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1.
Nature ; 2024 Jun 26.
Article in English | MEDLINE | ID: mdl-38926572

ABSTRACT

Chemical reaction networks, such as those found in metabolism and signalling pathways, enable cells to process information from their environment1,2. Current approaches to molecular information processing and computation typically pursue digital computation models and require extensive molecular-level engineering3. Despite considerable advances, these approaches have not reached the level of information processing capabilities seen in living systems. Here we report on the discovery and implementation of a chemical reservoir computer based on the formose reaction4. We demonstrate how this complex, self-organizing chemical reaction network can perform several nonlinear classification tasks in parallel, predict the dynamics of other complex systems and achieve time-series forecasting. This in chemico information processing system provides proof of principle for the emergent computational capabilities of complex chemical reaction networks, paving the way for a new class of biomimetic information processing systems.

2.
J Am Chem Soc ; 145(13): 7559-7568, 2023 Apr 05.
Article in English | MEDLINE | ID: mdl-36961990

ABSTRACT

Prebiotic environments are dynamic, containing a range of periodic and aperiodic variations in reaction conditions. However, the impact of the temporal dynamics of environmental conditions upon prebiotic chemical reaction networks has not been investigated. Here, we demonstrate how the magnitude and rate of temporal fluctuations of the catalysts Ca2+ and hydroxide control the product distributions of the formose reaction. Surprisingly, the product compositions of the formose reaction under dynamic conditions deviate significantly from those under steady state conditions. We attribute these compositional changes to the non-uniform propagation of fluctuations through the network, thereby shaping reaction outcomes. An examination of temporal concentration patterns showed that collections of compounds responded collectively to perturbations, indicating that key gating reactions branching from the Breslow cycle may be important responsive features of the formose reaction. Our findings show how the compositions of prebiotic reaction networks were shaped by sequential environmental events, illustrating the necessity for considering the temporal traits of prebiotic environments that supported the origin of life.

3.
J Am Chem Soc ; 142(28): 12226-12236, 2020 07 15.
Article in English | MEDLINE | ID: mdl-32551568

ABSTRACT

Metal-dependent formate dehydrogenases (FDHs) catalyze the reversible conversion of formate into CO2, a proton, and two electrons. Kinetic studies of FDHs provide key insights into their mechanism of catalysis, relevant as a guide for the development of efficient electrocatalysts for formate oxidation as well as for CO2 capture and utilization. Here, we identify and explain the kinetic isotope effect (KIE) observed for the oxidation of formate and deuterioformate by the Mo-containing FDH from Escherichia coli using three different techniques: steady-state solution kinetic assays, protein film electrochemistry (PFE), and pre-steady-state stopped-flow methods. For each technique, the Mo center of FDH is reoxidized at a different rate following formate oxidation, significantly affecting the observed kinetic behavior and providing three different viewpoints on the KIE. Steady-state turnover in solution, using an artificial electron acceptor, is kinetically limited by diffusional intermolecular electron transfer, masking the KIE. In contrast, interfacial electron transfer in PFE is fast, lifting the electron-transfer rate limitation and manifesting a KIE of 2.44. Pre-steady-state analyses using stopped-flow spectroscopy revealed a KIE of 3 that can be assigned to the C-H bond cleavage step during formate oxidation. We formalize our understanding of FDH catalysis by fitting all the data to a single kinetic model, recreating the condition-dependent shift in rate-limitation of FDH catalysis between active-site chemical catalysis and regenerative electron transfer. Furthermore, our model predicts the steady-state and time-dependent concentrations of catalytic intermediates, providing a valuable framework for the design of future mechanistic experiments.


