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See detailFunction of Penicillin-binding protein 3 in Streptococcus Faecium
Coyette, Jacques; Somzé, Anne; Briquet, Jean-Jacques et al

in Hakenbeck, Regine; Höltje, Joachim-Volker; Labischinski, Harald (Eds.) The Target Penicillin : the Murein Sacculus of Bacterial Cell Walls Architecture and Growth : Proceedings (1983)

Cefotaxime at concns. around the min. inhibitory concn. (MIC, 5 μM) or below (0.1-1.0 μM) causes transformation of the normal S. faecium cells to bacilliform cells whose length increases with increasing ... [more ▼]

Cefotaxime at concns. around the min. inhibitory concn. (MIC, 5 μM) or below (0.1-1.0 μM) causes transformation of the normal S. faecium cells to bacilliform cells whose length increases with increasing duration of treatment. Septa are initiated but never reach completion. Affinity detn. for cefotaxime binding showed that the antibiotic binds preferentially to the 3 highest mol. wt. penicillin-binding proteins (PBP); PBP-2 and PBP-3 are about 100-fold more sensitive to cefotaxime than PBP-1. It appears, therefore, that PbP-2 and PBP-3 are involved in cell septation. This was confirmed by using cefatoxime in subinhibitory concns. (1 μM). From cell samples collected 30 and 60 min after addn. of cefotaxime, membranes were isolated, labeled with satg. [3H]benzylpenicillin and examd. by fluorog. Under these conditions only PBP-2 and PBP-3 were satd. by cefotaxime. At this stage no distinction could be made between the 2 proteins; either both or 1 of them may be involved in cell division. Cefoxitin produced morphol. alteration of a different nature than cefotaxime. The cefoxitin-treated cells had increased diam. and were slightly elongated. The most striking alteration was the frequent presence of conical poles contrasting with round poles obsd. in control cells. The morphol. alteration obsd. in cefoxitin-treated cells could be attributed to the inhibition of the function of PBP-1, PBP-2, or PBP-3. Elongated cells similar to those obtained with cefotaxime were not found with cefoxitin at concns. sufficient to sat. PBP-2. The main difference between cefotaxime- and cefoxitin-treated cells is that PBP-3 is satd. by cefotaxime but not altered at all by cefoxitin. Thus, septation inhibition must be due to the interaction of cefotaxime with PBP-3 [less ▲]

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See detailFunction of the Chloroplast Hydrogenase in the Microalga Chlamydomonas: The Role of Hydrogenase and State Transitions during Photosynthetic Activation in Anaerobiosis
Ghysels, Bart ULg; Godaux, Damien ULg; Matagne, René-Fernand ULg et al

in PLoS ONE (2013), 8(5), 64161

Like a majority of photosynthetic microorganisms, the green unicellular alga Chlamydomonas reinhardtii may encounter O2 deprived conditions on a regular basis. In response to anaerobiosis or in a ... [more ▼]

Like a majority of photosynthetic microorganisms, the green unicellular alga Chlamydomonas reinhardtii may encounter O2 deprived conditions on a regular basis. In response to anaerobiosis or in a respiration defective context, the photosynthetic electron transport chain of Chlamydomonas is remodeled by a state transition process to a conformation that favours the photoproduction of ATP at the expense of reductant synthesis. In some unicellular green algae including Chlamydomonas, anoxia also triggers the induction of a chloroplast-located, oxygen sensitive hydrogenase, which accepts electrons from reduced ferredoxin to convert protons into molecular hydrogen. Although microalgal hydrogen evolution has received much interest for its biotechnological potential, its physiological role remains unclear. By using specific Chlamydomonas mutants, we demonstrate that the state transition ability and the hydrogenase function are both critical for induction of photosynthesis in anoxia. These two processes are thus important for survival of the cells when they are transiently placed in an anaerobic environment. [less ▲]

