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The focus of this study is in the description of synthetic heme/copper/O2 chemistry employing a heme-containing binucleating ligand which provides a tridentate chelate for copper ion binding. The a...

A novel thymine-containing chitosan derivative has been designed, synthesized, and used for the first time in this work for removal of some commercial pesticides from synthetic wastewater by coagulation/flocculation. The chitosan-thymine conjugate was characterized by 1H NMR and FT-IR spectroscopy, and its flocculation performance was evaluated by UV–Vis spectroscopy in comparison to non-modified chitosan. The commercial pesticides used in this investigation were Fastac 10 EC and Karate Zeon (with alpha-Cypermethrin and lambda- Cyhalothrin, respectively, as active pyrethroid ingredients), Novadim Progress (Dimethoate as active organophosphoric ingredient), and Bordeaux mixture. The experimental results demonstrate good removal efficiency for Karate Zeon (between 80 and 85%), a maximum of around 90% for Fastac 10EC and Novadim Progress, and more than 95% for the Bordeaux mixture, irrespective of the polycation structure. According to the zeta potential values recorded in the optimum dose interval, the flocculation of pyrethroid pesticides particles took place mainly by means of the charge neutralization mechanism (close to zero), whereas the flocculation of Novadim Progress and Bordeaux mixture particles has been achieved by the synergistic effect of charge neutralization and hydrogen bonding (Novadim Progress) or copper ion binding by the amine and thymine groups (Bordeaux Mixture) (negative values).

Animal pigmentation primarily depends on the presence and mixing ratio of chromatophores, functioning in animal survival and communication. For the benthic and carnivorous Siniperca chuatsi, pigmentation pattern is key to concealment and predation. In this study, the formation, distribution, and main pattern of chromatophores were observed in the embryos, larvae, skins, and visceral tissues from S. chuatsi. Melanophores were firstly visualized in the yolk sac at segmentation stage, and then they were migrated to the whole body and further clustered into the black stripes, bands, and patches. In adult S. chuatsi, the head, black band, and body side skins mainly contained melanophores, showing as deep or light black. The abdomen skin mainly contained iridophores, showing as silvery. In the eye, the pigment layers were located in the epithelial layers of iris and retina and shown as black. Then, the pigmentation-related gene, tyrosinase gene from S. chuatsi (Sc-tyr) was analyzed by bioinformatics and quantitative methods. The Sc-tyr gene encoded a protein with 540 amino acids (Sc-TYR). The Sc-TYR contained two copper ion binding sites, which were coordinated by six conserved histidines (H182, H205, H214, H366, H370, H393) and necessary for catalytic activity. The Sc-TYR was well conserved compared with TYR of various species with higher degree of sequence similarity with other fishes (77.6-98.3%). The qRT-PCR test showed that the Sc-tyr mRNA reached the peak value at segmentation stage in the embryo development, the black skins displayed a higher expression level than that in silvery skin, and the eye had the highest expression level compared with other tissues. Further research on enzyme activity showed that the expression patterns of tyrosinase activity were similar to that of the Sc-tyr mRNA. Comparing with the results of molecular and phenotype, it was found that the temporal and spatial distributions of tyrosinase corresponded well with changes in pigmentation patterns and the intensity of skin melanization. This study initially explored the pigmentation formation and tyrosinase expression, which served as a foundation for further insight into the genetics mechanism of body color formation in S. chuatsi.

Zinc and copper are essential metal ions for numerous biological processes. Their levels are tightly maintained in all body organs. Impairment of the Zn2+ to Cu2+ ratio in serum was found to correlate with many disease states, including immunological and inflammatory disorders. Oxytocin (OT) is a neuropeptide, and its activity is modulated by zinc and copper ion binding. Harnessing the intrinsic properties of OT is one of the attractive ways to develop valuable metal ion sensors. Here, we report for the first time an OT-based metal ion sensor prepared by immobilizing the neuropeptide onto a glassy carbon electrode. The developed impedimetric biosensor was ultrasensitive to Zn2+ and Cu2+ ions at physiological pH and not to other biologically relevant ions. Interestingly, the electrochemical impedance signal of two hemicircle systems was recorded after the attachment of OT to the surface. These two semicircles suggest two capacitive regions that result from two different domains in the OT monolayer. Moreover, the change in the charge-transfer resistance of either Zn2+ or Cu2+ was not similar in response to binding. This suggests that the metal-dependent conformational changes of OT can be translated to distinct impedimetric data. Selective masking of Zn2+ and Cu2+ was used to allow for the simultaneous determination of zinc to copper ions ratio by the OT sensor. The OT sensor was able to distinguish between healthy control and multiple sclerosis patients diluted sera samples by determining the Zn/Cu ratio similar to the state-of-the-art techniques. The OT sensor presented herein is likely to have numerous applications in biomedical research and pave the way to other types of neuropeptide-derived sensors.

New push-pull schiff base ligands based on benzothiazole (BZ) unit were developed for the selective detection of Cu2+ through fluorescence ‘turn-on’ mechanism. These derivatives with electron withdrawing trifluoromethyl (-CF3) and cyano (-CN) substituents (BZ2 and BZ3) demonstrated a prominent fluorescence enhancement upon copper ion binding which could be the results from the synergistic effect between the chelation-enhanced fluorescence (CHEF) and the intramolecular charge transfer (ICT) processes. In addition, these compounds displayed 1:1 binding with Cu2+ with low limits of detection of 0.77 μM and 0.64 μM for BZ2 and BZ3, respectively, in acetonitrile-water (3:1 v/v) media. The electronic and photophysical properties of these BZ ligands and the copper ion complexes were modelled by the density functional theory (DFT) and the time-dependent density functional theory (TD-DFT) calculations, respectively. Analysis of X-ray absorption spectra probed at Cu K-edge of Cu2+-BZ mixtures revealed the complex formation of BZ ligands with the targeted Cu2+ and confirmed the non-centrosymetric structures of the complexes as predicted by the DFT calculation. The electron density distributions of the HOMO-LUMOs in the computational results as well as large stokes shifts of the ligand-metal complexes in the experimental data confirmed the strong ICT effect after Cu2+ binding which is a key process promoting fluorescence ‘turn-on’ mechanism.

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal disease characterized by cortical and spinal motor neuron degeneration, some inherited cases of which are caused by mutations in the gene coding for copper-zinc superoxide dismutase-1 (SOD1). The SOD1G93A mutant model mouse, which expresses large amounts of mutant SOD1, develops adult-onset neurodegeneration of spinal motor neurons and progressive motor deficits leading to paralysis. We used the Tandem Mass Tag technique to investigate the proteome profile of hippocampus, cerebral cortex, and medulla oblongata of the SOD1G93A mutant model mice as compared with that of wild-type (WT) mice. Fifteen proteins were significantly increased or decreased (i.e., changed) in all three tissues. Gene ontology analysis revealed that the changed proteins were mainly enriched in negative regulation of reactive oxygen species, myosin complex and copper ion binding. In the Striated Muscle Contraction Pathway, most of the identified proteins were decreased in the SOD1G93A mice compared with the WT mice. Myosin-1 (MYH1), fructose-2,6-bisphosphatase TIGAR (TIGAR), and sarcoplasmic/endoplasmic reticulum calcium ATPase 1 (ATP2A1) were significantly reduced in mutant vs WT mice, as confirmed by Western blot analysis. Since myosins and tropomyosins are specific for synapse function and drive actin dynamics in the maturation of dendritic spines, changes in these proteins may contribute to perturbations of brain neuronal circuitry in addition to spinal motor neuron disease.