Subject(s)
Formate Dehydrogenases/metabolism , Formates/metabolism , Carbon Dioxide/chemistry , Carbon Dioxide/metabolism , Catalysis , Crystallography, X-Ray , Formate Dehydrogenases/chemistry , Formates/chemistry , Models, Molecular , Molecular Structure , Oxidation-Reduction
4.
Acc Chem Res ; 52(5): 1439-1448, 2019 05 21.
Article in English | MEDLINE | ID: mdl-31042353

ABSTRACT

Enzymes are the essential catalytic components of biology and adsorbing redox-active enzymes on electrode surfaces enables the direct probing of their function. Through standard electrochemical measurements, catalytic activity, reversibility and stability, potentials of redox-active cofactors, and interfacial electron transfer rates can be readily measured. Mechanistic investigations on the high electrocatalytic rates and selectivity of enzymes may yield inspiration for the design of synthetic molecular and heterogeneous electrocatalysts. Electrochemical investigations of enzymes also aid in our understanding of their activity within their biological environment and why they evolved in their present structure and function. However, the conventional array of electrochemical techniques (e.g., voltammetry and chronoamperometry) alone offers a limited picture of the enzyme-electrode interface. How many enzymes are loaded onto an electrode? In which orientation(s) are they bound? What fraction is active, and are single or multilayers formed? Does this static picture change over time, applied voltage, or chemical environment? How does charge transfer through various intraprotein cofactors contribute to the overall performance and catalytic bias? What is the distribution of individual enzyme activities within an ensemble of active protein films? These are central questions for the understanding of the enzyme-electrode interface, and a multidisciplinary approach is required to deliver insightful answers. Complementing standard electrochemical experiments with an orthogonal set of techniques has recently allowed to provide a more complete picture of enzyme-electrode systems. Within this framework, we first discuss a brief history of achievements and challenges in enzyme electrochemistry. We subsequently describe how the aforementioned challenges can be overcome by applying advanced electrochemical techniques, quartz-crystal microbalance measurements, and spectroscopic, namely, resonance Raman and infrared, analysis. For example, rotating ring disk electrochemistry permits the simultaneous determination of reaction kinetics and quantification of generated products. In addition, recording changes in frequency and dissipation in a quartz crystal microbalance allows to shed light into enzyme loading, relative orientation, clustering, and denaturation at the electrode surface. Resonance Raman spectroscopy yields information on ligation and redox state of enzyme cofactors, whereas infrared spectroscopy provides insights into active site states and the protein secondary and tertiary structure. The development of these emerging methods for the analysis of the enzyme-electrode interface is the primary focus of this Account. We also take a critical look at the remaining gaps in our understanding and challenges lying ahead toward attaining a complete mechanistic picture of the enzyme-electrode interface.


Subject(s)
Electrochemical Techniques/methods , Enzymes, Immobilized/analysis , Adsorption , Catalytic Domain , Coenzymes/chemistry , Electrochemical Techniques/instrumentation , Electrodes , Enzymes, Immobilized/chemistry , Oxidation-Reduction , Spectrum Analysis
5.
J Am Chem Soc ; 141(44): 17498-17502, 2019 11 06.
Article in English | MEDLINE | ID: mdl-31638793

ABSTRACT

The biological formate hydrogenlyase (FHL) complex links a formate dehydrogenase (FDH) to a hydrogenase (H2ase) and produces H2 and CO2 from formate via mixed-acid fermentation in Escherichia coli. Here, we describe an electrochemical and a colloidal semiartificial FHL system that consists of an FDH and a H2ase immobilized on conductive indium tin oxide (ITO) as an electron relay. These in vitro systems benefit from the efficient wiring of a highly active enzyme pair and allow for the reversible conversion of formate to H2 and CO2 under ambient temperature and pressure. The hybrid systems provide a template for the design of synthetic catalysts and surpass the FHL complex in vivo by storing and releasing H2 on demand by interconverting CO2/H2 and formate with minimal bias in either direction.

6.
Angew Chem Int Ed Engl ; 58(14): 4601-4605, 2019 03 26.
Article in English | MEDLINE | ID: mdl-30724432

ABSTRACT

The integration of enzymes with synthetic materials allows efficient electrocatalysis and production of solar fuels. Here, we couple formate dehydrogenase (FDH) from Desulfovibrio vulgaris Hildenborough (DvH) to metal oxides for catalytic CO2 reduction and report an in-depth study of the resulting enzyme-material interface. Protein film voltammetry (PFV) demonstrates the stable binding of FDH on metal-oxide electrodes and reveals the reversible and selective reduction of CO2 to formate. Quartz crystal microbalance (QCM) and attenuated total reflection infrared (ATR-IR) spectroscopy confirm a high binding affinity for FDH to the TiO2 surface. Adsorption of FDH on dye-sensitized TiO2 allows for visible-light-driven CO2 reduction to formate in the absence of a soluble redox mediator with a turnover frequency (TOF) of 11±1 s-1 . The strong coupling of the enzyme to the semiconductor gives rise to a new benchmark in the selective photoreduction of aqueous CO2 to formate.