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See detailFunction of the chloroplastic hydrogenase in the microalga Chlamydomonas reinhardtii: A trvel from dark to light
Godaux, Damien ULg

Doctoral thesis (2014)

The decreasing availability of fossil energy stocks and the eventuality of tragic climate changes caused by greenhouse gases lead to search for alternative renewable energy sources. Biological hydrogen ... [more ▼]

The decreasing availability of fossil energy stocks and the eventuality of tragic climate changes caused by greenhouse gases lead to search for alternative renewable energy sources. Biological hydrogen might be one promising renewable energy carrier. A specific and restricted group of microalgae developed the ability to produce hydrogen based on an oxygen-sensitive hydrogenase enzyme coupled to the photosynthetic pathway, acting as a putative valve for excess electrons in conditions where other electron acceptors are scarce. The unicellular green alga Chlamydomonas reinhardtii is widely regarded as a model organism for various biological processes, especially for photosynthesis. Moreover, the capacity of Chlamydomonas hydrogenase is claimed as the highest recorded in literature. Less than twenty years ago, a group of American scientists designed a new approach for sustained photobiological production of hydrogen, based on a two-stage protocol that temporally separates photosynthetic O2 evolution from the H2 production phase (Melis et al., 2000). The transition occurs upon sulfur deprivation of the culture and leads to an operating continuous production for several days, opening new possibilities in the aim of an economically rentable bioproduction. For these reasons, hydrogen photoproduction in Chlamydomonas reinhardtii has been extensively examined in the last decade as extension of photosynthesis research entailing the understanding of hydrogen metabolism in microalgae (for reviews, see Hankamer et al., 2007; Ghirardi et al., 2009; Ghysels and Franck, 2010). Despite the attractive trait of generating a renewable fuel from nature’s most plentiful resources, i.e. light and water, the physiological significance of such oxygen-sensitive enzyme coupled to oxygenic photosynthesis has been poorly investigated with the exception of some old studies (Kessler, 1973; Schreiber and Vidaver, 1974). In this work, hydrogenase implication in photosynthetic reactivation from dark and anoxic environment is investigated. In the first part of the work, by analyzing several strains affected in hydrogen metabolism (e.g. nda2-RNAi (Jans et al., 2008), pfl1 (Philipps et al., 2011), dum11 (Dorthu et al., 1992)), we show that the PSII–dependent photosynthetic electron flow upon dark to light shift is linearly related to the activity of hydrogenase, both for short and long-terms adaptation (Publication I). In agreement with this conclusion, a hydrogenase-deficient strain for the HydEF maturation factor (hydef, Posewitz et al., 2004) shows peculiar chlorophyll fluorescence induction kinetics after adaptation to dark and anoxia. Based on these findings, a novel imaging screening method is developed, allowing rapid identification of strains impaired in hydrogen metabolism. Compared to existing screens (for review, see Hemschemeier et al., 2009), our protocol is remarkably fast, sensitive and non-invasive. At this stage, application of this new screening method allowed us to isolate several hydrogenase-deficient strains, among which one was impaired for the hydrogenase maturation protein HydG (hydg-2 mutant). Chlamydomonas reinhardtii might frequently encounter period of dark and anoxia in its natural habitat, especially during the night when the microbial community respires the available oxygen. In the second part of my work, the physiological importance of hydrogenase is investigated in the context of photosynthesis induction at the onset of light upon anoxia. In such conditions, the plastoquinone pool is known as being overreduced. This triggers the process of state transitions which is described as allowing the redistribution of light capture between both photosystems to manage the redox poise of the photosynthetic pathway (for review, see Lemeille and Rochaix, 2010). We therefore revisit the impact of both state transitions and hydrogenase activity on the reactivation of photosynthetic electron flow (Publication II). Here we show that, in presence of hydrogenase, photosynthesis reactivation is slightly faster in stt7 mutant locked in state 1 (Depege et al., 2003) compared to wild type which is in state 2. However, photosynthesis reactivation is delayed in hydef stt7-9 double mutant compared to hydef mutant. This indicates that, in a hydrogenase-deficient context, state 2 promotes photosynthesis reactivation. Considered for a long time as being tightly interconnected (Finazzi et al., 1999; Finazzi et al., 2002; Finazzi and Forti, 2004), state transitions and PSI-CEF have recently been revealed as unrelated to each other (Takahashi et al., 2013). Nonetheless, the increasing of PSI antenna size in state 2 could even though enhance the PSI-CEF rate, in an indirect way, by enhancing PSI energy capture (Cardol et al., 2009; Alric, 2014). This reasonably raises the question of a possible involvement of PSI-CEF in photosynthesis induction. This possibility is further studied in the third and last part of the work. Thanks to mutants devoid of PSI-CEF (i.e. pgrl1 mutant (Tolleter et al., 2011)) and hydrogenase activity (i.e. hydg-2 mutant (Publication I)), we investigate the role played by PSI-CEF along with hydrogenase during photosynthesis reactivation during a shift from dark anoxia to light (Publication III). Herein, we demonstrate that Calvin cycle reactivation is proton gradient-dependent, most likely due to ATP requirement for carbon dioxide fixation. By measuring the PSI/PSII efficiency ratio during the re- illumination period, we point out the physiological occurrence of PSI-CEF within the first minutes of ilumination. We therefore propose a schematic model that assesses the electron flow through hydrogenase, PSI-CEF and Calvin cycle in function of the illumination period in all studied strains. Although lack of PSI-CEF does not appear to be essential for cell survival, photosynthesis reactivation is delayed in pgrl1 mutants. We also isolate a pgrl1 hydg-2 double mutant and demonstrate that the combination of both defects prevents any photosynthetic activity and strongly impairs growth. This highlights the importance for algae to keep both pathways in the course of evolution, being critical for the survival of Chlamydomonas reinhardtii in its natural environment. [less ▲]

