Academic literature on the topic 'ClyA Toxin'
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Journal articles on the topic "ClyA Toxin"
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Sathyanarayana, Pradeep, Satyaghosh Maurya, Amit Behera, Monisha Ravichandran, Sandhya S. Visweswariah, K. Ganapathy Ayappa, and Rahul Roy. "Cholesterol promotes Cytolysin A activity by stabilizing the intermediates during pore formation." Proceedings of the National Academy of Sciences 115, no. 31 (July 16, 2018): E7323—E7330. http://dx.doi.org/10.1073/pnas.1721228115.
Full textAbstract:
Pore-forming toxins (PFTs) form nanoscale pores across target membranes causing cell death. Cytolysin A (ClyA) from Escherichia coli is a prototypical α-helical toxin that contributes to cytolytic phenotype of several pathogenic strains. It is produced as a monomer and, upon membrane exposure, undergoes conformational changes and finally oligomerizes to form a dodecameric pore, thereby causing ion imbalance and finally cell death. However, our current understanding of this assembly process is limited to studies in detergents, which do not capture the physicochemical properties of biological membranes. Here, using single-molecule imaging and molecular dynamics simulations, we study the ClyA assembly pathway on phospholipid bilayers. We report that cholesterol stimulates pore formation, not by enhancing initial ClyA binding to the membrane but by selectively stabilizing a protomer-like conformation. This was mediated by specific interactions by cholesterol-interacting residues in the N-terminal helix. Additionally, cholesterol stabilized the oligomeric structure using bridging interactions in the protomer–protomer interfaces, thereby resulting in enhanced ClyA oligomerization. This dual stabilization of distinct intermediates by cholesterol suggests a possible molecular mechanism by which ClyA achieves selective membrane rupture of eukaryotic cell membranes. Topological similarity to eukaryotic membrane proteins suggests evolution of a bacterial α-toxin to adopt eukaryotic motifs for its activation. Broad mechanistic correspondence between pore-forming toxins hints at a wider prevalence of similar protein membrane insertion mechanisms.
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Bräuning, Bastian, and Michael Groll. "Structural and Mechanistic Features of ClyA-Like α-Pore-Forming Toxins." Toxins 10, no. 9 (August 23, 2018): 343. http://dx.doi.org/10.3390/toxins10090343.
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Recent technological advances have seen increasing numbers of complex structures from diverse pore-forming toxins (PFT). The ClyA family of α-PFTs comprises a broad variety of assemblies including single-, two- and three-component toxin systems. With crystal structures available for soluble subunits of all major groups in this extended protein family, efforts now focus on obtaining molecular insights into physiological pore formation. This review provides an up-to-date discussion on common and divergent structural and functional traits that distinguish the various ClyA family PFTs. Open questions of this research topic are outlined and discussed.
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Murase, Kazunori. "Cytolysin A (ClyA): A Bacterial Virulence Factor with Potential Applications in Nanopore Technology, Vaccine Development, and Tumor Therapy." Toxins 14, no. 2 (January 21, 2022): 78. http://dx.doi.org/10.3390/toxins14020078.
Full textAbstract:
Cytolysin A (ClyA) is a pore-forming toxin that is produced by some bacteria from the Enterobacteriaceae family. This review provides an overview of the current state of knowledge regarding ClyA, including the prevalence of the encoding gene and its transcriptional regulation, the secretion pathway used by the protein, and the mechanism of protein assembly, and highlights potential applications of ClyA in biotechnology. ClyA expression is regulated at the transcriptional level, primarily in response to environmental stressors, and ClyA can exist stably both as a soluble monomer and as an oligomeric membrane complex. At high concentrations, ClyA induces cytolysis, whereas at low concentrations ClyA can affect intracellular signaling. ClyA is secreted in outer membrane vesicles (OMVs), which has important implications for biotechnology applications. For example, the native pore-forming ability of ClyA suggests that it could be used as a component of nanopore-based technologies, such as sequencing platforms. ClyA has also been exploited in vaccine development owing to its ability to present antigens on the OMV surface and provoke a robust immune response. In addition, ClyA alone or OMVs carrying ClyA fusion proteins have been investigated for their potential use as anti-tumor agents.
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Roderer, Daniel, and Rudi Glockshuber. "Assembly mechanism of the α-pore–forming toxin cytolysin A from Escherichia coli." Philosophical Transactions of the Royal Society B: Biological Sciences 372, no. 1726 (June 19, 2017): 20160211. http://dx.doi.org/10.1098/rstb.2016.0211.
Full textAbstract:
The cytolytic toxin cytolysin A (ClyA) from Escherichia coli is probably one of the best-characterized examples of bacterial, α-pore–forming toxins (α-PFTs). Like other PFTs, ClyA exists in a soluble, monomeric form that assembles to an annular, homo-oligomeric pore complex upon contact with detergent or target membranes. Comparison of the three-dimensional structures of the 34 kDa monomer and the protomer in the context of the dodecameric pore complex revealed that ClyA undergoes one of the largest conformational transitions described for proteins so far, in which 55% of the residues change their position and 16% of the residues adopt a different secondary structure in the protomer. Studies on the assembly of ClyA revealed a unique mechanism that differs from the assembly mechanism of other PFTs. The rate-liming step of pore formation proved to be the unimolecular conversion of the monomer to an assembly-competent protomer, during which a molten globule-like off-pathway intermediate accumulates. The oligomerization of protomers to pore complexes is fast and follows a kinetic scheme in which mixtures of linear oligomers of different size are formed first, followed by very rapid and specific association of pairs of oligomers that can directly perform ring closure to the dodecameric pore complex. This article is part of the themed issue ‘Membrane pores: from structure and assembly, to medicine and technology’.
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Ludwig, Albrecht, Christine von Rhein, Susanne Bauer, Christian Hüttinger, and Werner Goebel. "Molecular Analysis of Cytolysin A (ClyA) in Pathogenic Escherichia coli Strains." Journal of Bacteriology 186, no. 16 (August 15, 2004): 5311–20. http://dx.doi.org/10.1128/jb.186.16.5311-5320.2004.