Subject(s)
Carbon Dioxide/chemistry , Formate Dehydrogenases/chemistry , Titanium/chemistry , Carbon Dioxide/metabolism , Catalysis , Electrodes , Formate Dehydrogenases/metabolism , Formates/chemistry , Formates/metabolism , Models, Molecular , Molecular Structure , Oxidation-Reduction , Photochemical Processes , Quartz Crystal Microbalance Techniques , Semiconductors , Spectrophotometry, Infrared , Titanium/metabolism
7.
J Am Chem Soc ; 140(48): 16418-16422, 2018 12 05.
Article in English | MEDLINE | ID: mdl-30452863

ABSTRACT

Solar-driven coupling of water oxidation with CO2 reduction sustains life on our planet and is of high priority in contemporary energy research. Here, we report a photoelectrochemical tandem device that performs photocatalytic reduction of CO2 to formate. We employ a semi-artificial design, which wires a W-dependent formate dehydrogenase (FDH) cathode to a photoanode containing the photosynthetic water oxidation enzyme, Photosystem II, via a synthetic dye with complementary light absorption. From a biological perspective, the system achieves a metabolically inaccessible pathway of light-driven CO2 fixation to formate. From a synthetic point of view, it represents a proof-of-principle system utilizing precious-metal-free catalysts for selective CO2-to-formate conversion using water as an electron donor. This hybrid platform demonstrates the translatability and versatility of coupling abiotic and biotic components to create challenging models for solar fuel and chemical synthesis.


Subject(s)
Carbon Dioxide/chemistry , Formate Dehydrogenases/chemistry , Photosystem II Protein Complex/chemistry , Biocatalysis/radiation effects , Coloring Agents/chemistry , Coloring Agents/radiation effects , Cyanobacteria/enzymology , Desulfovibrio vulgaris/enzymology , Electrochemical Techniques/instrumentation , Electrochemical Techniques/methods , Electrodes , Ketones/chemistry , Ketones/radiation effects , Light , Oxidation-Reduction , Photosystem II Protein Complex/radiation effects , Plastoquinone/chemistry , Proof of Concept Study , Pyrroles/chemistry , Pyrroles/radiation effects , Titanium/chemistry , Water/chemistry
8.
Environ Sci Technol ; 52(16): 9419-9430, 2018 08 21.
Article in English | MEDLINE | ID: mdl-29953215

ABSTRACT

Transcriptomics, high-throughput assays, and adverse outcome pathways (AOP) are promising approaches applied to toxicity monitoring in the 21st century, but development of these methods is challenging for nonmodel organisms and emerging contaminants. For example, Endocrine Disrupting Compounds (EDCs) may cause reproductive impairments and feminization of male bivalves; however, the mechanism linked to this adverse outcome is unknown. To develop mechanism-based biomarkers that may be linked through an AOP, we exposed Mytilus edulis to 17-alpha-ethinylestradiol (5 and 50 ng/L) and 4-nonylphenol (1 and 100 µg/L) for 32 and 39 days. When mussels were exposed to these EDCs, we found elevated female specific transcripts and significant female-skewed sex ratios using a RT-qPCR assay. We performed gene expression analysis on digestive gland tissue using an M. edulis microarray and through network and targeted analyses identified the nongenomic estrogen signaling pathway and steroidogenesis pathway as the likely mechanisms of action for a putative AOP. We also identified several homologues to genes within the vertebrate steroidogenesis pathway including the cholesterol side chain cleavage complex. From this AOP, we designed the Coastal Biosensor for Endocrine Disruption (C-BED) assay which was confirmed in the laboratory and tested in the field.


