| 1. |
- Cai, Yixiao, et al.
(författare)
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Changes in secondary structure of alpha-synuclein during oligomerization induced by reactive aldehydes
- 2015
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 464:1, s. 336-341
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Tidskriftsartikel (refereegranskat)abstract
- The oxidative stress-related reactive aldehydes 4-hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE) have been shown to promote formation of alpha-synuclein oligomers in vitro. However, the changes in secondary structure of alpha-synuclein and the kinetics of the oligomerization process are not known and were the focus of this study. Size exclusion chromatography showed that after 1 h of incubation, HNE induced the formation of an oligomeric alpha-synuclein peak with a molecular weight of about similar to 2000 kDa, which coincided with a decreasing similar to 50 kDa monomeric peak. With prolonged incubation (up to 24 h) the oligomeric peak became the dominating molecular species. In contrast, in the presence of ONE, a similar to 2000 oligomeric peak was exclusively observed after 15 min of incubation and this peak remained constant with prolonged incubation. Western blot analysis of HNE-induced alpha-synuclein oligomers showed the presence of monomers (15 kDa), SDS-resistant low molecular (30-160 kDa) and high molecular weight oligomers (>= 260 kDa), indicating that the oligomers consisted of both covalent and non-covalent protein. In contrast, ONE-induced alpha-synuclein oligomers only migrated as covalent cross-linked high molecular-weight material (>= 300 kDa). Both circular dichroism (CD) and Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy showed that the formation of HNE- and ONE-induced oligomers coincided with a spectral change from random coil to beta-sheet. However, ONE-induced alpha-synuclein oligomers exhibited a slightly higher degree of beta-sheet. Taken together, our results indicate that both HNE and ONE induce a change from random coil to beta-sheet structure that coincides with the formation of alpha-synuclein oligomers; albeit through different kinetic pathways depending on the degree of cross-linking. (C) 2015 Elsevier Inc. All rights reserved.
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| 2. |
- Ericsson, Daniel J., et al.
(författare)
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X-Ray structure of Candida antarctica lipase A shows a novel lid structure and a likely mode of interfacial activation
- 2008
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Ingår i: Journal of Molecular Biology. - : Elsevier. - 0022-2836 .- 1089-8638. ; 376:1, s. 109-119
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Tidskriftsartikel (refereegranskat)abstract
- In nature, lipases (EC 3.1.1.3) catalyze the hydrolysis of triglycerides to form glycerol and fatty acids. Under the appropriate conditions, the reaction is reversible, and so biotechnological applications commonly make use of their capacity for esterification as well as for hydrolysis of a wide variety of compounds. In the present paper, we report the X-ray structure of lipase A from Candida antarctica, solved by single isomorphous replacement with anomalous scattering, and refined to 2.2-Å resolution. The structure is the first from a novel family of lipases. Contrary to previous predictions, the fold includes a well-defined lid as well as a classic α/β hydrolase domain. The catalytic triad is identified as Ser184, Asp334 and His366, which follow the sequential order considered to be characteristic of lipases; the serine lies within a typical nucleophilic elbow. Computer docking studies, as well as comparisons to related structures, place the carboxylate group of a fatty acid product near the serine nucleophile, with the long lipid tail closely following the path through the lid that is marked by a fortuitously bound molecule of polyethylene glycol. For an ester substrate to bind in an equivalent fashion, loop movements near Phe431 will be required, suggesting the primary focus of the conformational changes required for interfacial activation. Such movements will provide virtually unlimited access to solvent for the alcohol moiety of an ester substrate. The structure thus provides a basis for understanding the enzyme's preference for acyl moieties with long, straight tails, and for its highly promiscuous acceptance of widely different alcohol and amine moieties. An unconventional oxyanion hole is observed in the present structure, although the situation may change during interfacial activation
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| 3. |
- Fagerqvist, Therese, et al.
