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1.
Adv Exp Med Biol ; 1131: 163-182, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31646510

RESUMO

Calcium (Ca2+) buffering is part of an integrative crosstalk between different mechanisms and elements involved in the control of free Ca2+ ions persistence in the cytoplasm and hence, in the Ca2+-dependence of many intracellular processes. Alterations of Ca2+ homeostasis and signaling from systemic to subcellular levels also play a pivotal role in the pathogenesis of many diseases.Compared with Ca2+ sequestration towards intracellular Ca2+ stores, Ca2+ buffering is a rapid process occurring in a subsecond scale. Any molecule (or binding site) with the ability to bind Ca2+ ions could be considered, at least in principle, as a buffer. However, the term Ca2+ buffer is applied only to a small subset of Ca2+ binding proteins containing acidic side-chain residues.Ca2+ buffering in the cytoplasm mainly relies on mobile and immobile or fixed buffers controlling the diffusion of free Ca2+ ions inside the cytosol both temporally and spatially. Mobility of buffers depends on their molecular weight, but other parameters as their concentration, affinity for Ca2+ or Ca2+ binding and dissociation kinetics next to their diffusional mobility also contribute to make Ca2+ signaling one of the most complex signaling activities of the cell.The crosstalk between all the elements involved in the intracellular Ca2+ dynamics is a process of extreme complexity due to the diversity of structural and molecular elements involved but permit a highly regulated spatiotemporal control of the signal mediated by Ca2+ ions. The basis of modeling tools to study Ca2+ dynamics are also presented.


Assuntos
Sinalização do Cálcio , Cálcio , Citoplasma , Animais , Tampões (Química) , Cálcio/metabolismo , Sinalização do Cálcio/fisiologia , Citoplasma/metabolismo , Humanos
2.
J Environ Qual ; 48(4): 915-921, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31589696

RESUMO

Measurement of the retention of dissolved nutrients in riparian areas with snowmelt runoff are much less common than for rainfall runoff, but low rates of uptake or the release of nutrients with snowmelt have been attributed to frozen soils, lower biotic uptake, and release of nutrients from senesced vegetation. In the research presented here, we evaluate whether the potential for uptake of dissolved reactive phosphorus (DRP) and NO differ significantly between snowmelt and summer seasons with flow through 13 riparian buffers downstream of cropland in Manitoba, Canada. Flow-through buffers in small channels are typical in this landscape, and pulsed releases of a conservative tracer and dissolved nutrients were used to measure uptake rates. Although mean uptake rates of NO were higher in summer than for snowmelt, responses varied widely. Aerial uptake rate of DRP showed a significant negative relationships with soil Olsen-P ( = 0.54, < 0.001) and a P saturation index ( = 0.48, < 0.001) across both seasons. Biological processes may be of greater importance for NO retention, but DRP retention appears to be driven by adsorption-desorption regardless of season. Olsen-P is identified as a good indicator of potential for release or retention of DRP in riparian buffers with fine-textured calcareous soils, for both snowmelt and summer seasons. Soil testing may be a good tool to aid in the siting of new buffers and to track the effectiveness of management interventions to remove P from riparian areas, such as harvest of vegetation.


Assuntos
Fósforo , Solo , Tampões (Química) , Canadá , Nitratos
3.
Compend Contin Educ Dent ; 40(7): e1-e10, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31478693