Subject(s)
Endocrine Disruptors , Mytilus edulis , Mytilus , Water Pollutants, Chemical , Animals , Biomarkers , Endocrine System , Female , Male , Transcriptome
9.
J Am Chem Soc ; 139(29): 9927-9936, 2017 07 26.
Article in English | MEDLINE | ID: mdl-28635274

ABSTRACT

Molybdenum-containing formate dehydrogenase H from Escherichia coli (EcFDH-H) is a powerful model system for studies of the reversible reduction of CO2 to formate. However, the mechanism of FDH catalysis is currently under debate, and whether the primary Mo coordination sphere remains saturated or one of the ligands dissociates to allow direct substrate binding during turnover is disputed. Herein, we describe how oxidation-state-dependent changes at the active site alter its inhibitor binding properties. Using protein film electrochemistry, we show that formate oxidation by EcFDH-H is inhibited strongly and competitively by N3-, OCN-, SCN-, NO2-, and NO3-, whereas CO2 reduction is inhibited only weakly and not competitively. During catalysis, the Mo center cycles between the formal Mo(VI)═S and Mo(IV)-SH states, and by modeling chronoamperometry data recorded at different potentials and substrate and inhibitor concentrations, we demonstrate that both formate oxidation and CO2 reduction are inhibited by selective inhibitor binding to the Mo(VI)═S state. The strong dependence of inhibitor-binding affinity on both Mo oxidation state and inhibitor electron-donor strength indicates that inhibitors (and substrates) bind directly to the Mo center. We propose that inhibitors bind to the Mo following dissociation of a selenocysteine ligand to create a vacant coordination site for catalysis and close by considering the implications of our data for the mechanisms of formate oxidation and CO2 reduction.


Subject(s)
Carbon Dioxide/metabolism , Coordination Complexes/chemistry , Escherichia coli/enzymology , Formate Dehydrogenases/chemistry , Formates/metabolism , Molybdenum/chemistry , Binding Sites , Carbon Dioxide/chemistry , Catalytic Domain , Coordination Complexes/metabolism , Formate Dehydrogenases/metabolism , Formates/chemistry , Molybdenum/metabolism , Oxidation-Reduction
10.
Bioorg Chem ; 71: 219-229, 2017 04.
Article in English | MEDLINE | ID: mdl-28228229

ABSTRACT

Tunichromes, small oligopeptides with dehydrodopa units isolated from the blood cells of ascidians, have been implicated in the defense reactions, metal binding, wound repair, or tunic formation. Their instability and high reactivity has severely hampered the assessment of their biological role. Experiments conducted with the model compound, 1,2-dehydro-N-acetyldopamine, indicated that the instability of tunichromes is due to this basic structure. Exposure of this catecholamine derivative to even mild alkaline condition such as pH 7.5 causes rapid nonenzymatic oxidation. High performance liquid chromatography and mass spectrometry studies confirmed the production of dimeric and other oligomeric products in the reaction mixture. The nonenzymatic reaction seemed to proceed through the intermediary formation of semiquinone free radical and superoxide anion. Ultraviolet and visible spectral studies associated with the oxidation of tunichromes isolated from Ascidia nigra by tyrosinase indicated the probable formation of oligomeric tunichrome products. Attempts to monitor the polymerization reaction by mass spectrometry ended in vain. Tunichrome also exhibited instability in mild alkaline conditions generating superoxide anions. Based on these studies, a possible role for oxidative transformation of tunichrome in defense reaction, tunic formation and wound healing is proposed.


Subject(s)
Dopamine/analogs & derivatives , Organic Chemicals/chemistry , Urochordata/chemistry , Agaricales/enzymology , Animals , Chromatography, High Pressure Liquid , Coordination Complexes/chemistry , Dopamine/chemistry , Dopamine/metabolism , Free Radicals/chemistry , Hydrogen-Ion Concentration , Mass Spectrometry , Monophenol Monooxygenase/metabolism , Oligopeptides/chemistry , Oligopeptides/metabolism , Organic Chemicals/metabolism , Oxidation-Reduction
11.
Nat Chem ; 14(6): 623-631, 2022 06.
Article in English | MEDLINE | ID: mdl-35668214