(författare)
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Monoclonal antibodies selective for α-synuclein oligomers/protofibrils recognize brain pathology in Lewy body disorders and α-synuclein transgenic mice with the disease-causing A30P mutation
- 2013
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Ingår i: Journal of Neurochemistry. - : Wiley-Blackwell. - 0022-3042 .- 1471-4159. ; 126:1, s. 131-144
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Tidskriftsartikel (refereegranskat)abstract
- Inclusions of intraneuronal alpha-synuclein (-synuclein) can be detected in brains of patients with Parkinson's disease and dementia with Lewy bodies. The aggregation of -synuclein is a central feature of the disease pathogenesis. Among the different -synuclein species, large oligomers/protofibrils have particular neurotoxic properties and should therefore be suitable as both therapeutic and diagnostic targets. Two monoclonal antibodies, mAb38F and mAb38E2, with high affinity and strong selectivity for large -synuclein oligomers were generated. These antibodies, which do not bind amyloid-beta or tau, recognize Lewy body pathology in brains from patients with Parkinson's disease and dementia with Lewy bodies and detect pathology earlier in -synuclein transgenic mice than linear epitope antibodies. An oligomer-selective sandwich ELISA, based on mAb38F, was set up to analyze brain extracts of the transgenic mice. The overall levels of -synuclein oligomers/protofibrils were found to increase with age in these mice, although the levels displayed a large interindividual variation. Upon subcellular fractionation, higher levels of -synuclein oligomers/protofibrils could be detected in the endoplasmic reticulum around the age when behavioral disturbances develop. In summary, our novel oligomer-selective -synuclein antibodies recognize relevant pathology and should be important tools to further explore the pathogenic mechanisms in Lewy body disorders. Moreover, they could be potential candidates both for immunotherapy and as reagents in an assay to assess a potential disease biomarker.
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| 4. |
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| 5. |
- Kasrayan, Alex, et al.
(författare)
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Enhancement by effectors and substrate nucleotides of R1-R2 interactions in Escherichia coli class Ia ribonucleotide reductase.
- 2004
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Ingår i: J Biol Chem. - 0021-9258. ; 279:30, s. 31050-7
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Ribonucleotide reductases are a family of essential enzymes that catalyze the reduction of ribonucleotides to their corresponding deoxyribonucleotides and provide cells with precursors for DNA synthesis. The different classes of ribonucleotide reductase are distinguished based on quaternary structures and enzyme activation mechanisms, but the components harboring the active site region in each class are evolutionarily related. With a few exceptions, ribonucleotide reductases are allosterically regulated by nucleoside triphosphates (ATP and dNTPs). We have used the surface plasmon resonance technique to study how allosteric effects govern the strength of quaternary interactions in the class Ia ribonucleotide reductase from Escherichia coli, which like all class I enzymes has a tetrameric alpha(2) beta(2) structure. The component alpha(2)called R1 harbors the active site and two types of binding sites for allosteric effector nucleotides, whereas the beta(2) component called R2 harbors the tyrosyl radical necessary for catalysis. Our results show that only the known allosteric effector nucleotides, but not non-interacting nucleotides, promote a specific interaction between R1 and R2. Interestingly, the presence of substrate together with allosteric effector nucleotide strengthens the complex 2-3 times with a similar free energy change as the mutual allosteric effects of substrate and effector nucleotide binding to protein R1 in solution experiments. The dual allosteric effects of dATP as positive allosteric effector at low concentrations and as negative allosteric effector at high concentrations coincided with an almost 100-fold stronger R1-R2 interaction. Based on the experimental setup, we propose that the inhibition of enzyme activity in the E. coli class Ia enzyme occurs in a tight 1:1 complex of R1 and R2. Most intriguingly, we also discovered that thioredoxin, one of the physiological reductants of ribonucleotide reductases, enhances the R1-R2 interaction 4-fold.
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| 6. |
- Kasrayan, Alex, et al.