RESUMO

BACKGROUND: Alkalinization or buffering of dental local anesthetics to raise the pH of these acidic solutions is a well-documented technique that results in clinical benefits such as decreased injection pain, reduced onset time, and the need for less overall volume of local anesthesia. OBJECTIVE: In a previous study, two options available for buffering local anesthetics in dentistry were compared, one using the Onpharma® mixing system (Onpharma), and the other by hand mixing with 8.4% sodium bicarbonate using a "remove and replace" technique. The results of that study showed no statistically significant difference in buffering outcomes between the two methods. This follow-up in vitro study introduces and examines a less complex, direct injection, chairside hand-mixing approach using four commercially available dental local anesthetic preparations. MATERIALS AND METHODS: The authors prepared multiple buffered samples of four different commercially available local anesthetic solutions. The buffered samples were mixed to 9:1, 19:1, and 18:1 ratios (local anesthetic to 8.4% sodium bicarbonate). Sample pH was recorded using a pH meter. Two samples of each local anesthetic at each ratio were prepared and sequentially pH tested. The pH was recorded via the same pH meter, which was cleaned between each test. RESULTS: The pH change between unbuffered solutions and all buffered samples was statistically different (P < .01, CI 99%). There was no final pH difference between the 9:1 and 19:1, and 19:1 and 18:1 buffering ratios (P > .01); however, a statistical difference was seen between the final pHs of the solutions resulting from the 9:1 and 18:1 buffering ratios (P = .006, CI 99%). After correction for multiple comparisons, the difference between the 9:1 and 18:1 ratio was marginally significant (P = .048). CONCLUSIONS: Each of the buffering ratios tested can be used to alkalinize dental local anesthetic solutions. For practical purposes, a direct injection chairside of 0.1 mL of 8.4% sodium bicarbonate into any of the four local anesthetics tested is easy, simple, and safe compared to the more complex remove and replace method. Further studies are needed to evaluate if a clinically significant difference exists between the 9:1, 19:1, and 18:1 ratio solutions. CLINICAL IMPLICATIONS: The potential benefits of buffering local anesthetic solutions prior to injection, such as decreased injection pain, faster onset, and greater depth of anesthesia, may be particularly advantageous in patients who have difficulty achieving profound anesthesia for clinical dentistry, and for anesthetizing infected areas. Dentists can effectively buffer local anesthetic preparations using commercially available mixing systems or by utilizing a hand-mixing technique. Rather than using a remove and replace technique, practitioners may consider a direct injection technique, adding 0.1 mL of 8.4% sodium bicarbonate directly into any local anesthetic cartridge regardless of local anesthetic concentration.


Assuntos
Anestesia Local , Anestésicos Locais , Tampões (Química) , Método Duplo-Cego , Humanos , Concentração de Íons de Hidrogênio , Lidocaína , Bicarbonato de Sódio
4.
Pharm Res ; 36(11): 152, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31463609

RESUMO

PURPOSE: To develop an analytical platform for the estimation as well as characterization of aggregates over the complete size spectrum (from invisible monomer to visible precipitates). METHODS: Two mAb samples were incubated at 30°C in different buffer systems of protein A chromatography for observing degradation due to aggregation. The aggregation in these samples was quantified by size exclusion chromatography (SEC), dynamic light scattering (DLS), and micro flow imaging (MFI). RESULTS: The results obtained from various characterization tools were analysed in various size ranges - size exclusion chromatography (SEC) (1 nm - 25 nm), dynamic light scattering (DLS) (10 nm - 5 µm), and micro flow imaging (MFI) (2 µm - 300 µm). Since each characterization tool covers a particular size range, data from multiple tools was collected in the "handover" regions to demonstrate accuracy of the platform. CONCLUSIONS: Based on the observations from the experiments, an analytical platform has been proposed covering the whole size spectrum that would be of utility to those engaged in formulation development as well as other aspects related to stability of biotherapeutic products.


Assuntos
Anticorpos Monoclonais/análise , Tampões (Química) , Cromatografia em Gel , Cromatografia Líquida de Alta Pressão , Difusão Dinâmica da Luz , Nanopartículas/química , Tamanho da Partícula , Multimerização Proteica , Estabilidade Proteica
5.
J Chromatogr A ; 1602: 397-408, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31285058

RESUMO

In reversed-phase liquid chromatography, the performance for basic compounds is affected by the interaction of the protonated (cationic) species with the anionic free silanols on the alkyl-bonded stationary phases. Using aqueous-organic mobile phases in the absence of additives, the retention may be too high, and the peaks be broad and asymmetric. The performance is improved by addition to the mobile phase of ionic liquids, from which 1-hexyl-3-methylimidazolium chloride ([C6MIm][Cl]) has especially good characteristics. A recent report has also revealed that the use of the phosphate system as buffer, at varying concentration and pH, may have a significant role in the chromatographic performance of basic compounds, with effects on both retention and peak shape. In this work, this study has been extended to other three buffer systems (acetate, citrate, and formate), at increasing concentrations and pH 3 and 7, in the presence and absence of [C6MIm][Cl]. The results have been compared with those obtained with the phosphate system. The retention increases by addition of larger concentration of all buffers, in both absence and presence of [C6MIm][Cl]. Without additive, peak performance is also enhanced significantly. This effect is minimal in the presence of [C6MIm][Cl], which yields highly symmetrical peaks at all buffer concentrations, due to an effective blocking of the silanol activity.