ABSTRACT

The evolution of life from the prebiotic environment required a gradual process of chemical evolution towards greater molecular complexity. Elaborate prebiotically relevant synthetic routes to the building blocks of life have been established. However, it is still unclear how functional chemical systems evolved with direction using only the interaction between inherent molecular chemical reactivity and the abiotic environment. Here we demonstrate how complex systems of chemical reactions exhibit well-defined self-organization in response to varying environmental conditions. This self-organization allows the compositional complexity of the reaction products to be controlled as a function of factors such as feedstock and catalyst availability. We observe how Breslow's cycle contributes to the reaction composition by feeding C2 building blocks into the network, alongside reaction pathways dominated by formaldehyde-driven chain growth. The emergence of organized systems of chemical reactions in response to changes in the environment offers a potential mechanism for a chemical evolution process that bridges the gap between prebiotic chemical building blocks and the origin of life.


Subject(s)
Origin of Life , Prebiotics , Catalysis , Chemical Phenomena , Evolution, Chemical
12.
Article in English | MEDLINE | ID: mdl-34952324

ABSTRACT

Mollusks, especially bivalves, exhibit a great diversity of sex determining mechanisms, including both genetic and environmental sex determination. Some bivalve species can be gonochoristic (separate sexes), while others are hermaphroditic (sequential or simultaneous). Several models have been proposed for specific bivalve species, utilizing information gained from gene expression data, as well as limited RAD-seq data (e.g., from Crassostrea gigas). However, these mechanisms are not as well studied as those in model organisms (e.g., Mus musculus, Drosophila melanogaster, Caenorhabditis elegans) and many genes involved in sex differentiation are not well characterized. We used phylotranscriptomics to better understand which possible sex differentiating genes are in bivalves and how these genes relate to similar genes in diverse phyla. We collected RNAseq data from eight phylogenetically diverse bivalve species: Argopecten irradians, Ensis directus, Geukensia demissa, Macoma tenta, Mercenaria mercenaria, Mya arenaria, Mytilus edulis, and Solemya velum. Using these data, we assembled representative transcriptomes for each species. We then searched for candidate sex differentiating genes using BLAST and confirmed the identity of nine genes using phylogenetics analyses from nine phyla. To increase the confidence of identification, we included ten bivalve genomes in our analyses. From the analysis of doublesex and mab-3 related transcription factor (DMRT) genes, we confirmed the identify of a Mollusk-specific sex determining DMRT gene: DMRT1L. Based on gene expression data from M. edulis and previous research, DMRT1L and FoxL2 are key genes for male and female development, respectively.


Subject(s)
Crassostrea , Pectinidae , Animals , Crassostrea/genetics , Drosophila melanogaster , Female , Male , Mice , Pectinidae/genetics , Phylogeny , Sex Differentiation/genetics
13.
Mar Drugs ; 8(12): 2906-35, 2010 Dec 06.
Article in English | MEDLINE | ID: mdl-21339956

ABSTRACT

The amino acid, tyrosine, and its hydroxylated product, 3,4-dihydroxyphenylalanine (dopa), plays an important role in the biogenesis of a number of potentially important bioactive molecules in marine organisms. Interestingly, several of these tyrosyl and dopa-containing compounds possess dehydro groups in their side chains. Examples span the range from simple dehydrotyrosine and dehydrodopamines to complex metabolic products, including peptides and polycyclic alkaloids. Based on structural information, these compounds can be subdivided into five categories: (a) Simple dehydrotyrosine and dehydrotyramine containing molecules; (b) simple dehydrodopa derivatives; (c) peptidyl dehydrotyrosine and dehydrodopa derivatives; (d) multiple dehydrodopa containing compounds; and (e) polycyclic condensed dehydrodopa derivatives. These molecules possess a wide range of biological activities that include (but are not limited to) antitumor activity, antibiotic activity, cytotoxicity, antioxidant activity, multidrug resistance reversal, cell division inhibition, immunomodulatory activity, HIV-integrase inhibition, anti-viral, and anti-feeding (or feeding deterrent) activity. This review summarizes the structure, distribution, possible biosynthetic origin, and biological activity, of the five categories of dehydrotyrosine and dehydrodopa containing compounds.