(författare)
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Prediction of the Candida antarctica lipase A protein structure by comparative modeling and site-directed mutagenesis
- 2007
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Ingår i: ChemBioChem. - : Wiley. - 1439-4227 .- 1439-7633. ; 8:12, s. 1409-1415
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Tidskriftsartikel (refereegranskat)abstract
- A number of model structures of the CalA suggested by comparative modeling were tested by site-directed mutagenesis. Enzyme variants were created where amino acids predicted to play key roles for the lipase activity in the different models were replaced by an inert amino acid (alanine). The results from activity measurements of the overproduced and purified mutant enzymes indicate a structure where the active site consists of amino acid residues Ser184, His366, and Asp334 and in which there is no lid. This model can be used for future targeted modifications of the enzyme to obtain new substrate acceptance, better thermostability, and higher enantioselectivity.
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| 7. |
- Kasrayan, Alex, 1973-
(författare)
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Reaction Mechanism and Allosteric Regulation of Class Ia Ribonucleotide Reductase from Escherichia coli
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ribonculeotide reductase (RNR) plays a key role in catalysing a reaction that provides all living organisms with building blocks for DNA. The RNR enzyme catalyses the conversion of ribonucleotides to their corresponding deoxyribonucleotides, by using free radical chemistry. The class Ia enzyme from Escherichia coli is composed of two components, R1 and R2 proteins. Both components are required for the catalytic reaction. The R2 protein contains a stable tyrosyl free radical, which is directly involved in the catalysis. The R1 protein, contains the active site and two different allosteric sites, which are responsible for regulating the enzyme activity and its substrate specificity.An evolutionary conserved active site residue, Asn437, was studied. Employing site directed mutagensis it was shown that the Asn437 is essential for the catalytic reaction. Also using biophysical methods, it was shown that the Asn437 residue participates in the later part of the catalytic reaction.By using protein engineering, two conserved overall activity residues His59 and His88 were shown to be involved in the allosteric regulation of enzymatic activity. Furthermore, it was shown by biosensor technique (BIAcore) that the His59 and His88 participate in a communication network that regulates the binding affinity between the R1 and R2 components in response to the presence of certain allosteric effectors.The influence of the allosteric effectors and substrate nucleotides on the wild type R1/R2 interaction was investigated using biosensor technique. The presence of allosteric effectors strengthened the affinity between the components R1 and R2 as compared to the affinity in the absence of effectors. Interestingly, when both allosteric effectors and substrate nucleotides were present, the affinity between the R1 and R2 components was noticeably stronger as compared to the situations where only the allosteric effector was present.Finally, the residues located in the interaction area of the dimeric R1 protein from E. coli were studied. The aim was to understand their importance for the formation of the active dimeric form of R1. Interestingly, slight alterations of the chemical properties of single side chains resulted in drastic changes in dimer stability, indicating the importance of their interaction ability for dimer formation.
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| 8. |
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| 9. |
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| 10. |
- Larsson-Birgander, Pernilla, et al.
(författare)
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Mutant R1 proteins from Escherichia coli class Ia ribonucleotide reductase with altered responses to dATP inhibition.
- 2004
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Ingår i: J Biol Chem. - 0021-9258. ; 279:15, s. 14496-501
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Aerobic ribonucleotide reductase from Escherichia coli regulates its level of activity by binding of effectors to an allosteric site in R1, located to the proposed interaction area of the two proteins that comprise the class I enzyme. Activity is increased by ATP binding and decreased by dATP binding. To study the mechanism governing this regulation, we have constructed three R1 proteins with mutations at His-59 in the activity site and one R1 protein with a mutation at His-88 close to the activity site and compared their allosteric behavior to that of the wild type R1 protein. All mutant proteins retained about 70% of wild type enzymatic activity. We found that if residue His-59 was replaced with alanine or asparagine, the enzyme lost its normal response to the inhibitory effect of dATP, whereas the enzyme with a glutamine still managed to elicit a normal response. We saw a similar result if residue His-88, which is proposed to hydrogen-bond to His-59, was replaced with alanine. Nucleotide binding experiments ruled out the possibility that the effect is due to an inability of the mutant proteins to bind effector since little difference in binding constants was observed for wild type and mutant proteins. Instead, the interaction between proteins R1 and R2 was perturbed in the mutant proteins. We propose that His-59 is important in the allosteric effect triggered by dATP binding, that the conserved hydrogen bond between His-59 and His-88 is important for the communication of the allosteric effect, and that this effect is exerted on the R1/R2 interaction.