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ABSTRACT Cytolysin A (ClyA) of Escherichia coli is a pore-forming hemolytic protein encoded by the clyA (hlyE, sheA) gene that was first identified in E. coli K-12. In this study we examined various clinical E. coli isolates with regard to the presence and integrity of clyA. PCR and DNA sequence analyses demonstrated that 19 of 23 tested Shiga toxin-producing E. coli (STEC) strains, all 7 tested enteroinvasive E. coli (EIEC) strains, 6 of 8 enteroaggregative E. coli (EAEC) strains, and 4 of 7 tested enterotoxigenic E. coli (ETEC) strains possess a complete clyA gene. The remaining STEC, EAEC, and ETEC strains and 9 of the 17 tested enteropathogenic E. coli (EPEC) strains were shown to harbor mutant clyA derivatives containing 1-bp frameshift mutations that cause premature termination of the coding sequence. The other eight EPEC strains and all tested uropathogenic and new-born meningitis-associated E. coli strains (n = 14 and 3, respectively) carried only nonfunctional clyA fragments due to the deletion of two sequences of 493 bp and 204 or 217 bp at the clyA locus. Expression of clyA from clinical E. coli isolates proved to be positively controlled by the transcriptional regulator SlyA. Several tested E. coli strains harboring a functional clyA gene produced basal amounts of ClyA when grown under standard laboratory conditions, but most of them showed a clyA-dependent hemolytic phenotype only when SlyA was overexpressed. The presented data indicate that cytolysin A can play a role only for some of the pathogenic E. coli strains.
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Ludwig, Albrecht, Guido Völkerink, Christine von Rhein, Susanne Bauer, Elke Maier, Birgit Bergmann, Werner Goebel, and Roland Benz. "Mutations Affecting Export and Activity of Cytolysin A from Escherichia coli." Journal of Bacteriology 192, no. 15 (May 28, 2010): 4001–11. http://dx.doi.org/10.1128/jb.01283-09.
Full textAbstract:
ABSTRACT Cytolysin A (known as ClyA, HlyE, and SheA) is a cytolytic pore-forming protein toxin found in several Escherichia coli and Salmonella enterica strains. The structure of its water-soluble monomeric form and that of dodecameric ClyA pores is known, but the mechanisms of ClyA export from bacterial cells and of pore assembly are only partially understood. Here we used site-directed mutagenesis to study the importance of different regions of the E. coli ClyA protein for export and activity. The data indicate that ClyA translocation to the periplasm requires several protein segments located closely adjacent to each other in the “tail” domain of the ClyA monomer, namely, the N- and C-terminal regions and the hydrophobic sequence ranging from residues 89 to 101. Deletion of most of the “head” domain of the monomer (residues 181 to 203), on the other hand, did not strongly affect ClyA secretion, suggesting that the tail domain plays a particular role in export. Furthermore, we found that the N-terminal amphipathic helix αA1 of ClyA is crucial for the formation and the properties of the transmembrane channel, and hence for hemolytic activity. Several mutations affecting the C-terminal helix αG, the “β-tongue” region in the head domain, or the hydrophobic region in the tail domain of the ClyA monomer strongly impaired the hemolytic activity and reduced the activity toward planar lipid bilayer membranes but did not totally prevent formation of wild-type-like channels in these artificial membranes. The latter regions thus apparently promote membrane interaction without being directly required for pore formation in a lipid bilayer.
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von Rhein, Christine, Klaus-Peter Hunfeld, and Albrecht Ludwig. "Serologic Evidence for Effective Production of Cytolysin A in Salmonella enterica Serovars Typhi and Paratyphi A during Human Infection." Infection and Immunity 74, no. 11 (August 21, 2006): 6505–8. http://dx.doi.org/10.1128/iai.00779-06.
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ABSTRACT ClyASTy and ClyASPaA are closely related pore-forming cytolysins of Salmonella enterica serovars Typhi and Paratyphi A whose expression is strongly repressed under standard in vitro growth conditions. We show here that human infections by these pathogens cause a specific antibody response to ClyA, indicating effective toxin production during infection.
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Vaidyanathan, M. S., Pradeep Sathyanarayana, Prabal K. Maiti, Sandhya S. Visweswariah, and K. G. Ayappa. "Lysis dynamics and membrane oligomerization pathways for Cytolysin A (ClyA) pore-forming toxin." RSC Advances 4, no. 10 (2014): 4930. http://dx.doi.org/10.1039/c3ra45159c.
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Dingfelder, Fabian, Stephan Benke, Daniel Nettels, and Benjamin Schuler. "Mapping an Equilibrium Folding Intermediate of the Cytolytic Pore Toxin ClyA with Single-Molecule FRET." Journal of Physical Chemistry B 122, no. 49 (August 29, 2018): 11251–61. http://dx.doi.org/10.1021/acs.jpcb.8b07026.
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Huang, Jinbo, Zeyuan Guan, Liting Wan, Tingting Zou, and Ming Sun. "Crystal structure of Cry6Aa: A novel nematicidal ClyA-type α-pore-forming toxin from Bacillus thuringiensis." Biochemical and Biophysical Research Communications 478, no. 1 (September 2016): 307–13. http://dx.doi.org/10.1016/j.bbrc.2016.07.002.
Full textDissertations / Theses on the topic "ClyA Toxin"
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Феденко, Ю. М., Л. Ю. М’якушко, Ю. Патяка, and І. Печончик. "Сорбція йонів Pb2+ бентонітовими глинами українського походження." Thesis, Сумський державний університет, 2016. http://essuir.sumdu.edu.ua/handle/123456789/52777.
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Йони Pb2+ належать до токсичних речовин комплексної дії. Гранично допустима концентрація (ГДК) йонів Pb2+ у питній водопровідній воді (згідно ДСанПіН 2.2.4-171-10) становить 0,01 мг/дм3 [1]. Тому наукове обгрунтування і розробка нових та вдосконалення існуючих методів очищення води від йонів Pb2+ є актуальною задачею.