β-Amyloid aggregates in the brain play critical roles in Alzheimer's disease, a chronic neurodegenerative condition. Amyloid-associated metal ions, particularly zinc and copper ions, have been implicated in disease pathogenesis. Despite the importance of such ions, the binding sites on the β-amyloid peptide remain poorly understood. In this study, we use scanning tunneling microscopy, circular dichroism, and surface-enhanced Raman spectroscopy to probe the interactions between Cu2+ ions and a key β-amyloid peptide fragment, consisting of the first 16 amino acids, and define the copper-peptide binding site. We observe that in the presence of Cu2+, this peptide fragment forms β-sheets, not seen without the metal ion. By imaging with scanning tunneling microscopy, we are able to identify the binding site, which involves two histidine residues, His13 and His14. We conclude that the binding of copper to these residues creates an interstrand histidine brace, which enables the formation of β-sheets.

Type-2 diabetes (T2D) is considered to be a potential threat on a global level. Recently, T2D has been listed as a misfolding disease, such as Alzheimer's and Parkinson's diseases. Human islet amyloid polypeptide (hIAPP) is a molecule cosecreted in pancreatic β cells and represents the main constituent of an aggregated amyloid found in individuals affected by T2D. The trace-element serum level is significantly influenced during the development of diabetes. In particular, the dys-homeostasis of Cu(2+) ions may adversely affect the course of the disease. Conflicting results have been reported on the protective role played by complex species formed by Cu(2+) ions with hIAPP or its peptide fragments in vitro. The histidine (His) residue at position 18 represents the main binding site for the metal ion, but contrasting results have been reported on other residues involved in metal-ion coordination, in particular those toward the N or C terminus. Sequences that encompass regions 17-29 and 14-22 were used to discriminate between the two models of the hIAPP coordination mode. Due to poor solubility in water, poly(ethylene glycol) (PEG) derivatives were synthesized. A peptide fragment that encompasses the 17-29 region of rat amylin (rIAPP) in which the arginine residue at position 18 was substituted by a histidine residue was also obtained to assess that the PEG moiety does not alter the peptide secondary structure. The complex species formed by Cu(2+) ions with Ac-PEG-hIAPP(17-29)-NH2 , Ac-rIAPP(17-29)R18H-NH2 , and Ac-PEG-hIAPP(14-22)-NH2 were studied by using potentiometric titrations coupled with spectroscopic methods (UV/Vis, circular dichroism, and EPR). The combined thermodynamic and spectroscopic approach allowed us to demonstrate that hIAPP is able to bind Cu(2+) ions starting from the His18 imidazole nitrogen atom toward the N-terminus domain. The stability constants of copper(II) complexes with Ac-PEG-hIAPP(14-22)-NH2 were used to simulate the different experimental conditions under which aggregate formation and oxidative stress of hIAPP has been reported. Speciation unveils: 1) the protective role played by increased amounts of Cu(2+) ions on the hIAPP fibrillary aggregation, 2) the effect of adventitious trace amounts of Cu(2+) ions present in phosphate-buffered saline (PBS), and 3) a reducing fluorogenic probe on H2 O2 production attributed to the polypeptide alone.

Three stable copper complexes of peptides derived from the copper ion binding loop of the subunit II of cytochrome c oxidase have been prepared and characterized by various spectroscopic techniques. These stable copper complexes of peptides were found to exhibit cysteine, histidine and/or methionine ligation, which has predominant σ-contribution in the Cys-Cu charge transfer. The copper(ii) peptide complexes showed type-2 EPR spectra, which is uncommon in copper-cysteinate complexes. UV-visible spectra, Raman and EPR results support a tetragonal structure of the coordination geometry around the copper ion. The copper complex of the 9-amino acid peptide suggested the formation of a 'red' copper center while the copper complexes of the 12- and 11-amino acid peptides showed the formation of a 'green' copper center. The results provide insights on the first stable models of the copper complexes formed in the peptide scaffold that mimic the mono-nuclear copper bound protein intermediates proposed during the formation of the binuclear Cu2S2 core of the enzyme. These three copper complexes of peptides derived from the metal ion binding loop of the CuA center of the subunit II of cytochrome c oxidase showed novel spectroscopic properties which have not so far been reported in any stable small complex.

Porous ion-exchange resins with features of high selectivity, high capacity, fast adsorption kinetics and chemical stability over a wide pH range are attractive for extracting precious metals like copper and upcycling waste. In this study, porous glutaraldehyde-polyethyleneimine (GA-PEI) particulate resin was synthesised using diatomaceous earth (DE) particles as a bio-template. The crosslinking of PEI by GA was successfully conducted on the surface of DE. Removal of the template DE, merely by chemical etching with potassium hydroxide, resulted in the porous GA-PEI particulate resin. The resin showed excellent selectivity for copper ions in binding and recovery from solutions as complex as real legacy acid mine drainage liquid. The copper ion uptake capacity of the GA-PEI resin was determined to be > 8 times greater than non-etched GA-PEI-DE particles. Under the investigated conditions, the GA-PEI resin showed higher selectivity to copper ions from real legacy acid mine drainage liquid compared to the commercial resins Purolite S930 Plus and Lewatit TP 220. Importantly, the absorbed copper ions could be released by simply adjusting pH of the solution to 1. For uptake from acid mine drainage liquid at pH 4 and elution at pH 1, purer copper solutions were achieved with GA-PEI compared to Purolite S930 Plus or Lewatit TP 220 following two cycles of iteration. The results indicate the great potential for using the porous GA-PEI resin in copper extraction under real-world conditions. Refereed/Peer-reviewed

MicroRNA528 (miR528) is a conserved monocot-specific small RNA that has the potential of mediating multiple stress responses. So far, however, experimental functional studies of miR528 are lacking. Here, we report that overexpression of a rice (Oryza sativa) miR528 (Osa-miR528) in transgenic creeping bentgrass (Agrostis stolonifera) alters plant development and improves plant salt stress and nitrogen (N) deficiency tolerance. Morphologically, miR528-overexpressing transgenic plants display shortened internodes, increased tiller number, and upright growth. Improved salt stress resistance is associated with increased water retention, cell membrane integrity, chlorophyll content, capacity for maintaining potassium homeostasis, CATALASE activity, and reduced ASCORBIC ACID OXIDASE (AAO) activity; while enhanced tolerance to N deficiency is associated with increased biomass, total N accumulation and chlorophyll synthesis, nitrite reductase activity, and reduced AAO activity. In addition, AsAAO and COPPER ION BINDING PROTEIN1 are identified as two putative targets of miR528 in creeping bentgrass. Both of them respond to salinity and N starvation and are significantly down-regulated in miR528-overexpressing transgenics. Our data establish a key role that miR528 plays in modulating plant growth and development and in the plant response to salinity and N deficiency and indicate the potential of manipulating miR528 in improving plant abiotic stress resistance.

Higher efficacy and safety of nano gold therapeutics require examination of cellular responses to gold nanoparticles (AuNPs). In this work we compared cellular uptake, cytotoxicity and RNA expression patterns induced in Caco-2 cells exposed to AuNP (5 and 30nm). Cellular internalization was dose and time-dependent for both AuNPs. The toxicity was observed by colony forming efficiency (CFE) and not by Trypan blue assay, and exclusively for 5nm AuNPs, starting at the concentration of 200μM (24 and 72h of exposure). The most pronounced changes in gene expression (Agilent microarrays) were detected at 72h (300μM) of exposure to AuNPs (5nm). The biological processes affected by smaller AuNPs were: RNA/zinc ion/transition metal ion binding (decreased), cadmium/copper ion binding and glutathione metabolism (increased). Some Nrf2 responsive genes (several metallothioneins, HMOX, G6PD, OSGIN1 and GPX2) were highly up regulated. Members of the selenoproteins were also differentially expressed. Our findings indicate that exposure to high concentration of AuNPs (5nm) induces metal exposure, oxidative stress signaling pathways, and might influence selenium homeostasis. Some of detected cellular responses might be explored as potential enhancers of anti-cancer properties of AuNPs based nanomedicines.

