pairs H2AP:thymine (1-4) or H2AP:cytosine (3). Moreover, these compounds have been also investigated by spectral and thermal methods. Regardless of the N-derivative of the IDA chelator, molecular recognition between H2AP and the referred Cu(II)-chelates only displays the formation of the Cu-N7(purine-like) bond what is clearly in contrast to what was previously reported for adenine. The metal binding pattern of 2-aminopurine is discussed on the basis of the electronic effects and steric hindrance of the 2-amino exocyclic group.     

Histone peptide AKRHRK enhances H(2)O(2)-induced DNA damage and alters its site specificity

Histone proteins are involved in compaction of DNA and the protection of cells from oxygen toxicity. However, several studies have demonstrated that the metal-binding histone reacts with H(2)O(2), leading to oxidative damage to a nucleobase. We investigated whether histone can accelerate oxidative DNA damage, using a minimal model for the N-terminal tail of histone H4, CH(3)CO-AKRHRK-CONH(2), which has a metal-binding site. This histone peptide enhanced DNA damage induced by H(2)O(2) and Cu(II), especially at cytosine residues, and induced additional DNA cleavage at the 5'-guanine of GGG sequences. The peptide also enhanced the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine and ESR spin-trapping signal from H(2)O(2) and Cu(II). Cyclic redox reactions involving histone-bound Cu(II) and H(2)O(2), may give rise to multiple production of radicals leading to multiple hits in DNA. It is noteworthy that the histone H4 peptide with specific sequence AKRHRK can cause DNA damage rather than protection under metal-overloaded condition.     

Ambient temperature detection of PCR amplicons with a novel sequence-specific nucleic acid lateral flow biosensor

The spherical porous Pd nanoparticle assemblies (NPAs) have been successfully synthesized by starch-assisted chemical reduction of Pd(II) species at room temperature. Such Pd NPAs are not simply used to enlarge the surface area and to promote the electron transfer. They also catalyze the reduction of H(2)O(2) which are regarded as horseradish peroxidase (HRP) substitutes in electron transfer process. By using them as electrocatalysts, as low as 6.8×10(-7) M H(2)O(2) can be detected with a linear range from 1.0×10(-6) to 8.2×10(-4) M. Moreover, through co-immobilization of such Pd NPAs and glucose oxidase (GOx), a sensitive and selective glucose biosensor is developed. The detection principle lies on measuring the increase of cathodic current by co-reduction of dissolved oxygen and the in situ generated H(2)O(2) during the enzymatic reaction. Under optimal conditions, the detection limit is down to 6.1×10(-6) M with a very wide linear range from 4.0×10(-5) to 2.2×10(-2) M. The proposed biosensor shows a fast response, good stability, high selectivity and reproducibility of serum glucose level. It provides a promising strategy to construct fast, sensitive, stable and anti-interferential amperometric biosensors for early diagnosis and prevention of diabetes.