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Ganash, Magdah. "X-ray crystallographic and electron microscopy studies on members of the ClyA/Nhe family of the pore-forming toxins avian pathogenic E. coli cytolysin A and B. cereus non-hemolytic enterotoxin." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/3830/.
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Escherichia coli cytolysin A (ClyA, also known as hemolysin E, HlyE) is a 34 kDa cytolytic α-helical pore-forming toxin. The crystal structure of soluble monomeric E. coli K-12 ClyA was previously solved at high resolution and this showed that ClyA had a novel structure that had not previously been seen in the data bank of proteins. Avian pathogenic E. coli (APEC), strain JM4660 ClyA is 75% sequence identical to E. coli K-12 ClyA and has many significant similarities. However, two significant differences between them are that JM4660 ClyA pores are more homogeneous when observed by electron microscopy (EM), and JM4660 ClyA is more thermostable than E. coli K-12 ClyA. Consequently, JM4660 ClyA could be a good model system to investigate ClyA membrane interaction. The expression and purification of JM4660 ClyA was successful. Crystals were grown of the pore form, but so far diffract to about 7 Å resolution. Bacillus cereus Nhe is a complex, pore-forming toxin consisting of three related proteins: NheA (43 kDa), NheB (39 kDa), and NheC (40 kDa). It is able to lyse mammalian cells from several organisms including humans in both Agar and liquid media and all three components of Nhe are necessary for toxicity. NheA has only 22% identity with NheB and NheC and its binding is the final stage of pore formation. Nhe proteins have sequence identity to B. cereus Hbl proteins. A previous structure solution of HblB revealed a structural resemblance to E. coli ClyA. To date, no crystal structure of any Nhe protein has been available in either the soluble form or in the pore form. Therefore, the project aimed to resolve the crystal structures of Nhe proteins in their water-soluble forms. The expression and purification of NheA was very successful. NheA was crystallized using PEG3350 as a precipitant by the sitting-drop vapour-diffusion method. The crystals belonged to space group C2, with unit-cell parameters a = 308 Å, b = 58 Å, c = 172.4 Å, α = γ = 90° and β =110° and were estimated to contain 8 protein molecules per asymmetric unit. The three-dimensional crystal structure was solved at 2.05 Å resolution using Multi-wavelength anomalous dispersion (MAD) data sets. NheA is a rod-shopped structure. The main body is formed by a bundle of four helices, each at least 70 Å long and near the end of C terminal there is a extra fifth helix known as αG. NheA has two subdomains: the tail domain and the head domain that contains amphipathic α/β hairpin. The structure of NheA reveals strong structure similarity to ClyA and HblB, which further suggests that Nhe, Hbl and ClyA belong to the some novel family of toxins. In addition, B. cereus NheB expressed in B. subtilis strain JH642, was purified and crystallized. This thesis also presents the initial electron microscopy studies involving NheA and NheB pore formation.
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Avelino, Alzira Rocheteau. "Designing a Pore-Forming Toxin Cytolysin A (ClyA) Specific to Target Cancer Cells." 2014. https://scholarworks.umass.edu/masters_theses_2/67.
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Cytolysin A (ClyA) is a member of a class of proteins called pore-forming toxins (PFTs). ClyA is secreted by Gram-negative bacteria, and it attacks a number of mammalian cells by inserting into and forming channels within the cell membrane (Oscarsson J et al., 1999). It has been suggested that ClyA binds to cholesterol (Oscarsson J et al., 1999) and thus can insert into the membranes of many different cell types of eukaryotic origin. In our studies we propose to engineer a ClyA protein that can only attack a small subset of cell types. We propose to engineer ClyA that can be only activated when exposed to specific cell-surface proteases produced by a specific cell type. We ultimately want to target breast cancer cells that differentially secrete or express proteases such as matrix-metalloproteases (Stautz D et al., 2012; Zhang, M et al. 2013). To engineer this protein we took advantage of the N-terminus of ClyA. The N-terminus of ClyA, which is highly hydrophobic (Oscarsson J et al), undergoes a conformational change to insert into the target cell membrane (Oscarsson J et al). This conformational change allows ClyA to penetrate the target membrane to form a transmembrane domain of ClyA. The hydrophobic nature of lipid membranes makes it highly unfavorable for any charged residues to cross the membrane (Hunt J 1997). With this in mind, we hypothesize that negative charges inserted into the N-terminus of ClyA will inhibit it from inserting into the membrane. Thus, we mutated the N-terminus of the ClyA protein by inserting an inactivation site composed of negatively charged amino acids that we hypothesize would prevent insertion into the plasma membrane of the target cell. Once we confirmed that this construct was an inactive ClyA mutant, we inserted a thrombin cleavage site right after the inserted negative charges. This site should allow us to remove the negative charges once the protein is exposed to thrombin. Once the negative charges are removed, the protein should recover its activity. This approach will allow us to create a version of ClyA that is protease-switchable.
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Agrawal, Ayush. "Pore Forming Toxins : Unravelling Oligomerization Pathways and Related Kinetics." Thesis, 2016. http://etd.iisc.ac.in/handle/2005/4066.
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Pore forming toxins are a class of proteins secreted from a wide variety of pathogens. These toxins are implicated in several diseases such as cholera, anthrax, tuberculosis and food poisoning. The toxin proteins are secreted from the virulent source in a water soluble form. Upon binding to the plasma membrane the proteins undergo a sequence of oligomerization steps to form a functional pore that leads to cell death. Due to pore forming nature of these proteins, they are referred to as pore forming toxins (PFTs). Pore forming toxins are broadly classified into α and β pore forming toxins based on the secondary protein structure that interacts with the membrane. In this the-sis we are primarily interested in understanding the underlying kinetics and oligomerization pathways that govern pore formation for Cytolysin A (ClyA) which is an α toxin and Lysenin which belongs to a class of β pore forming toxins. Although structural aspects of PFTs have been widely investigated the kinetics of pore formation has received little attention.