Assuntos
Boratos/química , Cromatografia de Fase Reversa/métodos , Imidazóis/química , Acetonitrilos/química , Antagonistas Adrenérgicos beta/análise , Tampões (Química) , Cromatografia Líquida de Alta Pressão/métodos , Concentração de Íons de Hidrogênio , Líquidos Iônicos/química , Solventes , Água/química
6.
Waste Manag ; 95: 356-364, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-31351621

RESUMO

Odour is a significant challenge for regulators of waste handling facilities due to the increasing demand for land surrounding these facilities. Many sites, including landfills, composters, abattoirs and rendering plants, that were once isolated are now close to residential areas. In some cases, this has contributed to odour impacts on residents living in those areas. Authorities have been reliant on odour modelling and odour design criteria to predict or estimate the distance at which impacts are likely to occur on sensitive land use. However, it is increasingly evident that reliance on modelling tools, and the estimated odour emission rates used in modelling, are not reflecting ground level observations. Environment Protection Authority Victoria ("EPA") conducted six in-field odour monitoring campaigns between 2007 and 2017. We studied these six campaigns to understand the extent of odour plumes from waste handling facilities. The campaigns used odour surveillance methodology developed by EPA. They consisted of in-field odour assessments around common waste handling facilities such as composters, landfills, abattoirs and rendering plants. We used the results of surveillance in conjunction with reverse trajectory plotting to estimate the typical extent and frequency of odour plumes as a function of distance. The study showed that the application of consistent in-field odour assessment methodologies improved understanding of odour plumes, and hence increases the options available to manage impacts.


Assuntos
Odorantes , Instalações de Eliminação de Resíduos , Tampões (Química) , Conservação dos Recursos Naturais , Monitoramento Ambiental
7.
J Chromatogr A ; 1603: 113-129, 2019 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-31262515

RESUMO

A protocol was defined which utilised peptides as probes for the characterisation of reversed phase chromatography peptide separation systems. These peptide probes successfully distinguished between differing stationary phases through the probe's hydrophobic, electrostatic, hydrogen bonding and aromatic interactions with the stationary phase, in addition, to more subtle interactions such as the phase's ability to separate racemic or isomeric probes. The dominating forces responsible for the chromatographic selectivity of peptides appear to be hydrophobic as well as electrostatic and polar in nature. This highlights the need for other types of stationary phase ligands with possibly mixed mode functionalities / electrostatic / polar interactions for peptide separations rather than the hydrophobic ligands which dominate small molecule separations. Selectivity differences are observed between phases, but it appears that it is the accessibility differences between these phases which play a crucial role in peptide separations i.e. accessibility to silanols, the hydrophobic acetonitrile / ligand layer or a thin adsorbed water layer on the silica surface.


Assuntos
Cromatografia de Fase Reversa/métodos , Peptídeos/isolamento & purificação , Sequência de Aminoácidos , Tampões (Química) , Ligações de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Peptídeos/química , Análise de Componente Principal , Eletricidade Estática
8.
J Chromatogr A ; 1602: 341-349, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31204039

RESUMO

Protein purification by affinity chromatography relies primarily on the interaction of a fused-tag to the protein of interest. Here, we describe a tag-free affinity method that employs functional selection interactions to a broad range of proteins. To achieve this, we coupled human DNA-clamp proliferating cell nuclear antigen (PCNA) that interacts with over one hundred proteins to an agarose resin. We demonstrate the versatility of our PCNA-Agarose column at various chromatographic steps by purifying PCNA-binding proteins that are involved in DNA Replication (DNA polymerase δ, flap endonuclease 1 and DNA ligase 1), translesion DNA synthesis (DNA polymerases eta, kappa and iota) and genome stability (p15). We also show the competence of the PCNA-Agarose column to purify non-PCNA binding proteins by fusing the PCNA-binding motif of human p21 as an affinity tag. Finally, we establish that our PCNA-Agarose column is a suitable analytical method for characterizing the binding strength of PCNA-binding proteins. The conservation and homology of PCNA-like clamps will allow for the immediate extension of our method to other species.