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| 11. |
- Larsson Birgander, Pernilla, et al.
(författare)
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Nucleotide-dependent formation of catalytically competent dimers from engineered monomeric ribonucleotide reductase protein R1
- 2005
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 280:15, s. 14997-15003
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Tidskriftsartikel (refereegranskat)abstract
- Each catalytic turnover by aerobic ribonucleotide reductase requires the assembly of the two proteins, R1 (α2) and R2 (β2), to produce deoxyribonucleotides for DNA synthesis. The R2 protein forms a tight dimer, whereas the strength of the R1 dimer differs between organisms, being monomeric in mouse R1 and dimeric in Escherichia coli. We have used the known E. coli R1 structure as a framework for design of eight different mutations that affect the helices and proximal loops that comprise the dimer interaction area. Mutations in loop residues did not affect dimerization, whereas mutations in the helices had very drastic effects on the interaction resulting in monomeric proteins with very low or no activity. The monomeric N238A protein formed an interesting exception, because it unexpectedly was able to reduce ribonucleotides with a comparatively high capacity. Gel filtration studies revealed that N238A was able to dimerize when bound by both substrate and effector, a result in accordance with the monomeric R1 protein from mouse. The effects of the N238A mutation, fit well with the notion that E. coli protein R1 has a comparatively small dimer interaction surface in relation to its size, and the results illustrate the stabilization effects of substrates and effectors in the dimerization process. The identification of key residues in the dimerization process and the fact that there is little sequence identity between the interaction areas of the mammalian and the prokaryotic enzymes may be of importance in drug design, similar to the strategy used in treatment of HSV infection.
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| 12. |
- Lindström, Veronica, et al.
(författare)
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Extensive uptake of α-synuclein oligomers in astrocytes results in sustained intracellular deposits and mitochondrial damage
- 2017
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Ingår i: Molecular and Cellular Neuroscience. - : Elsevier BV. - 1044-7431 .- 1095-9327. ; 82, s. 143-156
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Tidskriftsartikel (refereegranskat)abstract
- The presence of Lewy bodies, mainly consisting of aggregated α-synuclein, is a pathological hallmark of Parkinson's disease (PD) and dementia with Lewy bodies (DLB). The α-synuclein inclusions are predominantly found in neurons, but also appear frequently in astrocytes. However, the pathological significance of α-synuclein inclusions in astrocytes and the capacity of glial cells to clear toxic α-synuclein species remain unknown. In the present study we investigated uptake, degradation and toxic effects of oligomeric α-synuclein in a co-culture system of primary neurons, astrocytes and oligodendrocytes. Alpha-synuclein oligomers were found to co-localize with the glial cells and the astrocytes were found to internalize particularly large amounts of the protein. Following ingestion, the astrocytes started to degrade the oligomers via the lysosomal pathway but, due to incomplete digestion, large intracellular deposits remained. Moreover, the astrocytes displayed mitochondrial abnormalities. Taken together, our data indicate that astrocytes play an important role in the clearance of toxic α-synuclein species from the extracellular space. However, when their degrading capacity is overburdened, α-synuclein deposits can persist and result in detrimental cellular processes.
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| 13. |
- Nordström, Eva, et al.