Using fluorescent dye leakage experiments we develop a model that relates the oligomerization kinetics to the dye leakage function based on a Poisson process. Excellent predictions of the temporal evolution of the leakage are obtained for reversible sequential kinetics of pore formation. Non-sequential kinetics did not capture the observed data. An essential ingredient in the model is the inclusion of leakage through intermediate oligomers or ’arcs’ which are membrane inserted and capable of leakage. Inclusion of these intermediates al-lows us, for the first time, to capture both the short and long time components of the dye leakage function.
We obtain a forward oligomerization time constant of 5 s, whereas the backward time constant is about 200 s. Reversibility ensures a constant supply of the monomers on the membrane surface. The oligomerization time is found to be the slowest step in contrast to the conformational step reported in the literature. Our model predictions are consistent with the growing pore model for pore formation.
In the last part of the thesis we attempt to determine the structure of membrane inserted ClyA toxin molecules on supported membrane platforms using atomic force microscopy (AFM). The challenges associated with imaging these molecules and associated pore complexes will be discussed.
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Maurya, Satyaghosh. "Investigating Membrane Dynamics And Oligomerization Of Pore-forming Toxins Using Single-molecule Fluorescence Techniques." Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5711.
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The biological membrane is a thin fluidic matrix composed of a lipid bilayer that forms the
primary cellular barrier against the extracellular environment. The high-density of embedded
proteins and glycosylated molecules confer further complexity with unique specificities
for signalling and transport across the membrane. Many pathogenic bacteria have evolved
dedicated proteins, pore-forming toxins (PFTs), to form nanoscale ring-like pores on cellular
membranes that lead to cell lysis and death. However, it is challenging to study how PFTs
function due to the considerable heterogeneity in their assembly intermediates and their
complex interaction with lipid components. In this work, we have employed single-particle
tracking and single-molecule photobleaching to investigate the assembly pathway of ClyA
(a representative αPFT) on supported lipid bilayers (SLB). We show that cholesterol in the
membrane greatly enhances the ClyA lytic activity by stabilizing the membrane inserted
protomer intermediate and assisting in oligomerization by acting as a ’molecular glue’
between the protomer-protomer interfaces. We identify the role of different membrane-bound motifs of ClyA responsible for defining the initial membrane binding and the large
conformational change required to form the pore. In the concluding part, we show how
biomolecular assembly of PFTs can be enhanced in complex ways by crowded membrane
surfaces using polyethylene glycol (PEG) grafted to lipids as crowders. As the PEG crowder
transition from mushroom to an elongated polymer called brush regime, membrane-embedded
molecules display correlated changes in their mobility and biomolecular assembly. Overall,
this work elucidates how molecular and physical interactions modulate the biomolecular
assembly of PFTs on lipid bilayer membranes.
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Vaidyanathan, M. S. "Modeling Lysis Dynamcis Of Pore Forming Toxins And Determination Of Mechanical Properties Of Soft Materials." Thesis, 2012. https://etd.iisc.ac.in/handle/2005/2466.
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Pore forming toxins are known for their ability to efficiently form transmembrane pores which eventually leads to cell lysis. PFTs have potential applications in devel-oping novel drug and gene delivery strategies. Although structural aspects of many pore forming toxins have been studied, very little is known about the dynamics and subsequent rupture mechanisms. In the first part of the thesis, a combined experimental and modeling study to understand the lytic action of Cytolysin A (ClyA) toxins on red blood cells (RBCs) has been presented. Lysis experiments are carried out on a 1% suspension of RBCs for different initial toxin concentrations ranging from 100 – 500 ng/ml and the extent of lysis is monitored spectrophotometrically. Using a mean field approach, we propose a non – equilibrium adsorption-reaction model to quantify the rate of pore formation on the cell surface. By analysing the model in a pre-lysis regime, the number of pores per RBC to initiate rupture was found to lie between 400 and 800. The time constants for pore formation are estimated to lie between 1-25 s and monomer conformation time scales were found to be 2-4 times greater than the oligomerization times. Using this model, we are able to predict the extent of cell lysis as a function of the initial toxin concentration. Various kinetic models for oligomerization mechanism have been explored. Irreversible sequential kinetic model has the best agreement with the available experimental data. Subsequent to the mean field approach, a population balance model was also formulated.
The mechanics of cell rupture due to pore formation is poorly understood. Efforts to address this issue are concerned with understanding the changes in the membrane mechanical properties such as the modulus and tension in the presence of pores. The second part of the thesis is concerned with using atomic force microscopy to measure the mechanical properties of cells. We explore the possibility of employing tapping mode AFM (TM-AFM) to obtain the elastic modulus of soft samples. The dynamics of TM-AFM is modelled to predict the elastic modulus of soft samples, and predict optimal cantilever stiffness for soft biological samples. From experiments using TM-AFM on Nylon-6,6 the elastic modulus is predicted to lie between 2 and 5 GPa. For materials having elastic moduli in the range of 1– 20 GPa, the cantilever stiffness from simulations is found to lie in the range of 1 – 50 N/m. For soft biological samples, whose elastic moduli are in the range of 10-1000 kPa, a narrower range of cantilever stiffness (0.1 – 0.6 N/m), should be used.
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Vaidyanathan, M. S. "Modeling Lysis Dynamcis Of Pore Forming Toxins And Determination Of Mechanical Properties Of Soft Materials." Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2466.
Full textAbstract:
Pore forming toxins are known for their ability to efficiently form transmembrane pores which eventually leads to cell lysis. PFTs have potential applications in devel-oping novel drug and gene delivery strategies. Although structural aspects of many pore forming toxins have been studied, very little is known about the dynamics and subsequent rupture mechanisms. In the first part of the thesis, a combined experimental and modeling study to understand the lytic action of Cytolysin A (ClyA) toxins on red blood cells (RBCs) has been presented. Lysis experiments are carried out on a 1% suspension of RBCs for different initial toxin concentrations ranging from 100 – 500 ng/ml and the extent of lysis is monitored spectrophotometrically. Using a mean field approach, we propose a non – equilibrium adsorption-reaction model to quantify the rate of pore formation on the cell surface. By analysing the model in a pre-lysis regime, the number of pores per RBC to initiate rupture was found to lie between 400 and 800. The time constants for pore formation are estimated to lie between 1-25 s and monomer conformation time scales were found to be 2-4 times greater than the oligomerization times. Using this model, we are able to predict the extent of cell lysis as a function of the initial toxin concentration. Various kinetic models for oligomerization mechanism have been explored. Irreversible sequential kinetic model has the best agreement with the available experimental data. Subsequent to the mean field approach, a population balance model was also formulated.