Subject(s)
Anti-Bacterial Agents/therapeutic use , Antineoplastic Agents/therapeutic use , Aquatic Organisms/chemistry , Biological Products/therapeutic use , Dihydroxyphenylalanine/analogs & derivatives , Invertebrates/chemistry , Tyrosine/analogs & derivatives , Animals , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/isolation & purification , Antineoplastic Agents/chemistry , Antineoplastic Agents/isolation & purification , Biological Products/chemistry , Biological Products/isolation & purification , Dihydroxyphenylalanine/chemistry , Peptides/chemistry , Peptides/therapeutic use , Polycyclic Compounds/chemistry , Polycyclic Compounds/therapeutic use , Tyrosine/chemistry
14.
Aquat Toxicol ; 220: 105397, 2020 Mar.
Article in English | MEDLINE | ID: mdl-31954981

ABSTRACT

Within monitoring frameworks, biomarkers provide several benefits because they serve as intermediates between pollutant exposure and effects, and integrate the responses of contaminants that operate through the same mechanism of action. This study was designed to verify the use of transcriptomic biomarkers developed in our prior work (i.e., Coastal Biosensor of Endocrine Disruption; C-BED assay) on Mytilus edulis and identify additional biomarkers for legacy pollutants. M. edulis were collected from a reference site in Pemaquid, ME, USA and deployed by the Massachusetts Water Resources Authority (MWRA) at locations in and outside Boston Harbor, MA, USA: including (1) Boston Inner Harbor (IH), (2) the current outfall (OS), (3) 1 km away from the current outfall (LNB), and (4) Deer Island (DI), the site where untreated wastewater was formerly discharged into the bay. Differential gene expression was quantified with a high density microarray. Seven genes significantly correlated with whole tissue concentration of PAHs, and six genes significantly correlated with whole body concentrations of PCBs, two groups of legacy contaminants that were elevated at stations IH, OS, and DI. Enrichment analysis indicated that IH mussels had the highest induction of stress response genes, which correlated with the higher levels of contaminants measured at this site. Based on the C-BED assay gene analysis, stations IH and OS exhibited signs of endocrine disruption, which were further confirmed by incorporating the results for the C-BED assay within the Integrated Biomarker Response (IBR) approach. This study successfully demonstrated the potential use of transcriptomic biomarkers within a monitoring program to identify the presence and organismal responses to endocrine disrupting and legacy contaminant classes.


Subject(s)
Endocrine Disruptors/toxicity , Environmental Biomarkers/genetics , Environmental Monitoring/methods , Mytilus edulis/drug effects , Transcriptome/drug effects , Water Pollutants, Chemical/toxicity , Animals , Endocrine Disruptors/analysis , Mytilus edulis/genetics , New England , Polychlorinated Biphenyls/analysis , Polychlorinated Biphenyls/toxicity , Polycyclic Aromatic Hydrocarbons/analysis , Polycyclic Aromatic Hydrocarbons/toxicity , Seawater/chemistry , Water Pollutants, Chemical/analysis
15.
Article in English | MEDLINE | ID: mdl-18593604

ABSTRACT

Tunichromes are small peptides containing one or more dehydrodopa derived units that have been identified in the blood cells of at least eleven species of tunicates. Incubation of tunichromes isolated from Ascidia nigra hemocytes (or model dopa-containing compounds) under oxidative conditions with either lysozyme, cytochrome c or ovalbumin resulted in a time-dependent polymerization of these test proteins to dimers, trimers, tetramers and potentially to other oligomers. These results indicate that the oxidation products of tunichromes possess inherent crosslinking properties. Hence it is possible that tunichromes participate in tunic production by forming adducts and crosslinks with structural proteins and/or carbohydrate polymers, similar to the well-understood process of insect cuticle hardening. Since such crosslinking potentials could also be beneficial for defense reactions against invading microorganisms, antibacterial activity of tunichromes was tested using both a radial diffusion assay and the Microtox(R) test. Tunichromes exhibited antimicrobial activity against gram-negative bacteria Escherichia coli and Photobacterium phosphorium. However, they did not show any antimicrobial activity against the gram-positive bacteria Staphylococcus aureus at the concentrations tested. We propose that the crosslinking and antimicrobial functions are both based on the reactivity of dehydrodopa units present in the tunichromes, and their subsequent ability to form highly reactive quinone methides.