Background Transcription factors (TFs) and microRNAs (miRNAs) are primary gene regulators within the cell. Regulatory mechanisms of these two main regulators are of great interest to biologists and may provide insights into the abiotic and biotic stresses. However, the interaction between miRNAs and TFs in a gene regulatory network (GRN) still remains uncovered. Previous research has been mostly directed at inferring either miRNA or TF regulatory networks from data. However, networks involving a single type of regulator may not fully reveal the complex gene regulatory mechanisms, therefore study of interplay among these two regulators in gene regulation is important towards explaining the mechanism of different abiotic stresses. Result Oligonucleotide microarrays containing 51,279 transcripts were used to identify total 133 salt responsive target genes regulated by 11 TFs that are also differentially regulated by miRNA under salinity, heat and drought stresses in Oryza sativa. TF's-target interactions which are most enriched in their downstream regulation were also identified. Many genes whose encoded proteins are implicated in response to light and radiation stimulus, hormone stimuli, oxidative stress, copper ion binding and electron transport were found to be enriched. However the majority were novel for the combined abiotic stress, which indicates that there are a great number of genes induced after the exposure these abiotic stresses and regulated by miRNA. Conclusion Analysis of the expression profile data of Oryza provides clues regarding some putative cellular and molecular processes that are undertaken in response to these stresses. The study also identified a large number of candidate functional genes that appear to be constitutively involved in salt, drought and heat stresses tolerance. Further examination of these genes may enable the molecular basis of abiotic stress tolerance in Oryza, to be elucidated.

Metals are essential to all organisms; accordingly, cells employ numerous genes to maintain metal homeostasis as high levels can be toxic. In the present study, the gene operons responsive to metal(loid)s were employed to generate bacterial cell-based biosensors to detect target metal(loid)s. The cluster of genes related to copper transport known as the cop-operon is regulated by the interaction between the copA promoter region (copAp) and CueR, turning on and off gene expression upon copper ion binding. Therefore, the detection of copper ions could be achieved by inserting a plasmid harboring the fusion of copAp and reporter genes, such as enzymes and fluorescent genes. However, copAp is not as strong a promoter as other metal-inducible promoters, such as znt-, mer-, and ars-operons; thereby, its sensitivity toward copper ions was not sufficient for quantification. To overcome this problem, we engineered Escherichia coli with a deletion of copA to interfere with copper export from cells. The engineered E. coli whole-cell bioreporter was able to detect copper ions at 0 to 10 μM in an aqueous solution. Most importantly, it was specific to copper among several tested heavy metal(loid)s. Therefore, it will likely be useful to detect copper in diverse environmental systems. Although additional improvements are still required to optimize the E. coli-based copper-sensing whole-cell bioreporters presented in this study, our results suggest that there is huge potential to generate whole-cell bioreporters for additional targets by molecular engineering.

Seed maturation and embryogenesis in plants are crucial event for food production of all human beings. Delayed seed maturation and abnormal embryo formation of food crops degrade the quality and quantity of food grains. By performing comparative gene analysis of different microarray experiments in different stages of embryogenesis in Arabidopsis thaliana, using as model plant, here the authors identified a gene coexpression module in preglobular stage. In this module, different genes have been studied which are over-expressed during embryogenesis related with several KEGG metabolic pathways. Analysing the gene cluster evolved from network we concluded that microRNA regulates gene expression of two genes. One of them NRMP6, a metal ion transporter protein gene and second one SKS8, has copper ion binding activity, are regulated by miR167A/B. Since these two genes are also expressed during embryogenesis of other food crops e.g. rice tomato etc, so the microRNAs regulation on gene expression during embryogenesis can be extrapolated for other economically important seeds.

In this paper we present the studies on coordination abilities of multi-His analogue of somatostatin. The somatostatin is a peptide hormone of which radionuclide-labeled analogues are successfully used in clinical practice in receptor scintigraphy. Its the analogue presented in this study is characterized by the presence of four His residues located in groups of two at both ends of the peptide. The -PheTrpLysThr- fragment placed between His residues is responsible for the spatial arrangement which determines the interaction with somatostatin receptors. In this paper we present the impact of copper ion binding on the spatial arrangement of the crucial fragment of peptide. The analysis of potentiometric and spectroscopic data allowed us to characterize the coordination abilities of the peptide and show that the ligand forms a {4×N Im } complex in the physiological range of pH. Results of the molecular modeling gave an insight into the structural aspects of this complex.

A macrocyclic ring comprising multiple hydrogen-bonding sites as well as metal-chelating sites is shown to play the role of ligand in active templated, copper-catalysed [2]rotaxane formation via Huisgen and Glaser reactions. The crystallographic structure and copper ion binding studies are provided for the free macrocycle, along with molecular modelling, barbital, N,N′-trimethyleneurea and copper (I) binding information for the new rotaxanes.

The classical force field, which is compatible with the Amber force field 99SB, has been obtained for the interaction of Cu(II) with monomer and dimers of amyloid-? peptides using the coordination where Cu(II) is bound to His6, His13 (or His14), and Asp1 with distorted planar geometry. The newly developed force field and molecular dynamics simulation were employed to study the impact of Cu(II) binding on structures and dynamics of A? 42 monomer and dimers. It was shown that in the presence of Cu(II) the ? content of monomer is reduced substantially compared with the wild-type A? 42 suggesting that, in accord with experiments, metal ions facilitate formation of amorphous aggregates rather than amyloid fibrils with cross-? structures. In addition, one possible mechanism for amorphous assembly is that the Asp23-Lys28 salt bridge, which plays a crucial role in ? sheet formation, becomes more flexible upon copper ion binding to the A? N-terminus. The simulation of dimers was conducted with the Cu(II)/A? stoichiometric ratios of 1:1 and 1:2. For the 1:1 ratio Cu(II) delays the A? dimerization process as observed in a number of experiments. The mechanism underlying this phenomenon is associated with slow formation of interchain salt bridges in dimer as well as with decreased hydrophobicity of monomer upon Cu-binding.

The three dimensional atomic structures of proteins provide information regarding their function; and codified relationships between structure and function enable the assessment of function from structure. In the current study, a new data mining tool was implemented that checks current gene ontology (GO) annotations and predicts new ones across all the protein structures available in the Protein Data Bank (PDB). The tool overcomes some of the challenges of utilizing large amounts of protein annotation and measurement information to form correspondences between protein structure and function. Protein attributes were extracted from the Structural Biology Knowledgebase and open source biological databases. Based on the presence or absence of a given set of attributes, a given protein’s functional annotations were inferred. The results show that attributes derived from the three dimensional structures of proteins enhanced predictions over that using attributes only derived from primary amino acid sequence. Some predictions reflected known but not completely documented GO annotations. For example, predictions for the GO term for copper ion binding reflected used information a copper ion was known to interact with the protein based on information in a ligand interaction database. Other predictions were novel and require further experimental validation. These include predictions for proteins labeled as unknown function in the PDB. Two examples are a role in the regulation of transcription for the protein AF1396 from Archaeoglobus fulgidus and a role in RNA metabolism for the protein psuG from Thermotoga maritima. Electronic supplementary material The online version of this article (doi:10.1007/s10969-011-9105-3) contains supplementary material, which is available to authorized users.