The mechanics of cell rupture due to pore formation is poorly understood. Efforts to address this issue are concerned with understanding the changes in the membrane mechanical properties such as the modulus and tension in the presence of pores. The second part of the thesis is concerned with using atomic force microscopy to measure the mechanical properties of cells. We explore the possibility of employing tapping mode AFM (TM-AFM) to obtain the elastic modulus of soft samples. The dynamics of TM-AFM is modelled to predict the elastic modulus of soft samples, and predict optimal cantilever stiffness for soft biological samples. From experiments using TM-AFM on Nylon-6,6 the elastic modulus is predicted to lie between 2 and 5 GPa. For materials having elastic moduli in the range of 1– 20 GPa, the cantilever stiffness from simulations is found to lie in the range of 1 – 50 N/m. For soft biological samples, whose elastic moduli are in the range of 10-1000 kPa, a narrower range of cantilever stiffness (0.1 – 0.6 N/m), should be used.
Books on the topic "ClyA Toxin"
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Sengco, Mario Rhuel. The aggregation of clay minerals and marine microalgal cells: Physicochemical theory and implications for controlling harmful algal blooms. Woods Hole, Mass: Woods Hole Oceanographic Institution, 2001.
Find full textBook chapters on the topic "ClyA Toxin"
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Hunt, Stuart, Jeffrey Green, and Peter J. Artymiuk. "Hemolysin E (HlyE, ClyA, SheA) and Related Toxins." In Advances in Experimental Medicine and Biology, 116–26. New York, NY: Springer New York, 2010. http://dx.doi.org/10.1007/978-1-4419-6327-7_10.
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Ghosh, Bhaskar, and Dola Chakraborty. "Clay-Induced Antimicrobial and Antitoxic Mechanisms: How Do the Clays Protect Us from Pathogens and Toxins?" In Clay Minerals, 25–53. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-22327-3_2.
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Liu, Peng. "Organo-Clay Nanohybrid Adsorbents in the Removal of Toxic Metal Ions." In Nanomaterials for Environmental Protection, 249–68. Hoboken, NJ: John Wiley & Sons, Inc, 2014. http://dx.doi.org/10.1002/9781118845530.ch16.
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Ito, Hiroko, Harue Masuda, and Akihiko Oshima. "Concentrations of the Naturally-Derived Toxic Elements and Its Geochemical Characteristics of the Alluvial Marine Clay Layer of Osaka Plain, Japan." In Environmental Science and Engineering, 504–11. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-2221-1_54.
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Savchenko, I. A., E. Yanovska, Y. Polonska, L. Ol’khovik, D. Sternik, and O. Kychkyruk. "The Sorption Properties of Ukrainian Saponite Clay In Situ Modified of Poly[4-Methacroyloxy-(4′-Carboxy-2′-Nitro)-Azobenzene] to Toxic Metals Ions." In Springer Proceedings in Physics, 61–71. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-52268-1_5.
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Naz, A. "Nano Clay-Polymer Composite for Water Treatment." In Materials Research Foundations, 129–52. Materials Research Forum LLC, 2022. http://dx.doi.org/10.21741/9781644902035-6.
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The usage of clay polymer composites has increased in the past few decades. Due to extensive availability, wide surface areas, and good adsorption efficiency clay polymers are gaining popularity amongst researchers to remove wide range of organic as well as inorganic pollutants from effluents. This book chapter sheds light on the characteristics, occurrence, types and synthesis of clay minerals used for preparing nano-clay polymer composites. It also highlights the types, applicability and efficiencies of particular nano clay polymers for the removal of dyes, paints, nutrients, potentially toxic elements and pharmaceutical contaminants from wastewater.
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Bajpai, A. "Nontronite-Starch based Nano-Composites and Applications." In Materials Research Foundations, 153–82. Materials Research Forum LLC, 2022. http://dx.doi.org/10.21741/9781644902035-7.
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Polymer nano-composites consist of two or more constituents with at least one being of nanoscale dimension. Being naturally abundant, affordable, non-toxic and biocompatible, clay-based minerals and biopolymers are advantageous to afford eco-friendly nanocomposites, especially useful for biological applications. Starch, a common polysaccharide, finds traditional use in the food industry, and has recently become relevant in several advanced technologies. Nontronite, an iron rich smectite clay, still remains underexplored in the context of nanocomposite preparation. This book chapter attempts to provide a brief overview of syntheses and applications of nanocomposites based on nontronite, starch and polysaccharide-clay.
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Zaghloul, Ahmed, Ridouan Benhiti, Rachid Aziam, Abdeljalil Ait Ichou, Mhamed Abali, Amina Soudani, Fouad Sinan, Mohamed Zerbet, and Mohamed Chiban. "A Brief Comparative Study on Removal of Toxic Dyes by Different Types of Clay." In Dyes and Pigments - Novel Applications and Waste Treatment. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.95755.
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Increasing amount of organic dyes in the ecosystem particularly in wastewater has propelled the search for more efficient low-cost bio adsorbents. Different techniques have been used for the treatment of wastewater containing toxic dyes such as: biological degradation, oxidation, adsorption, reverse osmosis, and membrane filtration. Among all these processes mentioned, adsorption with low cost adsorbents has been recognized as one of the cost effective and efficient techniques for treatment of industrial wastewater from organic and inorganic pollutants. Clays as material adsorbents for the removal of various toxic dyes from aqueous solutions as potential alternatives to activated carbons has recently received widespread attention because of the environmental-friendly nature of clay materials. This chapter presents a comprehensive account of the techniques used for the removal of industrial cationic and anionic dyes from water during the last 10 years with special reference to the adsorption by using low cost materials in decontamination processes. Effects of different adsorption parameters on the performance of clays as adsorbents have been also discussed. Various challenges encountered in using clay materials are highlighted and a number of future prospects for the adsorbents are proposed.