Subject(s)
Anti-Infective Agents/metabolism , Anti-Infective Agents/pharmacology , Cross-Linking Reagents/metabolism , Cross-Linking Reagents/pharmacology , Organic Chemicals/metabolism , Organic Chemicals/pharmacology , Animals , Anti-Infective Agents/chemistry , Anti-Infective Agents/isolation & purification , Bacteria/drug effects , Cross-Linking Reagents/chemistry , Cross-Linking Reagents/isolation & purification , Diffusion , Dopamine/analogs & derivatives , Dopamine/metabolism , Dopamine/pharmacology , Organic Chemicals/chemistry , Organic Chemicals/isolation & purification , Polymers/metabolism , Proteins/metabolism , Urochordata/chemistry
16.
Article in English | MEDLINE | ID: mdl-18567521

ABSTRACT

Four tissues from the blue mussel, Mytilus edulis L., were examined for the presence of nuclear metallothionein (MT), and the nuclear:cytosolic (N:C) MT ratios and nuclear MT:DNA ratios investigated. Gill, digestive gland, gonad and posterior adductor muscle tissues were dissected, homogenized and subjected to differential centrifugation in order to isolate the nuclear and cytosolic fractions, which were then analyzed for MT and DNA. MT was present in all samples of the nuclear fractions from all four tissues. The nuclear MT concentration was either lower or the same as the cytosolic MT concentration from the same tissue. The mean N:C MT ratio of the digestive gland was significantly lower than that of the gill. The mean nuclear MT:DNA ratio of the digestive gland was significantly higher than that of the gill and posterior adductor muscle. In addition to being the first report of nuclear MT in bivalves, we showed that N:C MT ratios and nuclear MT:DNA ratios differ among tissues of the same organism. This raises important questions concerning the regulation of nuclear MT concentrations and the role of nuclear MT in metal regulation and DNA protection.


Subject(s)
Cell Nucleus/metabolism , Cytosol/metabolism , Metallothionein/metabolism , Mytilus edulis/cytology , Mytilus edulis/metabolism , Animals , Cytoplasm/metabolism , DNA/metabolism , Ecosystem , Environmental Monitoring
17.
Article in English | MEDLINE | ID: mdl-17276716

ABSTRACT

Histidine-rich Glycoprotein (HRG) is a metal-binding protein described from the blood plasma of a pteriomorph bivalve, the marine mussel Mytilus edulis L. We demonstrate here, using Cd-Immobilized Metal Affinity Chromatography (IMAC), SDS-PAGE, Western Blotting, and ELISA, that HRG is present in three additional pteriomorphs and two heterodont bivalves. ELISA indicates that HRG is the predominant blood plasma protein in all six species (41 to 61% of total plasma proteins by weight). Thus, HRG appears to be a widespread metal-binding protein in the plasma of bivalves.


Subject(s)
Bivalvia/chemistry , Proteins/analysis , Animals , Blotting, Western , Chromatography, Affinity , Chromatography, Ion Exchange , Electrophoresis, Polyacrylamide Gel , Enzyme-Linked Immunosorbent Assay , Molecular Weight
18.
Environ Toxicol Chem ; 26(5): 872-7, 2007 May.
Article in English | MEDLINE | ID: mdl-17521131

ABSTRACT

Few studies have directly addressed the question of how metals (both essential and nonessential) are transported in the circulatory system of bivalve mollusks. One potential metal-transport protein, histidine-rich glycoprotein (HRG), has previously been isolated and characterized from the blood plasma of the marine mussel Mytilus edulis L. The present study was undertaken to investigate the extent to which mussel HRG can bind a variety of essential and nonessential metals in vitro, using immobilized metal-ion affinity chromatography (IMAC) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The equilibrium metal speciation model MINTEQA2 was used to compute the amount of metal that bound to the IMAC packing material during the charging and initial wash steps. Results demonstrated that HRG can bind all seven of the metals tested (Ca, Cd, Hg, Mg, Ni, Pd, and Zn) and that HRG is the only metal-binding protein in IMAC eluents. Because HRG-metal binding strengths (log K(a)) likely correspond with histidine-metal binding strengths, and because HRG is the predominant mussel plasma protein, the majority of each of the seven metals probably would be present in mussel blood as protein-bound metal rather than as free metal ion. The finding that a single mussel plasma protein may be responsible for binding all these metals raises important questions about how these different metals are subsequently transferred from HRG to different tissues of the mussel, where they may exhibit tissue-specific patterns of utilization, sequestration, elimination, and toxicity.