It has been hypothesized in this journal and elsewhere, based on surveys of published data from prebiotic synthesis experiments and carbonaceous meteorite analyses, that basic amino acids such as lysine and arginine were not abundant on prebiotic Earth. If the basic amino acids were incorporated only rarely into the first peptides formed in that environment, it is important to understand what protobiotic chemistry is possible in their absence. As an initial test of the hypothesis that basic amino acid negative [BAA(-)] proteins could have performed at least a subset of protobiotic chemistry, the current work reports on a survey of 13 archaeal and 13 bacterial genomes that has identified 61 modern gene sequences coding for known or putative proteins not containing arginine or lysine. Eleven of the sequences found code for proteins whose functions are well known and important in the biochemistry of modern microbial life: lysine biosynthesis protein LysW, arginine cluster proteins, copper ion binding proteins, bacterial flagellar proteins, and PE or PPE family proteins. These data indicate that the lack of basic amino acids does not prevent peptides or proteins from serving useful structural and biochemical functions. However, as would be predicted from fundamental physicochemical principles, we see no fossil evidence of prebiotic BAA(-) peptide sequences capable of interacting directly with nucleic acids.

International audience; Methanobactins (mb) are low-molecular mass, copper-binding molecules secreted by most methanotrophic bacteria. These molecules have been identified for a number of methanotrophs, but only the one produced by Methylosinus trichosporium OB3b (mb-OB3b) has to date been chemically characterized. Here we report the chemical characterization and copper binding properties of a second methanobactin, which is produced by Methylocystis strain SB2 (mb-SB2). mb-SB2 shows some significant similarities to mb-OB3b, including its spectral and metal binding properties, and its ability to bind and reduce Cu(II) to Cu(I). Like mb-OB3b, mb-SB2 contains two five-member heterocyclic rings with associated enethiol groups, which together form the copper ion binding site. mb-SB2 also displays some significant differences compared to mb-OB3b, including the number and types of amino acids used to complete the structure of the molecule, the presence of an imidazolone ring in place of one of the oxazolone rings found in mb-OB3b, and the presence of a sulfate group not found in mb-OB3b. The sulfate is bonded to a threonine-like side chain that is associated with one of the heterocyclic rings and may represent the first example of this type of sulfate group found in a bacterially derived peptide. Acid-catalyzed hydrolysis and decarboxylation of the oxazolone rings found in mb-OB3b and mb-SB2 produce pairs of amino acid residues and suggest that both mb-OB3b and mb-SB2 are derived from peptides. In support of this, the gene for a ribosomally produced peptide precursor for mb-OB3b has been identified in the genome of M. trichosporium OB3b. The gene sequence indicates that the oxazolone rings in mb-OB3b are derived from the combination of a cysteine residue and the carbonyl from the preceding residue in the peptide sequence. Taken together, the results suggest methanobactins make up a structurally diverse group of ribosomally produced, peptide-derived molecules, which share a common pair of five-member rings with associated enethiol groups that are able to bind, reduce, and stabilize copper ions in an aqueous environment.

A Thermodynamic study on the interaction Jack bean urease, JBU, with Cu2+ ion was studied by isothermal titration calorimetry (ITC) at 300 and 310 K in 30 mM Tris buffer solution, pH 7.0. The heats of JBU + Cu2+ interactions are reported and analyzed in terms of the extended solvation theory. It was indicated that there are a set of 12 identical and non-cooperative sites for Cu2+ ion. The binding of Cu2+ ion with JBU is exothermic with dissociation equilibrium constants of 284.883 and 345.855 μM at 300 and 310 K, respectively.

In this article, we report for the first time on the copper (Cu 2+ ) binding characteristics of the far-red fluorescent protein, HcRed, and its application in the development of a reagentless sensing system for copper. The far-red emission of HcRed (λ max = 645 nm) where background cellular fluorescence is low should prove to be advantageous in the development of the sensing system. In the studies performed in our laboratory, we found that the fluorescence of HcRed is quenched in the presence of copper ions (Cu 2+ ). The results obtained through UV-visible and circular dichroism spectra generated in the presence and absence of copper, as well as Stern–Volmer plots at different temperatures, indicate static quenching of HcRed fluorescence in the presence of copper, possibly through the formation of a copper–protein complex. On the basis of this observation, we developed a reagentless sensing system for the detection of copper(II) based on HcRed as the biosensing element. A detection limit for Cu 2+ in the nanomolar range was obtained. HcRed was found to bind copper ions selectively when compared with other divalent ions. A dissociation constant of 3.6 μM was observed for copper binding. Histidine and cysteine residues are commonly involved in copper binding within proteins; therefore, to investigate the role of these amino acids present in HcRed, we chemically modified Cys and His residues using iodoacetamide and diethyl pyrocarbonate, respectively. The effect of copper addition on the fluorescence of the chemically modified HcRed was investigated. The His modification of HcRed substantially affected copper ion binding, pointing to histidine as the possible amino acid residue involved in the binding of copper ions in HcRed. A purification strategy for HcRed was also developed based on a copper immobilized affinity column without the addition of any affinity tag on the protein. The HcRed-based copper sensing system can potentially be employed to perform intracellular copper detection by genetically encoding the biosensing element or can be employed in environmental sensing.

The co-ordination chemistry of some new oxamides towards Cu(II) ions was studied using various techniques: potentiometry, voltammetry, spectroscopy (UV–Vis, CD and EPR) and ESI–MS spectrometry. All tested compounds chelate the copper(II) ions with formation of 1:1 and 1:2 (metal-to-ligand ratio) complexes. The Cu(II) ions are bound by 1N, 2N or 3N nitrogen donor systems. Additionally, an unusual co-ordination to amide N-atoms without additional anchoring site is suggested. The 14N hyperfine splitting observed for the system ox6–Cu(II) above pH 10 clearly indicates the involvement of at least three N donor atoms in the copper ion binding. Moreover, the surrounding by three amide-N and one carbonyl-O stabilizes the high oxidation state of copper(III), although such complexes are very unstable in solution.

Proton binding properties of humic and fulvic acids were studied by potentiometric titration. Carboxylic groups were the predominant ionizable sites in comparison to phenolic and amine groups. Total acidity of fulvic acid was 12 x 10-3 mol g-1, a number significantly higher than that obtained for humic acid (5.2 x 10-3 mol g-1). Copper ion binding was evaluated at pH 4, 5 and 6 by potentiometric titration with an ion selective electrode for Cu(II). Differential stability constants and complexation capacities were systematically higher for humic acid, despite its lower number of ionizable sites in comparison with fulvic acid.

Multicopper oxidases (MCOs) are enzymes that contain 10 conserved histidine residues and 1 cysteine residue. MCO1 has been extensively investigated in the midgut because this MCO is implicated in ascorbate oxidation, iron homeostasis and immune responses. However, information regarding the action of MCO1 in Malpighian tubules is limited. In this study, Helicoverpa armigera was used as a model to investigate the function of MCO1 in Malpighian tubules. Sequence analysis results revealed that HaMCO1 exhibits typical MCO characteristics, with 10 histidine and 1 cysteine residues for copper ion binding. HaMCO1 was also found to be highly abundant in Malpighian tubules. Temporal expression patterns indicated that HaMCO1 is mainly expressed during larval molting stages. Hormone treatments [the molting hormone 20-hydroxyecdysone (20E) and juvenile hormone (JH)] revealed that 20E inhibits HaMCO1 transcript expression via its heterodimer receptor, which consists of ecdysone receptor (EcR) and ultraspiracle (USP) and that JH counteracts the action of 20E to activate HaMCO1 transcript expression via its intracellular receptor methoprene-tolerant (Met). HaMCO1 knockdown caused a significant decrease in iron accumulation and also significantly reduced transferrin and ferritin transcript expression. Therefore, HaMCO1 is coordinately regulated by 20E and JH and is required for iron homeostasis in Malpighian tubules.