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Jain, P. "In-situ Composite Formation by Polymerization on the Hectorite or other Clay Materials." In Materials Research Foundations, 1–23. Materials Research Forum LLC, 2022. http://dx.doi.org/10.21741/9781644902035-1.
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Clays are the naturally existing mineral having layered structures with at least one dimension in the nano-range that are economical and environment friendly. There exist two types of nanoclays, anionic and cationic, depending on the surface charge layered. Nanoclays have wide application in different areas for improving physical properties like heat resistance, mechanical strength and anticorrosion quality of the polymer matrix. Clay and its composite have promising applications including tissue engineering, petroleum, drug delivery, food packaging and enzyme immobilization. Due to their superior properties like flame retardancy, non-toxic, magnetic properties and large surface areas; hectorites and their composite are of great interest. The primary focus of this chapter is Composite Formation by in-situ polymerization of hectorite/clay materials and its application in different areas.
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Tetyana, P. "Cellulose based Nano-Composites and Applications." In Advanced Applications of Micro and Nano Clay, 236–53. Materials Research Forum LLC, 2022. http://dx.doi.org/10.21741/9781644901915-10.
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Cellulose is an abundant, naturally occurring and bio-degradable material that has been examined as a possible replacement for conventional materials such as plastics which are known to be toxic to the environment. Cellulose nanomaterials, which can be produced directly from cellulose, offer unique properties and structures that have proven useful for a myriad of applications globally. Currently, cellulose nanomaterials have found widespread use in numerous fields including the biomedical, pharmaceutical, packaging, and the food technology industries. Thus, this chapter reports on the properties of cellulose nanomaterials and cellulose nanocomposites and their use in various fields or industries.
Conference papers on the topic "ClyA Toxin"
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Burlakovs, Juris, Jovita Pilecka, Inga Grinfelde, and Ruta Ozola-Davidane. "Clay minerals and humic substances as landfill closure covering material constituents: first studies." In Research for Rural Development 2020. Latvia University of Life Sciences and Technologies, 2020. http://dx.doi.org/10.22616/rrd.26.2020.032.
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Soil and groundwater as the leachate may contaminate surrounding watersheds, thus different pollutants from closed dumps and landfills pose significant risks to human health and ecology. Pollution may lead to soil and water degradation however it might be diminished through sustainable dump site closure projects and processual management. Several decades of clays and clay minerals studies lead to modified clay composites concept that is one of the potential promising solutions for building the landfill covering material and serve as capping biocover layer at the same time. As humic substances are constituents of soil organic matter, pollutants can be sorbed on the surfaces of complex molecules. This kind of humic acid-clay mineral composite materials thus might become as low cost building material component - covering material. Construction of such layer are to be performed as a combination of clay-humic composites and landfill mined fine fraction of waste with small amendment of natural soil. Several hypotheses that are already proven has to be mentioned: a) Clay minerals produce composites with humic substances; 2) Clay-humic complexes reduce through sorption both organic and inorganic pollutants; 3) Low risk of toxic byproducts from landfill mined waste fine fraction can be the problem; 4) Such composites mostly would trap toxic contaminants (e.g., pharmaceuticals) found in reworked fine fraction of waste. The aim of the work is to provide alternative solution for landfill closure by giving theoretical considerations from multidisciplinary knowledge of environmental engineering, chemistry and waste management.
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Aukkhowong, Waraporn, and Jassada Sarasook. "Reducing Toxic Gases From Motorcycle Exhaust by Using Clay Compound Ceramics Catalytic Converter." In The 14th National Conference on Technical Education and The 9th International Conference on Technical Education. KMUTNB, Bangkok, Thailand, 2022. http://dx.doi.org/10.14416/c.fte.2022.06.016.
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Harrane, A., M. A. Belaouedj, R. Meghabar, M. Belbachir, Alberto D’Amore, Domenico Acierno, and Luigi Grassia. "POLYMERIZATION OF LACTIC ACID BY MAGHNITE-H[sup +] A NON-TOXIC MONTMORILLONITE CLAY CATALYST." In IV INTERNATIONAL CONFERENCE TIMES OF POLYMERS (TOP) AND COMPOSITES. AIP, 2008. http://dx.doi.org/10.1063/1.2989053.
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Gabriela Ene, Alexandra, Lucia Secareanu, Ovidiu Iordache, Mirela Blaga, and Cristina Lite. "Characterization Studies of A Commercial Blue Clay For Cosmetic Textiles With Antibacterial Activity." In 14th International Conference on Applied Human Factors and Ergonomics (AHFE 2023). AHFE International, 2023. http://dx.doi.org/10.54941/ahfe1003642.
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Since the beginning of the present century, tests have shown that some types of clay can present antibacterial activity. In addition, the clay considered for pharmaceutical and cosmetic products have been found to be non-toxic and non-irritating materials, therefore, the use of these types of clay for cosmetic and pharmaceutical purposes has increased in recent years. The above being said, different types of clay have been used over time due to their antibacterial properties, but the analytical methods for their characterization are just beginning to develop. This article is part of a study having as main objective the development of multifunctional antimicrobial textile materials to prevent fungal and bacterial proliferation, thus creating an antimicrobial shield for the human body, especially for blemish-prone skin. In this paperwork, a commercial blue clay was characterized through modern techniques. One of these techniques is X-ray Diffraction (XRD). Coupling SEM with an Energy Dispersive X-Ray detector (EDX), complete information of the morphology and elemental composition of the clay powder can be obtained. Additionally, a microbiological characterization was also performed in order to assess the anti fungal properties. Thus, the obtained results provided an overview of the main features of the selected blue clay. Further studies will be directed to the development of different types of clay-based dispersion and also for the characterization of different types of textile materials, in order to choose a "clay-textile" pair with improved antimicrobial activity.
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Khalil, Abdelrahman Khalil Abdelrazek, Abdelaziz Elgamouz, Muataz Ali Atieh, Abdallah Shanableh, and Tahar Laoui. "Processing and Characterization of UAE Clay Ceramic Membranes for Water Treatment Applications." In International Symposium on Engineering and Business Administration. Switzerland: Trans Tech Publications Ltd, 2023. http://dx.doi.org/10.4028/p-2rwsts.