Assuntos
Cromatografia de Afinidade/métodos , Antígeno Nuclear de Célula em Proliferação/isolamento & purificação , Sefarose/química , Tampões (Química) , DNA Polimerase III/isolamento & purificação , Reparo do DNA , Replicação do DNA , Humanos , Ligação Proteica , Proteínas Recombinantes/isolamento & purificação , Resinas Sintéticas/química
9.
J Chromatogr A ; 1602: 91-99, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31229248

RESUMO

Endotoxins are found almost everywhere and possess high toxicity in vivo and in vitro. Here we design a novel boronate affinity material, called boronic acid-functionalized mesoporous silica-coated core/shell magnetic microspheres (Fe3O4@nSiO2@mSiO2-BA) with large pores (pore size > 20 nm) based on the chemical structure and physical properties of endotoxins, for facile and highly efficient removal of endotoxins. Dual modes for endotoxin removal were proposed and confirmed in this work: the endotoxin aggregates with size < 20 nm were bound with boronic acid ligands chemically modified on the inner and outer surface of the large pores of Fe3O4@nSiO2@mSiO2-BA microspheres; while the larger endotoxin micelles (size >20 nm) were absorbed on the outer surface of the prepared material based on boronate affinity. Transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption/desorption isotherms and Fourier transform infrared (FT-IR) spectroscopy confirm that Fe3O4@nSiO2@mSiO2-BA microspheres possess core/shell structure, uniform diameter (520 nm), high surface area (205.57 m2/g), large mesopores (21.8 nm) and boronic acid ligands. The purification procedures of Fe3O4@nSiO2@mSiO2-BA microspheres for endotoxin were optimized, and 50 mM NH4HCO3 (pH 8.0) and 0.05 M fructose were selected as loading/washing, elution buffers, respectively. The binding capacity of Fe3O4@nSiO2@mSiO2-BA microspheres for endotoxin was calculated to be 60.84 EU/g under the optimized conditions. Finally, the established analytical method was applied to remove endotoxins from plasmid DNA. After endotoxin removal, the endotoxin content in plasmid DNA was reduced from 0.0026 to 0.0006 EU/mL for two-fold concentration, and from 0.0088 to 0.0022 EU/mL for five-fold concentration after binding, respectively. Additional advantages of the prepared boronate affinity material include excellent stability, reusability/repeatability, and low cost. Boronate affinity materials with large pores could thus prove to be powerful adsorbents for endotoxin removal and the potential applications in the aspects of biological research, pharmaceutical industry, and life health.


Assuntos
Ácidos Borônicos/química , Endotoxinas/isolamento & purificação , Magnetismo , Microesferas , Dióxido de Silício/química , Adsorção , Tampões (Química) , Compostos Férricos/química , Porosidade , Padrões de Referência , Difração de Raios X
10.
Mar Pollut Bull ; 142: 129-134, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31232285

RESUMO

Standardized methods for the digestion of biota for microplastic analysis are currently lacking. Chemical methods can be effective, but can also cause damage to some polymers. Enzymatic methods are known to be gentler, but often laborious, expensive and time consuming. A novel tissue digestion method with pancreatic enzymes and a pH buffer (Tris) is here presented in a comparison to a commonly applied digestion protocol with potassium hydroxide. The novel protocol demonstrates a highly efficient removal of bivalve tissue (97.7 ±â€¯0.2% dry weight loss) already over-night. Furthermore, it induces no impairment in terms of ability to correctly identify four pre-weathered plastic polymers and six textile fiber polymers by Fourier transform infrared spectroscopy after exposure. The high-throughput protocol requires minimal handling, is of low cost and does not pose risk to the performer or the environment. It is therefore suggested as a candidate for a standardized digestion protocol, enabling successful analysis of microplastics ingested by bivalves.