Subject(s)
Hemolymph/metabolism , Metals/metabolism , Mytilus edulis/metabolism , Proteins/metabolism , Animals , Binding Sites , Cations , Chromatography, Affinity , Electrophoresis, Polyacrylamide Gel
19.
Environ Toxicol Chem ; 35(4): 863-73, 2016 Apr.
Article in English | MEDLINE | ID: mdl-26126666

ABSTRACT

Endocrine-disrupting compounds (EDCs), including 17α-ethinyl estradiol (EE2) and 4-nonylphenol (4-NP), enter coastal environments primarily in effluents of wastewater treatment facilities and have become ubiquitous in marine surface waters, sediments, and biota. Although EE2 and 4-NP have been detected in marine shellfish, the kinetics of bioconcentration and their tissue distribution have not been thoroughly investigated. The authors performed bioconcentration and depuration experiments in the blue mussel, Mytilus edulis, with 3.37 nM EE2 (0.999 µg/L) and 454 nM 4-NP (100.138 µg/L). Mussels and seawater were sampled throughout a 38-d exposure and a 35-d depuration period, and 6 tissues were individually assayed. Uptake of EE2 and 4-NP was curvilinear throughout exposure and followed a similar uptake pattern: digestive gland > gill ≥ remaining viscera > gonad > adductor > plasma. Depuration varied, however, with half-lives ranging from 2.7 d (plasma) to 92 d (gill) for EE2 and 15 d (plasma) to 57 d (gill) for 4-NP. An innovative modeling approach, with 3 coupled mathematical models, was developed to differentiate the unique roles of the gill and plasma in distributing the EDCs to internal tissues. Plasma appears pivotal in regulating EDC uptake and depuration within the whole mussel.


Subject(s)
Aquatic Organisms/metabolism , Environmental Monitoring/methods , Ethinyl Estradiol/metabolism , Mytilus edulis/metabolism , Organ Specificity , Phenols/metabolism , Animals , Carbon Radioisotopes , Half-Life , Kinetics , Seawater/chemistry , Tissue Distribution
20.
Environ Toxicol Chem ; 24(9): 2341-9, 2005 Sep.
Article in English | MEDLINE | ID: mdl-16193764

ABSTRACT

A diverse laboratory population of Daphnia magna Straus was established by combining individuals from eight sources. Artificial selection for increased resistance to the acute toxic effects of cadmium was performed, and after eight generations, the average median effective concentration increased from 61 to 180 microg/L. No differences in life span, offspring production, time to first brood, number of offspring in the first brood, or intrinsic rate of population increase (r) were observed between the cadmium-adapted population and the controls under ideal conditions or under conditions of temperature or feeding ration stress, but cadmium-adapted daphnids were smaller. Control and cadmium-adapted populations were equally sensitive to copper and malathion, but the cadmium-adapted population was less sensitive to lead and more sensitive to phenol. Analysis of amplified fragment-length polymorphisms indicated a significant decrease in genetic diversity in the cadmium-adapted population. Although the evolved cadmium resistance would allow adapted populations to exist in areas where cadmium concentrations would be toxic to unadapted populations, the decreased genetic diversity, smaller size, and increased sensitivity to at least one other toxicant could reduce the probability of long-term survival even in the absence of future cadmium exposure.


Subject(s)
Cadmium Poisoning , Cadmium/pharmacology , Cadmium/toxicity , Drug Resistance , Environmental Monitoring/methods , Adaptation, Physiological , Animals , Cadmium/chemistry , Daphnia , Dose-Response Relationship, Drug , Ecology , Genetic Variation , Life Cycle Stages/drug effects , Models, Statistical , Polymorphism, Genetic , Reproduction/drug effects , Temperature , Toxicity Tests/methods , Water Pollutants, Chemical
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