The hypothesis that copper modulates the activity of intracellular signal transduction pathways to affect transcription, which ultimately disrupts normal development was investigated. Preliminary analysis of transcriptomes from HepG2 cells exposed to copper for 4 and 24 h identified 19 and 7 up-regulated genes (twofold; p ≤ 0.05), respectively. Among the up-regulated genes, several have been previously reported to be responsive to metals or oxidative stress. Differentially expressed genes were grouped by the functional categories based on gene ontology (GO). Significantly enriched GO categories (p < 0.01) included copper ion homeostasis, cadmium and copper ion binding, and heme oxygenase and oxidoreductase activities. Real-time RT-PCR confirmed the effect of copper on the levels of MT2A, HSPA1A, CYP1A1 and HMOX1 expression.

The function of human Sco1 and Sco2 is shown to be dependent on copper ion binding. Expression of soluble domains of human Sco1 and Sco2 either in bacteria or the yeast cytoplasm resulted in the recovery of copper-containing proteins. The metallation of human Sco1, but not Sco2, when expressed in the yeast cytoplasm is dependent on the co-expression of human Cox17. Two conserved cysteines and a histidyl residue, known to be important for both copper binding and in vivo function in yeast Sco1, are also critical for in vivo function of human Sco1 and Sco2. Human and yeast Sco proteins can bind either a single Cu(I) or Cu(II) ion. The Cu(II) site yields S-Cu(II) charge transfer transitions that are not bleached by weak reductants or chelators. The Cu(I) site exhibits trigonal geometry, whereas the Cu(II) site resembles a type II Cu(II) site with a higher coordination number. To identify additional potential ligands for the Cu(II) site, a series of mutant proteins with substitutions in conserved residues in the vicinity of the Cu(I) site were examined. Mutation of several conserved carboxylates did not alter either in vivo function or the presence of the Cu(II) chromophore. In contrast, replacement of Asp238 in human or yeast Sco1 abrogated the Cu(II) visible transitions and in yeast Sco1 attenuated Cu(II), but not Cu(I), binding. Both the mutant yeast and human proteins were nonfunctional, suggesting the importance of this aspartate for normal function. Taken together, these data suggest that both Cu(I) and Cu(II) binding are critical for normal Sco function.

The formation of weak polyelectrolyte films on planar and spherical supports has recently evoked major interest, as such coatings allow novel material properties to be tunable by pH and salt adjustment of the polyelectrolyte deposition conditions. We report on the build up of multilayers of the weak polyelectrolytes poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) on submicrometer-sized polystyrene (PS) and silica colloid spheres (∼ 500 nm) with the aid of copper ion templating. The copper ions complex to the carboxylate groups of PAA, facilitating the formation of PAA/PAH multilayers on the particles. Regular growth of the layers on the colloid spheres with each polyelectrolyte deposition step was confirmed by microelectrophoresis, single-particle light scattering (SPLS), and transmission electron microscopy (TEM), with an average bilayer thickness of ∼ 3 nm. The polyelectrolyte multilayer-coated particles formed stable colloidal dispersions, with ζ-potentials ranging from 30 mV (PAH outer layer) and –50 mV (PAA outer layer). Complementary quartz-crystal microbalance and UV-vis spectrophotometry studies on PAA/PAH multilayers formed on planar supports were performed to examine the film formation and the role of copper ion binding to the layers. PAA/PAH multilayers formed on colloid particles were also chemically crosslinked by using the activator 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). The degree of film crosslinking could be readily controlled by varying the concentration of EDC employed. Following solvent decomposition of the template particles coated with crosslinked PAA/PAH multilayers, intact hollow polymer capsules were obtained. These capsules were found to be impenetrable to polystyrene.

Modification of soybean hulls with citric acid (CA) improves the metal ion binding capacity of the hulls. A process for this modification has been developed. However, the process must be optimized for it to be cost effective. In this regard, the objectives of this study were (1) to develop a wash procedure to remove non-reacted or residual CA after soybean hull modification in order to maximize the amount of non-reacted acid removed, but minimize the subsequent effect on the product's ability to adsorb copper ion (Cu2+), and (2) to determine whether recycling non-reacted acid in the modification process, along with unused acid, can produce a product with similar copper ion adsorption compared with the use of unused acid only. To meet these objectives, an effective water washing procedure was developed to remove the residual CA associated with the modified soybean hulls. This washing procedure included removal of non-reacted acid, evaporation of excess water to the original volume of acid solution used, and addition of unused CA to reconstitute the solution to its original molarity. Reconstituted CA solutions prepared in this manner were used through three cycles of soybean hull modification. The effectiveness of the reconstituted CA to modify soybean hulls after each cycle was measured by the modified hulls ability to bind copper ions in solution. After three reaction cycles, there was a 7% reduction in copper ion adsorption. In general, two water wash cycles were necessary to remove sufficient non-reacted CA so that metal ion binding of the hulls was not affected, and the use of residual CA to modify soybean hulls can be successfully accomplished with only a small reduction in copper ion binding.

Contains fulltext : 252444.pdf (Publisher’s version ) (Closed access) Prion protein (PrP) sequences are until now available for only six of the 18 orders of placental mammals. A broader comparison of mammalian prions might help to understand the enigmatic functional and pathogenic properties of this protein. We therefore determined PrP coding sequences in 26 mammalian species to include all placental orders and major subordinal groups. Glycosylation sites, cysteines forming a disulfide bridge, and a hydrophobic transmembrane region are perfectly conserved. Also, the sequences responsible for secondary structure elements, for N- and C-terminal processing of the precursor protein, and for attachment of the glycosyl-phosphatidylinositol membrane anchor are well conserved. The N-terminal region of PrP generally contains five or six repeats of the sequence P(Q/H)GGG(G/-)WGQ, but alleles with two, four, and seven repeats were observed in some species. This suggests, together with the pattern of amino acid replacements in these repeats, the regular occurrence of repeat expansion and contraction. Histidines implicated in copper ion binding and a proline involved in 4-hydroxylation are lacking in some species, which questions their importance for normal functioning of cellular PrP. The finding in certain species of two or seven repeats, and of amino acid substitutions that have been related to human prion diseases, challenges the relevance of such mutations for prion pathology. The gene tree deduced from the PrP sequences largely agrees with the species tree, indicating that no major deviations occurred in the evolution of the prion gene in different placental lineages. In one species, the anteater, a prion pseudogene was present in addition to the active gene.

S100A5 is a novel member of the EF-hand superfamily of calcium-binding proteins that is poorly characterized at the protein level. Immunohistochemical analysis demonstrates that it is expressed in very restricted regions of the adult brain. Here we characterized the human recombinant S100A5, especially its interaction with Ca(2+), Zn(2+), and Cu(2+). Flow dialysis revealed that the homodimeric S100A5 binds four Ca(2+) ions with strong positive cooperativity and an affinity 20-100-fold higher than the other S100 proteins studied under identical conditions. S100A5 also binds two Zn(2+) ions and four Cu(2+) ions per dimer. Cu(2+) binding strongly impairs the binding of Ca(2+); however, none of these ions change the alpha-helical-rich secondary structure. After covalent labeling of an exposed thiol with 2-(4'-(iodoacetamide)anilino)-naphthalene-6-sulfonic acid, binding of Cu(2+), but not of Ca(2+) or Zn(2+), strongly decreased its fluorescence. In light of the three-dimensional structure of S100 proteins, our data suggest that in each subunit the single Zn(2+) site is located at the opposite side of the EF-hands. The two Cu(2+)-binding sites likely share ligands of the EF-hands. The potential role of S100A5 in copper homeostasis is discussed.