Assuntos
Bivalves/química , Ecotoxicologia/métodos , Plásticos/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Animais , Tampões (Química) , Monitoramento Ambiental/métodos , Enzimas/química , Concentração de Íons de Hidrogênio , Hidróxidos/química , Plásticos/análise , Compostos de Potássio/química , Espectroscopia de Infravermelho com Transformada de Fourier , Têxteis/análise , Poluentes Químicos da Água/análise
11.
J Chromatogr A ; 1603: 417-421, 2019 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-31196587

RESUMO

Deamidation of asparagine (Asn) residues of monoclonal antibodies (mAbs) plays a pivotal role in the in vivo/vitro degradation or efficacy loss of biopharmaceuticals. However, a major challenge for MS analysis of deamidation of Asn-containing peptides in mAbs, is due to the fact that there is only a 1 Da mass shift between the native form (Asn residues) and deamidated forms (n-aspartyl (n-Asp) and isoaspartyl (isoAsp) residues with identical mass). Therefore, a chromatographic separation of the deamidated proteins and/or the peptides derived therefrom is needed prior to MS analysis. In this study, the monolithic column with various stationary phases, including reverse phase (RP), single phospholipid-functionalized and mixed phospholipid-functionalized monoliths, were prepared for the separation of the deamidation-sensitive signature peptide (IYPTNGYTR) of trastuzumab and its two deamidated products, n-Asp55 residue IYPTDGYTR and isoAsp55 residue IYPTisoDGYTR. Compared to the RP monolith, the phospholipid-functionalized monoliths provided mixed-mode interactions and exhibited better peak shape and separation selectivity. The effect of the parameters, including the type and concentration of buffer, temperature and pH value on the separation performance were investigated. Under the optimal conditions, the three peptides were fully separated on a mixed phosphocholine (PC) / phosphatidic acid (PA) functionalized monolith (poly (MDPC60PA40-co-EDMA)) due to the joint contribution of hydrophobic and electrostatic interactions. Therefore, the novel method based on the mixed phospholipids-functionalized monolithic column exhibited good potential for the analysis of deamidated peptides, which will be useful for the in-depth study of post-translational modifications of mAbs.


Assuntos
Amidas/química , Cromatografia por Troca Iônica/métodos , Peptídeos/isolamento & purificação , Fosfolipídeos/química , Acetatos/química , Sequência de Aminoácidos , Asparagina/química , Tampões (Química) , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Peptídeos/análise , Peptídeos/química , Temperatura Ambiente
12.
Se Pu ; 37(6): 666-670, 2019 Jun 08.
Artigo em Chinês | MEDLINE | ID: mdl-31152519

RESUMO

Sodium dodecyl sulfate capillary electrophoresis has become the mainstream method for purity analysis of monoclonal antibodies because of its advantages of fast and high resolution. Sample preparation has a significant impact on the purity detection of non-reduced monoclonal antibodies. In order to optimize sample preparation, the purity of monoclonal antibodies of different types and batches in sample buffers with iodoacetamide and N-ethyl maleimide as sulfhydryl sealants and at pH 6.0-9.0 was investigated. It was found that in the two types of sulfhydryl sealants, the high pH sample buffer could affect the sealing effect of the sulfhydryl sealant and produce more antibody fragments. Conversely, under the low pH condition, the antibody fragments were fewer and the purities of monoclonal antibodies were higher. Therefore, the sample buffer with pH 6.0 is the optimal preparation condition for the purity detection of non-reduced monoclonal antibodies.


Assuntos
Anticorpos Monoclonais/análise , Eletroforese Capilar , Tampões (Química) , Concentração de Íons de Hidrogênio , Dodecilsulfato de Sódio
13.
J Environ Manage ; 243: 12-21, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31077866

RESUMO

A vegetated buffer, barrier, or filter strip is a parcel of land that is designated to separate land used for agriculture from valued aquatic or terrestrial habitats. It exists partly with the intent to diffuse runoff and to impeded sediment, nutrients, pesticides, and other constituents from reaching off-site surface waters. Mandatory buffer implementation is regulated at various levels of government in North America - from the federal to the state and provincial levels, and by some municipalities and counties. To better understand the degree and breadth of oversight, we undertook a comprehensive search and review of vegetative buffer regulations across North America. We determined the width of buffer required, under what habitat or field conditions, for which pesticides, and application type, amongst other attributes. For ground application, margins ranged from 1 m to upwards of greater than 4000 m depending on protection goals, with some being compound specific and others being generally applied to all registered pesticides/compounds. These buffers tended to be used most often to protect surface water, groundwater (e.g. drinking water wells), and nearby sensitive crops, but the required distances are generally not consistent between jurisdictions, regardless of the stated protection goals. We recommend that a thorough science-based review take place, with input from relevant stakeholders, to harmonize vegetated buffer size for effective surface water protection where ecological, climatic, and agricultural conditions are sufficiently similar in North America.