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The scarcity of drinking water is currently a critical issue in many parts of the world. Providing clean/urgent longer limited to natural sources. Wastewater treatment has become an urgent necessity in many countries, particularly in the Middle East and North African regions characterized by a desert climate. Hence, the development of effective methods for wastewater treatment is vital to overcome this water shortage. The present study attempts to explore the use of local clay from the United Arab Emirates (UAE) to prepare porous ceramic membranes (flat disk shape) for the purpose of removing toxic heavy metals from contaminated water. Two types of ceramic membranes were prepared by powder metallurgy method; the first type was prepared by uniaxial compression of the clay powder with particle size ≤ 250 μm, followed by sintering. The second type of membrane was composed of an activated carbon/clay powder mixture at different ratios (0.5%, 3% w/w). The activated carbon was used as an agent to form porosity in the plain clay membrane. The activated carbon was found to affect the final characteristics of the flat disk membranes sintered at 1000°C. 3% w/w activated carbon/clay powder was found to induce 19% porosity in the flat disc. The flat disc membranes were also characterized by X-ray diffraction, and scanning electron microscopy, X-ray fluorescence. The plain clay and 3% w/w activated carbon membranes were tested for their efficiency for water permeation. The results proved that the UAE clay could be considered as a promising material for the fabrication of ceramic membranes for prospective use in the removal of water contaminated with heavy metals.
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Ghazali, Nurul Aimi, Shigemi Naganawa, Yoshihiro Masuda, Wan Asma Ibrahim, and Noor Fitrah Abu Bakar. "Eco-Friendly Drilling Fluid Deflocculant for Drilling High Temperature Well: A Review." In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-78149.
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Conventional clay-based drilling fluids often experienced difficulties in controlling the rheological properties, gelation, and filtration due to flocculation of clay at the temperature higher than 121°C. Deflocculant or thinner, one of the drilling fluid additives, serves a significant role in preventing the association of clay particles particularly in high temperature environments such as high-pressure and high-temperature (HPHT) deep-water drilling. Lignosulfonate has been commonly used in the industry as deflocculant for clay-based drilling fluids since the late 1950s as a replacement for Quebracho tannin. Degradation at the elevated temperature limits the usage of anionic polymer and lignosulfonate. In improving the stability of deflocculant at high temperature, lignosulfonate is admixed or reacted with chromium and iron compound to obtain ferro-chrome lignosulfonate whose temperature limit is approximately 190°C. While recent ferro-chrome lignosulfonate contains less chrome than in the past, development of more environmentally friendly and higher thermally stable deflocculant is still needed. In HPHT environment which requires high-density drilling fluid, a higher thermally-stable deflocculant is also valuable for barite sagging that becomes problematic at a temperature higher than 200°C. Several findings in the past development of adhesives show that addition of tannin improves the thermal stability of lignosulfonate. Tannin is a polyphenolic compound that is natural, non-toxic and biodegradable and can be found in various part of a vascular plant other than Quebracho. Lignosulfonate, on the other hand, is a byproduct of the paper pulping process. Tannin and lignosulfonate are cross-linked to obtain tannin–lignosulfonate for use as a high-temperature drilling fluid deflocculant. Tannin and lignin are the most abundant compounds extracted from biomass. The wide availability of tannin and lignosulfonate is an advantage from a manufacturing cost viewpoint. In this paper, an overview of drilling fluids, classification of drilling fluid, high temperature reservoir environment, and mechanisms of dispersion and deflocculation are presented. Further discussion on the potential development of eco-friendly tannin–lignosulfonate based drilling fluid system for the high temperature well development also presented.
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Duartey, K. O., A. K. Quainoo, and C. K. Darko. "Evaluation Studies of KCl and Amino Acid Mixtures for Clay Stabilization and Rheological Enhancement of Water-Based Fracturing Fluids." In SPE Nigeria Annual International Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/217118-ms.
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Summary Conventional stabilizers such as inorganic salts in water-based fluids are restricted for use in gas and oil shales drilling and hydraulic fracturing for drilling due to environmental, economic and performance concerns. For example, 2% use of KCl, a commonly used inorganic salt, contains an excess of 9500ppm chloride. This is considered high and toxic. Apart from environmental problems, KCl inhibiting solutions tend to negatively affect the rheology of the water-based fluids, posing a dilemma for industry operators. The clay and rheological stabilizing effects of KCl and amino acid mixes for hydraulic fracturing operations were investigated in this study. The stabilizing and rheological potentials of mixes of KCl and organic compounds have proven to be superior to the separate compounds in studies. The KCl was used in the study at safe quantities (1%) to prevent toxicity concerns. In this study, the inhibition potentials of KCl+ Arginine and KCl + Alanine solutions, mixed approximately at ecologically safe quantities, were tested at different bentonite wafers using M4600 Linear swell at 25°C and 1000psi in the work. Furthermore, rheological studies on bentonite-based suspensions were carried out using a high-precision Discovery Hybrid Rheometer (DHR-1). This was done to monitor the flow parameters of the inhibiting suspensions and their anti-swelling effects on the bentonite component of the prepared fracturing fluid. The effects of the mixtures were also compared to that of KCl, Arginine and Alanine inhibition solutions. Herschel-Bulkley's model was also used to determine the flow characteristics. After 24 hours of testing, the swelling findings reveal that KCl+ Arginine/KCl + Alanine treated fracturing fluids significantly affect the clay stabilization and rheological properties of the fracturing fluid. The study provides basic information on the inhibition potentials of KCl and natural amino acid mixtures in water-based fracturing fluids for clean clay stabilization.
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Beites, Steven. "Performative Aesthetics: An Exploration into DLT-Ceramic Composite Wall Assemblies." In 108th Annual Meeting Proceedings. ACSA Press, 2020. http://dx.doi.org/10.35483/acsa.am.108.2.