Coagulation factor VIII (FVIII) is a heterodimer consisting of a light chain of 80 kDa (domains A3-C1-C2) in a metal ion-dependent association with a 220-kDa heavy chain (domains A1-A2-B). The nature of the metal ion-dependent association between the heavy and light chains was investigated using atomic absorption spectroscopy, electron paramagnetic resonance spectroscopy (EPR), and site-directed mutagenesis and expression of the FVIII cDNA. Whereas copper ion was not detected in intact recombinant FVIII, EDTA dissociation of the chains yielded an EPR signal consistent with 1 mol of Cu(I)/mol of active protein, supporting the hypothesis that a single molecule of reduced copper ion is buried within intact FVIII and is released and oxidized upon treatment with EDTA. Cu(I), and not Cu(II), was able to reconstitute FVIII activity from dissociated chains, demonstrating a requirement for Cu(I) in FVIII function. Three potential copper ion binding sites exist within FVIII: one type-2 site and two type-1 sites. The importance of these potential copper ion ligands was tested by studying the effect of site-directed mutants. Of the two histidines that compose the type-2 binding site, the His-1957 --Ala mutant displayed secretion, light and heavy chain assembly, and activity similar to wild-type FVIII, while mutant His-99 --Ala was partially defective for secretion and had low levels of heavy and light chain association and activity. In contrast, FVIII having the mutation Cys-310 --Ser within the type-1 copper binding site in the A1 domain was inactive and partially defective for secretion from the cell, and the heavy and light chains of the secreted protein were not associated. Mutant Cys-2000 --Ser within the A3 domain displayed secretion, assembly, and activity similar to that for wild-type FVIII. These results support the hypothesis that Cu(I) is buried within the type-1 copper binding site within the A1 domain and is required for FVIII chain association and activity.

Preliminary screening laboratory batch experiments to determine the binding ability of seven different populations of Medicago sativa (alfalfa) showed good copper binding characteristics of the biomasses studied. All seven populations examined had similar trends for binding copper as a function of pH. The copper binding by the different alfalfa populations occurred within 5 min. All the alfalfa biomasses showed high copper binding, but the capacities varied according to the alfalfa sample studied. The pH dependence of the copper ion binding to the alfalfa biomasses suggested that it might be possible to recycle the system much like an ion-exchange resin. However, the alfalfa cells cannot be packed into a column because the cells clump together and restrict the flow. We immobilized the cells of Malone alfalfa shoots in a silica matrix. Column experiments for copper binding by the silica immobilized alfalfa demonstrated that the alfalfa tissues were capable of removing considerable amounts of copper ions under flow conditions. After every copper binding cycle most of the copper was desorbed with a few bed volumes of 0.1 M HCl. Our work indicates that the Malone-silica preparations are highly durable. We subjected the biomaterial to as many as 10 cycles of binding and elution without observing any significant decrease in copper binding capacity.

In the research conducted the complexation of Cu/sup 2 +/ by an Armadale Horizons Bh fulvic acid sample was studied to facilitate the program. The use of literature-based stability constants for the Cu/sup 2 +/ ion complexes species formed with the different sites deduced from the design of the experimental program led to a capability for predicting the binding of macro quantities of Cu(II) to Armadale Horizon Bh fulvic acid as a function of degree of neutralization, ionic strength, and metal ion and fulvic acid concentration. The predictive quality provided by such assignment of binding parameters is felt to provide strong corroborative support for the deduced site assignments and thus for the model itself. 10 references, 6 figures, 5 tables.

The closed, isolated small systems, as the representatives of a “unique environmental feature”, are valuable natural laboratories for studying different biogeochemical processes. Saline Rogoznica Lake (“Dragon Eye”), situated on the Eastern Adriatic coast is such a system (10276 m2, 15 m deep) typical for many stratified, sulfide rich water bodies. The depth of mixolimnion changes seasonally and it is greatly influenced by meteorological conditions, i.e. temperature and rainfall. Vertical mixing usually occurs during winter when cold, oxygen-rich water from the surface sinks downwards. In 2009 we monitored seasonal distribution and variation of copper complexing capacity (LT), related apparent stability constants (Kapp), concentration of Cu2+ ions, surfactant activity (SAS), dissolved organic carbon (DOC) and reduced sulfur species (RSS). Our results have shown that LT is increasing with depth up to 8 m depth, while the concentrations of copper ions decrease with the depth due to the higher amount of RSS species in deeper layers. The values of log Kapp are also decreasing with depth as a consequence of a competition of organic ligands and sulfide ions for binding Cu. Below 8m depth the presence of high amounts of RSS (~1mM) influence the electrochemical measuring of copper ion and LT determination, contributing to the copper ion binding.

The binding of copper ion to the surfaces of the marine diatom Phaeodactylum tricornutum was studied in seawater pH 8. The cell wall complexing capacity and the average surface complex formation constant were determined by voltammetric titration curves. The presence of biotic particles at a concentration of 2.7 X 106 cells mL−1 does not hinder the measurement of stripping currents and the voltammetric fraction of non-reducible copper is the same as the copper bound to the cell surfaces as measured by atomic absorption spectrometry.

Background MicroRNAs (miRNAs) play a critical role in post-transcriptional gene regulation and have been shown to control many genes involved in various biological and metabolic processes. There have been extensive studies to discover miRNAs and analyze their functions in model plant species, such as Arabidopsis and rice. Deep sequencing technologies have facilitated identification of species-specific or lowly expressed as well as conserved or highly expressed miRNAs in plants. Results In this research, we used Solexa sequencing to discover new microRNAs in trifoliate orange (Citrus trifoliata) which is an important rootstock of citrus. A total of 13,106,753 reads representing 4,876,395 distinct sequences were obtained from a short RNA library generated from small RNA extracted from C. trifoliata flower and fruit tissues. Based on sequence similarity and hairpin structure prediction, we found that 156,639 reads representing 63 sequences from 42 highly conserved miRNA families, have perfect matches to known miRNAs. We also identified 10 novel miRNA candidates whose precursors were all potentially generated from citrus ESTs. In addition, five miRNA* sequences were also sequenced. These sequences had not been earlier described in other plant species and accumulation of the 10 novel miRNAs were confirmed by qRT-PCR analysis. Potential target genes were predicted for most conserved and novel miRNAs. Moreover, four target genes including one encoding IRX12 copper ion binding/oxidoreductase and three genes encoding NB-LRR disease resistance protein have been experimentally verified by detection of the miRNA-mediated mRNA cleavage in C. trifoliata. Conclusion Deep sequencing of short RNAs from C. trifoliata flowers and fruits identified 10 new potential miRNAs and 42 highly conserved miRNA families, indicating that specific miRNAs exist in C. trifoliata. These results show that regulatory miRNAs exist in agronomically important trifoliate orange and may play an important role in citrus growth, development, and response to disease.