Assuntos
Praguicidas , Poluentes Químicos da Água , Agricultura , Tampões (Química) , Canadá , América do Norte , Estados Unidos
14.
Pharm Res ; 36(7): 98, 2019 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-31087169

RESUMO

PURPOSE: To study the effect of mannitol or trehalose on the crystallization behavior of solutes in phosphate buffered saline (PBS) when the solutions were frozen and freeze-dried. METHODS: PBS (pH 7.5 at RT) either alone, or with trehalose (5% w/v) or mannitol (1% w/v), were frozen and characterized using low temperature differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and pH measurement. Freeze dried lyophiles were characterized by XRD. RESULTS: In the absence of cosolutes, upon freezing PBS, a pH shift of ~ 4 units was observed due to crystallization of Na2HPO4•12H2O. XRD indicated sequential crystallization of Na2HPO4•12H2O, NaCl•2H2O and KCl during cooling. When the frozen solutions were heated, two eutectics were observed - the first at ~ -24°C (ternary, NaCl•2H2O-KCl-ice) and the second at ~ -22°C (binary, NaCl•2H2O-ice). Trehalose completely inhibited buffer salt crystallization, whereas mannitol suppressed it partially thereby attenuating the magnitude of pH shift. The two eutectic meltings were also suppressed by the cosolutes. XRD of final lyophiles from PBS alone revealed peaks of anhydrous Na2HPO4, NaCl, and KCl. Trehalose rendered the lyophiles completely XRD amorphous, whereas in presence of mannitol, all the solutes except KH2PO4 crystallized. CONCLUSIONS: Freezing of PBS solution caused a pronounced pH shift due to selective crystallization of Na2HPO4•12H2O. The addition of trehalose or mannitol suppressed the buffer salt crystallization and attenuated the magnitude of pH shift. The potential instability of biologics due to pH shift in PBS, can be potentially mitigated with the cosolutes.


Assuntos
Manitol/química , Fosfatos/química , Solução Salina/química , Trealose/química , Tampões (Química) , Cristalização , Liofilização , Congelamento , Concentração de Íons de Hidrogênio , Cloreto de Potássio/química , Cloreto de Sódio/química , Temperatura Ambiente
15.
Aquat Toxicol ; 212: 120-127, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31103733

RESUMO

Ocean acidification (OA) has the potential to alter the bioavailability of pH sensitive metals contaminating coastal sediments, particularly copper, by changing their speciation in seawater. Hence OA may drive increased toxicity of these metals to coastal biota. Here, we demonstrate complex interactions between OA and copper on the physiology and toxicity responses of the sediment dwelling polychaete Alitta virens. Worm coelomic fluid pCO2 was not increased by exposure to OA conditions (pHNBS 7.77, pCO2 530 µatm) for 14 days, suggesting either physiological or behavioural responses to control coelomic fluid pCO2. Exposure to 0.25 µM nominal copper caused a decrease in coelomic fluid pCO2 by 43.3% and bicarbonate ions by 44.6% but paradoxically this copper-induced effect was reduced under near-future OA conditions. Hence OA appeared to 'buffer' the copper-induced acid-base disturbance. DNA damage was significantly increased in worms exposed to copper under ambient pCO2 conditions, rising by 11.1% compared to the worms in the no copper control, but there was no effect of OA conditions on the level of DNA damage induced by copper when exposed in combination. These interactions differ from the increased copper toxicity under OA conditions reported for several other invertebrate species. Hence this new evidence adds to the developing paradigm that species' physiology is key in determining the interactions of these two stressors rather than it purely being driven by the changes in metal chemistry under lower seawater pH.