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The paper presents the early development of a novel mass timber-ceramic wall assembly that speaks to the importance of sustainable, performative and aesthetic potentials within the built environment. The work seeks to broaden the extensive body of research conducted on the robotic additive manufacturing of customized ceramic clay printing for large scale construction, exploring the possibilities of clay for its performative and formal capacity. It employs the use of an industrial robotic platform not as a device for automation, but for its ability to produce unique elements through a craft-based methodology in search of variability and specificity. Recognizing the limitation of ceramics as a load bearing material, it seeks to uncover its potential when combined with mass timber. As a result, dowel-laminated timber (DLT) is explored for its numerous advantages including structural efficiency, low toxic manufacturing processes, its inherent renewability and speed of construction. With the renewed interest in mass timber structures in recent years, we are nonetheless confronted with the realities of this unique natural material. Being both anisotropic and hygroscopic, wood’s inherent moisture-storage capacity makes it susceptible to water and air infiltration, vapor migration and condensation (Gagnon et al. 2013). Whether it be dowel-laminated or cross-laminated, timber’s sensitivity to moisture and its vulnerability to the elements renders itself unsuitable as a cladding application. Responding to this need, traditional cladding solutions for mass timber assemblies generally do not offer sustainable alternatives nor do they provide heightened aesthetic interest. As a result, the paper explores the production of material effects that go beyond superficiality by addressing the shortcomings of exposed mass timber wall assemblies through the development of a protective ceramic ventilated façade system that combines ornamental effects with performative criteria.
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Ben Giuma, Laila Houd, and Muna Hassan Bek. "MICROSTRUCTURE, MINERALOGY AND PHYSICAL PROPERTIES OF KAOLIN & METAKAOLIN GEOPOLYMERS USED FOR SOLIDIFICATION AND STABILIZATION OF OIL AND GAS DRILLING WASTE OPERATIONS." In 22nd International Multidisciplinary Scientific GeoConference 2022. STEF92 Technology, 2022. http://dx.doi.org/10.5593/sgem2022v/3.2/s06.32.
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The production of oil and gas includes drilling a number of wells for exploration or production activities. During drilling operations, large volumes of drilling fluids are used to facilitate the process. In Libya, after completion of drilling operations drill cuttings and waste drilling fluids are typically discharged close to the oil fields without treatment. This can result in negative ecological impacts on the surrounding environment e.g. through infiltration of toxic constituents into soils and underground waters. In this work, the sustainable approaches were examined to test their suitability for use in Libyan Desert. The solidification/ stabilisation of drilling waste via geopolymerisation approach was tested using natural kaolin clay. The ability of the geopolymers to stabilise drilling waste by immobilising heavy metals and encapsulating hydrocarbons was evaluated through systematic experiments employing both macro properties and microstructure studies to assess: (i) the transformation of raw materials into cementitious materials; (ii) changes in physical and mechanical properties, (iii) the role of additives in enhancing the degree of geopolymerisation (iv) the leachability of solidified wastegeopolymers produced. The research has resulted in a number of key conclusions related to the feasibility of using Kaolin based geopolymers to stabilise the drilling waste generated from oil and gas industry in Libya. It is found that (S/S) systems composed from kaolin-waste geopolymer able to reduce the contaminants leachability by both physical (adsorption or encapsulation) and chemical (fixation) means, and it is possible to use Kaolin as a sustainable alternative for Portland cement in S/S system to convert the hazardous waste into inert or nonreactive hazardous waste acceptable for selected in-situ environmental engineering applications. The solidified geopolymer matrix found adequate to the requirements of sustainable waste management options such as safe landfill, reuse and recycle in the place of the generation which offering a sustainable, cost-effective approach that brings environmental and economic benefits.
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Schindler, Rob, Sean Comber, and Andrew Manning. "METAL POLLUTANT PATHWAYS IN COHESIVE COASTAL CATCHMENTS: INFLUENCE OF FLOCCULATION ON PARTITIONING AND FLUX." In GEOLINKS International Conference. SAIMA Consult Ltd, 2020. http://dx.doi.org/10.32008/geolinks2020/b2/v2/09.
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Potentially toxic metals (PTMs) dispersed within catchments from land-based sources pose serious, long-term threats to aquatic ecology and human health. Their chemical state or form affects the potential for transportation and bioavailability and ultimate environmental fate. PTMs are transported either as (1) particulates adsorbed onto sediments, or 2) solutes in groundwater and open channel flow. Cohesive sediment occupies a major part of the world’s coastlines. PTMs are readily sorbed onto clay/silt and consequently particulate-borne PTMs dominate in estuaries and coastal waters. Sediments also represent a considerable ‘sink’ of contaminants which can be periodically remobilized. The role of suspended particulates in the uptake, release, and transport of heavy metals is thus a crucial link in understanding PTM dispersion in these environments. Cohesive sediment is subject to flocculation which dictates the behaviour of suspended sediment. PTM partitioning, flocculation and particulate-borne PTM dynamics are spatially and temporally variable in response to a complex array of inter-related physical and chemical factors exhibited within tidal catchments. However, knowledge of the dispersion and accumulation of both particulate and soluble forms of PTMs within cohesive coastal catchments is limited by little understanding of the association of PTMs with flocculated sediments and their subsequent deposition. This study investigates the influence of changing hydrodynamics and salinities to reveal the partitioning coefficients (Kp) and PTM settling flux (PTMSF) for different spatial and temporal locations within an idealized mesotidal catchment. The data show that the ratio of soluble and particulate-borne PTMs are dependent on salinity and flocculation, and that PTMSF is dependent upon partitioning and flocculation dynamics. Kp is largely dictated by salinity, but floc size and suspended particulate matter concentration (SPMC) are also influential, particular for PTMs with low chloride complexation and in freshwater. PTMSF is a function of Kp, floc size and settling velocity and varies by up to 3 orders of magnitude in response to changing environmental conditions. Findings will improve our ability to predict and monitor contaminant transport for PTMs generated by industries such as agriculture, mining, fisheries, aquaculture & marine engineers. They can be incorporated in existing decision making tools, and help improve numerical modelling parameteristion, to maintain environmental quality standards and limit the impacts of bioavailability of metals in aquatic environment.