Our continuing efforts into developing copper coordination chemistry relevant to dioxygen-processing copper proteins has led us to design and synthesize a cyclotriveratrylene (CTV)-based trinucleating ligand, CTV-TMPA, which employs tetradentate tris(2-pyridylmethyl)-amine chelates (TMPA) for their copper ion binding sites. Binding of three copper ions per CTV-TMPA unit was established by various chemical and spectroscopic methods such as UV-vis and resonance Raman (rR) spectroscopies. The following complexes were observed: A tricopper(I) complex [(CTV-TMPA)Cu(I)(3)](3+) (1), a CO adduct [(CTV-TMPA)Cu(I)(3)(CO)(3)](3+) (1-CO; nu(C=O) = 2094 cm(-1)), a triphenylphosphine adduct [(CTV-TMPA)Cu(I)(3)(PPh(3))(3)](3+) (1-PPh(3)), a tricopper(II) complex [(CTV-TMPA)Cu(II)(3)](3+) (1-Ox), and its tris-monochloride or tris-monobromide adducts. Also, introduction of dioxygen to the -80 degrees C solutions of 1 leads to O(2)-adducts, the first example of a synthetic copper complex which can stabilize a mononuclear Cu(II)-superoxo and dinuclear peroxo species simultaneously within one complex {[Cu] = 1.53 mM in THF: (mu-1,2-peroxo complex, lambda(max) = 543 (epsilon 9650) nm): nu(O-O) = 825 ((Delta(18)O(2)) = -47) cm(-1); nu(Cu-O) = 506 ((Delta(18)O(2)) = -26) cm(-1): (superoxo complex, lambda(max) = 427 (epsilon 3150) nm): nu(O-O) = 1129 ((Delta(18)O(2)) = -60) cm(-1); nu(Cu-O) = 463 ((Delta(18)O(2)) = -27) cm(-1)}. Elemental sulfur reacts reversibly with 1 leading to a (proposed) hexanuclear species [{(CTV-TMPA)Cu(II)(3)}(2)(mu-1,2-S(2)(2-))(3)](6+) (1-S) {lambda(max) = 544 (epsilon 7270) nm}, possessing one dicopper(II)-disulfide structural type: {THF solvent) nu(S-S) = 489 ((Delta(34)S) = -10) cm(-1); nu(Cu-S) = 307 ((Delta(34)S) = -5) cm(-1)}. Derivation of spectroscopic, structural, and chemical conclusions were aided by the study of a close mononuclear analogue with one pyridyl group of the TMPA parent possessing a 6-CH(2)OCH(3) substituent, this being part of the CTV-TMPA architecture.

We present a hybrid QM/MM Car–Parrinello molecular dynamics study of the copper-loaded C-terminal domain of the mouse prion protein. By means of a statistical analysis of copper coordination in known protein structures, we localized the protein regions with the highest propensity for copper ion binding. The identified candidate structures were subsequently refined via QM/MM simulations. Their EPR characteristics were computed to make contact with the experimental data and to probe the sensitivity to structural and chemical changes. Overall best agreement with the experimental EPR data (Van Doorslaer et al., J Phys Chem B 2001; 105: 1631–1639) and the information currently available in the literature is observed for a binding site involving H187. Moreover, a reinterpretation of the experimental proton hyperfine couplings was possible in the light of the present computational findings. Proteins 2008. © 2007 Wiley-Liss, Inc.

Cupric ion fixation by raw peat is likely involved in both cation exchange with H+, Ca2+, Mg2+ and adsorption-complexation, i.e. fixation of the same equivalent of copper ions and anions (NO3−) without any ion release. The importance of both reactions depends largely on initial copper concentration, peat type and pH. Isotherms of copper (initial concentration ranging between 1 and 20 mM) fixation on two types of peat (eutrophic and oligotrophic peat at 30 g d.w./l at pH ranging between 2 and 4) showed that the higher the initial cupric concentration, the more important is this complexation reaction; over this initial cupric concentration range, ion exchange sites were relatively saturated and reached 308 and 101 mmol/kg d.w. for eutrophic and oligotrophic peat whereas no saturation was found for complexation sites, their capacity attaining up to 74 and 119 mmol/kg d.w., respectively. The apparent equilibrium constant for ion exchange with acid-treated peat (initial pH 4.0, 30 g d.w./l) for various metal binding on both peat sites ranged between 1.1 and 10.8 in 15 mM metallic solutions. The apparent affinity in batch conditions for 5 elements may be compared according to the apparent global equilibrium constants, ranging between 1.1 × 10−6 and 20.2 × 10−6: Pb > Cu > Ca > Mg, Zn for eutrophic peat and Pb > Ca > Cu > Mg, Zn for oligotrophic peat.

Root samples of 'Sanhu' red tangerine trees infected with and without Candidatus Liberibacter asiaticus (CLas) were collected at 50 days post inoculation and subjected to RNA-sequencing and isobaric tags for relative and absolute quantification (iTRAQ) to profile the differentially expressed genes (DEGs) and proteins (DEPs), respectively. Quantitative real-time PCR was subsequently used to confirm the expression of 16 selected DEGs. Results showed that a total of 3956 genes and 78 proteins were differentially regulated by HLB-infection. Among the most highly up-regulated DEPs were sperm specific protein 411, copper ion binding protein, germin-like proteins, subtilisin-like proteins and serine carboxypeptidase-like 40 proteins whose transcript levels were concomitantly up-regulated as shown by RNA-seq data. Comparison between our results and those of the previously reported showed that known HLB-modulated biological pathways including cell-wall modification, protease-involved protein degradation, carbohydrate metabolism, hormone synthesis and signaling, transcription activities, and stress responses were similarly regulated by HLB infection but different or root-specific changes did exist. The root unique changes included the down-regulation in genes of ubiquitin-dependent protein degradation pathway, secondary metabolism, cytochrome P450s, UDP-glucosyl transferases and pentatricopeptide repeat containing proteins. Notably, nutrient absorption was impaired by HLB-infection as the expression of the genes involved in Fe, Zn, N and P adsorption and transportation were significantly changed. HLB-infection induced some cellular defense responses but simultaneously reduced the biosynthesis of the three major classes of secondary metabolites, many of which are known to have anti-pathogen activities. Genes involved in callose deposition were up-regulated whereas those involved in callose degradation were also up-regulated, indicating that the sieve tube elements in roots were hanging on the balance of life and death at this stage. In addition, signs of carbohydrate starvation were already eminent in roots at this stage. Other interesting genes and pathways that were changed by HLB-infection were also discussed based on our findings.

The centipede Scolopendra subspinipes mutilans L. Koch (‘Wugong’), the beetle Mylabris phalerata Pallas (‘Ban mao’) and the earthworm Pheretima aspergillum Chen (‘DiLong’) have a reputation in traditional Chinese medicine for reducing symptoms of central nervous system decline, including memory loss. A series of extracts of all three organisms was tested for acetylcholinesterase (AChE) inhibition and copper ion binding effects, the latter likely to reduce oxidative damage caused by excess copper. The beetle and centipede chloroform extracts showed the strongest AChE inhibitory effects (30.6% inhibition at 105 μg mL−1 and 32.3% inhibition at 167 μg mL−1, respectively) and, in the case of the centipede, this was traced to the unsaturated fatty acids present using bioassay-guided fractionation. Cantharidin from the beetle was shown to have AChE activity (31% inhibition at 1 μM, 0.196μg mL−1), making it a major contributor to the activity of the beetle extract. The earthworm showed no AChE inhibitory activity. Since unsaturated fatty acids have not been previously reported to have AChE inhibitory activity, a series of related compounds was tested to determine structure-activity relationships. It was found that activity existed where there was a chain length of more than 16 C atoms with at least one unsaturated bond in the chain. The carboxylic acid group was also necessary for activity. The fatty acids present in the centipede also showed the ability to bind copper ions when tested using a novel thin layer chromatography method designed to detect copper-binding compounds. The activities reported give some support to the use of the beetle and centipede in traditional Chinese medicine for improving cognitive function.