Assuntos
Cobre/toxicidade , Poliquetos/efeitos dos fármacos , Água do Mar/química , Ácidos/farmacologia , Animais , Tampões (Química) , Dano ao DNA/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade
16.
Bioelectrochemistry ; 128: 100-108, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30959397

RESUMO

The work was aimed at the development of a biosensor array for the simultaneous determination of six solutes (glutamate, glucose, choline, acetylcholine, lactate, and pyruvate) in aqueous solutions. Enzymes selective for these substrates were immobilized on the surface of amperometric platinum disc electrodes and served as bioselective elements of a biosensor array. Direct enzymatic analysis by the developed biosensors provided high sensitivity to the tested substrates (limits of detection were 1-5 µM). The linear ranges of the biosensors were from 0.001-0.01 mM to 0.2-2.5 mM. The influence of solution pH, ionic strength and buffer capacity on the biosensor responses was investigated; the conditions for simultaneous operation of all the bioselective elements were optimized. The absence of any cross-influence of the substrates of enzymatic systems used was shown as well as a high selectivity of the biosensors and the absence of any impact of interfering substances (ascorbic acid, dopamine, cysteine, paracetamol). The developed biosensor array had good response reproducibility and storage stability. The array is suitable for rapid (0.5-1 min) and simple simultaneous determination of glutamate, glucose, choline, acetylcholine, lactate, and pyruvate in aqueous (biological) samples; furthermore, the creation of a single chip with six sensitive elements is possible as well as the addition of other biosensors.


Assuntos
Acetilcolina/análise , Técnicas Biossensoriais , Colina/análise , Técnicas Eletroquímicas/instrumentação , Eletrodos , Enzimas Imobilizadas/química , Glucose/análise , Ácido Glutâmico/análise , Ácido Láctico/análise , Ácido Pirúvico/análise , Tampões (Química) , Concentração de Íons de Hidrogênio , Limite de Detecção , Concentração Osmolar , Reprodutibilidade dos Testes
17.
Nat Commun ; 10(1): 1720, 2019 04 12.
Artigo em Inglês | MEDLINE | ID: mdl-30979890

RESUMO

ATP-dependent chromatin remodelling enzymes (remodellers) regulate DNA accessibility in eukaryotic genomes. Many remodellers reposition (slide) nucleosomes, however, how DNA is propagated around the histone octamer during this process is unclear. Here we examine the real-time coordination of remodeller-induced DNA movements on both sides of the nucleosome using three-colour single-molecule FRET. During sliding by Chd1 and SNF2h remodellers, DNA is shifted discontinuously, with movement of entry-side DNA preceding that of exit-side DNA. The temporal delay between these movements implies a single rate-limiting step dependent on ATP binding and transient absorption or buffering of at least one base pair. High-resolution cross-linking experiments show that sliding can be achieved by buffering as few as 3 bp between entry and exit sides of the nucleosome. We propose that DNA buffering ensures nucleosome stability during ATP-dependent remodelling, and provides a means for communication between remodellers acting on opposite sides of the nucleosome.


Assuntos
Adenosina Trifosfatases/metabolismo , Cromatina/química , Proteínas Cromossômicas não Histona/metabolismo , Proteínas de Ligação a DNA/metabolismo , DNA/análise , Nucleossomos/química , Proteínas de Saccharomyces cerevisiae/metabolismo , Trifosfato de Adenosina/química , Animais , Tampões (Química) , DNA Helicases/química , Transferência Ressonante de Energia de Fluorescência , Histonas/química , Humanos , Ligação Proteica , Saccharomyces cerevisiae/metabolismo , Xenopus
18.
Sci Total Environ ; 676: 11-17, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31029896

RESUMO

Anolyte acidification is inevitable in the operation of buffer-free microbial fuel cells (MFCs), which restricts the proliferation and metabolism of electroactive bacteria, and results in electric-power deterioration. The anodic metabolic end-products, inorganic carbons (IC), which are composed of H2CO3 (dissolved CO2), HCO3-, and CO32-, are ideal endogenous buffers, whereas the naturally accumulated IC are far from enough to prevent anolyte acidification. In this work, different volume ratios of the anolytes (10%, 30%, and 50%) were recycled to increase the IC concentrations of the single-chamber air-cathode buffer-free MFCs. Under anolyte recycling running mode, IC accumulation agreed with the SGompertz model and the fitting IC-asymptotic concentrations (ICAC) grew exponentially to 18.5 mM, 24.4 mM, and 32.8 mM as the anolyte recycling ratio increased from 10% to 30% and 50%. Self-buffering running can be realized when the anolyte recycling ratio exceeds 50% for the MFC feeding on 1 g·L-1 of acetate. The electric power for the 50% recycling scenario increased from the baseline control of 272.4 mW·m-2 to 628.5 mW·m-2. The coulombic efficiency (CE) was also apparently improved. This paper for the first time clarifies the accumulation law of endogenous IC buffers under anolyte partially recycling mode and their self-buffering effects.