(författare)
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ABBV-0805, a novel antibody selective for soluble aggregated alpha-synuclein, prolongs lifespan and prevents buildup of alpha-synuclein pathology in mouse models of Parkinson's disease
- 2021
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Ingår i: Neurobiology of Disease. - : Elsevier. - 0969-9961 .- 1095-953X. ; 161
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Tidskriftsartikel (refereegranskat)abstract
- A growing body of evidence suggests that aggregated alpha-synuclein, the major constituent of Lewy bodies, plays a key role in the pathogenesis of Parkinson's disease and related alpha-synucleinopathies. Immunotherapies, both active and passive, against alpha-synuclein have been developed and are promising novel treatment strategies for such disorders. Here, we report on the humanization and pharmacological characteristics of ABBV-0805, a monoclonal antibody that exhibits a high selectivity for human aggregated alpha-synuclein and very low affinity for monomers. ABBV-0805 binds to a broad spectrum of soluble aggregated alpha-synuclein, including small and large aggregates of different conformations. Binding of ABBV-0805 to pathological alpha-synuclein was demonstrated in Lewy body-positive post mortem brains of Parkinson's disease patients. The functional potency of ABBV-0805 was demonstrated in several cellular assays, including Fc gamma-receptor mediated uptake of soluble aggregated alpha-synuclein in microglia and inhibition of neurotoxicity in primary neurons. In vivo, the murine version of ABBV-0805 (mAb47) displayed significant dose dependent decrease of alpha-synuclein aggregates in brain in several mouse models, both in prophylactic and therapeutic settings. In addition, mAb47 treatment of alpha-synuclein transgenic mice resulted in a significantly prolonged survival. ABBV-0805 selectively targets soluble toxic alpha-synuclein aggregates with a picomolar affinity and demonstrates excellent in vivo efficacy. Based on the strong preclinical findings described herein, ABBV-0805 has been progressed into clinical development as a potential disease-modifying treatment for Parkinson's disease.
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| 14. |
- Näsström, Thomas, et al.
(författare)
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The lipid peroxidation products 4-oxo-2-nonenal and 4-hydroxy-2-nonenal promote the formation of α-synuclein oligomers with distinct biochemical, morphological, and functional properties
- 2011
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Ingår i: Free Radical Biology & Medicine. - : Elsevier BV. - 0891-5849 .- 1873-4596. ; 50:3, s. 428-437
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Tidskriftsartikel (refereegranskat)abstract
- Oxidative stress has been implicated in the etiology of neurodegenerative disorders with alpha-synuclein pathology. Lipid peroxidation products such as 4-oxo-2-nonenal (ONE) and 4-hydroxy-2-nonenal (HNE) can covalently modify and structurally alter proteins. Herein, we have characterized ONE- or HNE-induced alpha-synuclein oligomers. Our results demonstrate that both oligomers are rich in beta-sheet structure and have a molecular weight of about 2000 kDa. Atomic force microscopy analysis revealed that ONE-induced alpha-synuclein oligomers were relatively amorphous, with a diameter of 40-80 nm and a height of 4-8 nm. In contrast, the HNE-induced alpha-synuclein oligomers had a protofibril-like morphology with a width of 100-200 nm and a height of 2-4 nm. Furthermore, neither oligomer type polymerized into amyloid-like fibrils despite prolonged incubation. Although more SDS and urea stable, because of a higher degree of cross-linking, ONE-induced alpha-synuclein oligomers were less compact and more sensitive to proteinase K treatment. Finally, both ONE- and HNE-induced alpha-synuclein oligomers were cytotoxic when added exogenously to a neuroblastoma cell line, but HNE-induced alpha-synuclein oligomers were taken up by the cells to a significantly higher degree. Despite nearly identical chemical structures, ONE and HNE induce the formation of off-pathway alpha-synuclein oligomers with distinct biochemical, morphological, and functional properties.
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| 15. |
- Sandström, Anders G., et al.
(författare)
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Directed evolution of Candida antarctica lipase A using an episomaly replicating yeast plasmid
- 2009
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Ingår i: Protein Engineering Design & Selection. - : Oxford University Press. - 1741-0126 .- 1741-0134. ; 22:7, s. 413-420
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Tidskriftsartikel (refereegranskat)abstract
- We herein report the first directed evolution of Candida antarctica lipase A (CalA), employing a combinatorial active-site saturation test (CAST). Wild-type CalA has a modest E-value of 5.1 in kinetic resolution of 4-nitrophenyl 2-methylheptanoate. Enzyme variants were expressed in Pichia pastoris by using the episomal vector pBGP1 which allowed efficient secretory expression of the lipase. Iterative rounds of CASTing yielded variants with good selectivity toward both the (S)- and the (R)-enantiomer. The best obtained enzyme variants had E-values of 52 (S) and 27 (R).
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| 16. |
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