Processing of the recycling proteoglycan glypican-1 involves the release of its heparan sulfate chains by copper ion- and nitric oxide-catalyzed ascorbate-triggered autodegradation. The Alzheimer disease amyloid precursor protein (APP) and its paralogue, the amyloid precursor-like protein 2 (APLP2), contain copper ion-, zinc ion-, and heparan sulfate-binding domains. We have investigated the possibility that APP and APLP2 regulate glypican-1 processing during endocytosis and recycling. By using cell-free biochemical experiments, confocal laser immunofluorescence microscopy, and flow cytometry of tissues and cells from wild-type and knock-out mice, we find that (a) APP and glypican-1 colocalize in perinuclear compartments of neuroblastoma cells, (b) ascorbate-triggered nitric oxidecatalyzed glypican-1 autodegradation is zinc ion-dependent in the same cells, (c) in cell-free experiments, APP but not APLP2 stimulates glypican-1 autodegradation in the presence of both Cu(II) and Zn(II) ions, whereas the Cu(I) form of APP and the Cu(II) and Cu(I) forms of APLP2 inhibit autodegradation, (d) in primary cortical neurons from APP or APLP2 knock-out mice, there is an increased nitric oxide-catalyzed degradation of heparan sulfate compared with brain tissue and neurons from wild-type mice, and (e) in growth-quiescent fibroblasts from APLP2 knock-out mice, but not from APP knock-out mice, there is also an increased heparan sulfate degradation. We propose that the rate of autoprocessing of glypican-1 is modulated by APP and APLP2 in neurons and by APLP2 in fibroblasts. These observation identify a functional relationship between the heparan sulfate and copper ion binding activities of APP/APLP2 in their modulation of the nitroxyl anion-catalyzed heparan sulfate degradation in glypican-1.

The conversion of cellular prion protein (PrP C ) into its pathological isoform (PrP S c ) conveys an increase in hydrophobicity and induces a partial resistance to proteinase K (PK). Interestingly, co-incubation with high copper ion concentrations also modifies the solubility of PrP C and induces a partial PK resistance which was reminiscent of PrP S c . However, concerns were raised whether this effect was not due to a copper-induced inhibition of the PK itself. We have therefore analyzed the kinetics of the formation of PK-resistant PrP C and excluded possible interference effects by removing unbound copper ions prior to the addition of PK by methanol precipitation or immobilization of PrP C followed by washing steps. We found that preincubation of PrP C with copper ions at concentrations as low as 50 μM indeed rendered these proteins completely PK resistant, while control substrates were proteolyzed. No other divalent cations induced a similar effect. However, in addition to this specific stabilizing effect on PrP C , higher copper ion concentrations in solution (>200 μM) directly blocked the enzymatic activity of PK, possibly by replacing the Ca 2 + ions in the active center of the enzyme. Therefore, as a result of this inhibition the proteolytic degradation of PrP C as well as PrP S c molecules was suppressed.

Copper ion uptake must be regulated to avoid both deficiency and excess because its essential yet toxic biological nature depends on the concentration. Yeast copper uptake is controlled at both the transcriptional and post-translational levels. The transcription ofCTR1 and CTR3, encoding high affinity copper ion transporters, is regulated by the copper ion-sensing transcription factor Mac1p through the cis-acting copper ion-responsive elements in CTR1 and CTR3 promoters. Ctr1p is known to undergo degradation in cells exposed to high copper levels. We report that Mac1p is also required for copper-dependent Ctr1p degradation. Both mutations within a conserved copper ion binding motif, the “Cu-fist” in the Mac1p DNA-binding domain, and within a metal ion binding motif, REP-III located in the cytosolic domain of Ctr1p, cause defects in Ctr1p turnover. Furthermore, we show that the Mac1p limits intracellular copper accumulation likely by controlling Ctr1p degradation. The findings have uncovered an unprecedented mechanism by which a transcription factor not only regulates its target gene transcription but also controls the degradation of its target gene product.

Human serum paraoxonase (PON1) can protect low density lipoprotein (LDL) from oxidation induced by either copper ion or by the free radical generator azo bis amidinopropane hydrochloride (AAPH). During LDL oxidation in both of these systems, a time-dependent inactivation of PON arylesterase activity was observed. Oxidized LDL (Ox-LDL) produced by lipoprotein incubation with either copper ion or with AAPH, indeed inactivated PON arylesterase activity by up to 47% or 58%, respectively. Three possible mechanisms for PON inactivation during LDL oxidation were considered and investigated: copper ion binding to PON, free radical attack on PON, and/or the effect of lipoprotein-associated peroxides on the enzyme. As both residual copper ion and AAPH are present in the Ox-LDL preparations and could independently inactivate the enzyme, the effect of minimally oxidized (Ox-LDL produced by LDL storage in the air) on PON activity was also examined. Oxidized LDL, as well as oxidized palmitoyl arachidonoyl phosphatidylcholine (PAPC), lysophosphatidylcholine (LPC, which is produced during LDL oxidation by phospholipase A2-like activity), and oxidized cholesteryl arachidonate (Ox-CA), were all potent inactivators of PON arylesterase activity (PON activity was inhibited by 35%-61%). PON treatment with Ox-LDL (but not with native LDL), or with oxidized lipids, inhibited its arylesterase activity and also reduced the ability of the enzyme to protect LDL against oxidation. PON Arylesterase activity however was not inhibited when PON was pretreated with the sulfhydryl blocking agent, p-hydroxymercurybenzoate (PHMB). Similarly, on using recombinant PON in which the enzyme's only free sulfhydryl group at the position of cysteine-284 was mutated, no inactivation of the enzyme arylesterase activity by Ox-LDL could be shown. These results suggest that Ox-LDL inactivation of PON involves the interaction of oxidized lipids in Ox-LDL with the PON's free sulfhydryl group. Antioxidants such as the flavonoids glabridin or quercetin, when present during LDL oxidation in the presence of PON, reduced the amount of lipoprotein-associated lipid peroxides and preserved PON activities, including its ability to hydrolyze Ox-LDL cholesteryl linoleate hydroperoxides. We conclude that PON's ability to protect LDL against oxidation is accompanied by inactivation of the enzyme. PON inactivation results from an interaction between the enzyme free sulfhydryl group and oxidized lipids such as oxidized phospholipids, oxidized cholesteryl ester or lysophosphatidylcholine, which are formed during LDL oxidation. The action of antioxidants and PON on LDL during its oxidation can be of special benefit against atherosclerosis since these agents reduce the accumulation of Ox-LDL by a dual effect: i.e. prevention of its formation, and removal of Ox-LDL associated oxidized lipids which are generated during LDL oxidation.

Low molecular proteins (LMPs) which are smaller than 20 kDa are difficult to visible on a standard two-dimensional SDS-polyacrylamide gel electrophoresis (2-D SDS-PAGE) map. LMPs must be enriched appropriately to be analyzed. We isolated LMPs of Helicobacter pylori 26695 from 1-D polyacrylamide gel and digested by pepsin. Pepsin-digested LMPs were separated by HPLC and each fraction was analyzed by hybrid tandem mass spectrometer. Seventy nine peptides, representing 27 genes, including copper ion binding protein (CopP, 7 kDa), thioredoxin (TrxA, 11.9 kDa) and ribosomal protein L23 (Rpl23, 10.5 kDa) were identified. Some proteins larger than 40 kDa including Omp2, Omp21, Omp27, Omp30, Omp32, catalase and HP1083 were also identified. This work may give researchers a useful way to analyse the expressed LMPs which could not be identified on the conventional 2-D SDS-PAGE.