Assuntos
Fontes de Energia Bioelétrica , Carbono/química , Bactérias , Tampões (Química) , Eletricidade , Eletrodos , Concentração de Íons de Hidrogênio
19.
ACS Appl Mater Interfaces ; 11(18): 16347-16356, 2019 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-31032616

RESUMO

We report new surface coatings that adhesively distinguish three breast epithelial cell lines (MCF-10A, MCF-7, and TMX2-28) when cell suspensions in buffer or breast milk are flowed over the coatings. We also report the selective capture of epithelial cells and rejection of Jurkat lymphocytes, with average selectivities exceeding 60 and captured cell purities often exceeding >99%. The surfaces achieve the dual goals of selective cell capture and resistance to fouling by proteins and other components of breast milk. The coatings do not rely on antibody targeting of cell surface markers but instead contain polycation chains embedded within a layer of end-tethered poly(ethylene glycol) (PEG) chains. The PEG, somewhat shielding the polycations, prevents surface fouling by proteins, nondesired cells, and other milk components, while the polycations produce electrostatic attractions that are heterogeneous on nanoscopic length scales. These electrostatic heterogeneities on the engineered coating, shown to produce curvature-selective particle capture in other studies, produce cell selectivity here. The ability of the engineered surfaces to discriminate these cell lines via an electrostatic driving force is remarkable, as the cells are of very similar surface charge as evidenced by their nearly identical ζ-potentials. The current surfaces, which likely distinguish cells based on their electrostatic surface landscape combined with other factors, adhesively distinguish cell lines that may differ only slightly in their expression of a surface marker, or cancer cells that minimally express EpCAM but which have different distributions of electrostatic charge on their surfaces. These surfaces are among the first to be documented for the compatibility of a polymer brush with human breast milk and may find use in technologies that capture cells from human breast milk or other complex fluids for cancer risk assessment.


Assuntos
Adesivos/farmacologia , Mama/efeitos dos fármacos , Linfócitos/efeitos dos fármacos , Leite Humano/química , Adesivos/química , Mama/citologia , Tampões (Química) , Molécula de Adesão da Célula Epitelial/genética , Células Epiteliais/química , Feminino , Expressão Gênica/efeitos dos fármacos , Humanos , Células Jurkat , Células MCF-7 , Polietilenoglicóis/química , Polímeros/química , Polímeros/farmacologia , Propriedades de Superfície
20.
Biol Lett ; 15(1): 20180583, 2019 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-30958214

RESUMO

Mechanisms underlying adaptation to rapid environmental change are issues in evolutionary biology. It is widely accepted that reduction in genetic diversity when suddenly exposed to an unfavourable environment limits the adaptive potential of populations. With growing empirical evidence that expression diversity is likely to increase in the new environment, the role that expression diversity plays in adaptation needs to be theorized. Here, we first established a negative exponential relationship between expression diversity and genetic diversity using a phenomenological differential equation. We then derived a complex trade-off relationship between the changes of expression and genetic diversity, which followed a combination of exponential functions. Furthermore, we found the increase in expression diversity could buffer the loss of adaptive potential as genetic diversity decreased to a certain extent. These theoretical deductions were validated by transcriptomic data of Miscanthus lutarioriparius grown in two experimental fields and supported by good fit and random simulation. These results suggest that increased expression diversity may compensate the loss of genetic diversity and allow the populations to maintain a certain level of phenotypic variation to cope with sudden environmental change. This may buffer the quick diminishing of adaptive potential and consequently increases the change of adaptation to the new environment.


Assuntos
Evolução Biológica , Variação Genética , Tampões (Química) , Poaceae , Seleção Genética , Transcriptoma
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