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See detailFunction of the chloroplastic NAD(P)H dehydrogenase Nda2 for H(2) photoproduction in sulphur-deprived Chlamydomonas reinhardtii.
Mignolet, Emmanuel; Lecler, Renaud; Ghysels, Bart ULg et al

in Journal of biotechnology (2012), 162(1), 81-8

The relative contributions of the PSII-dependent and Nda2-dependent pathways for H(2) photoproduction were investigated in the green microalga Chlamydomonas reinhardtii after suphur-deprivation. For this ... [more ▼]

The relative contributions of the PSII-dependent and Nda2-dependent pathways for H(2) photoproduction were investigated in the green microalga Chlamydomonas reinhardtii after suphur-deprivation. For this purpose, H(2) gas production was compared for wild-type and Nda2-deficient cells with or without DCMU (a PSII-inhibitor) in the same experimental conditions. Nda2-deficiency caused a 30% decrease of the maximal H(2) photoevolution rate observed shortly after the establishment of anoxia, and an acceleration of the decline of H(2) photoevolution rate with time. DCMU addition to Nda2-deficient cells completely inhibited H(2) photoproduction, showing that the PSII-independent H(2) photoproduction relies on the presence of Nda2, which feeds the photosynthetic electron transport chain with electrons derived from oxidative catabolism. Nda2-protein abundance increased as a result of sulphur deprivation and further during the H(2) photoproduction process, resulting in high rates of non-photochemical plastoquinone reduction in control cells. Nda2-deficiency had no significant effect on photosynthetic and respiratory capacities in sulphur-deprived cells, but caused changes in the cell energetic status (ATP and NADPH/NADP+ ratio). The rapid decline of H(2) photoevolution rate with time in Nda2-deficient cells revealed a more pronounced inhibition of H(2) photoproduction by accumulated H(2) in the absence of non-photochemical plastoquinone reduction. Nda2 is therefore important for linking H(2) photoproduction with catabolism of storage carbon compounds, and seems also involved in regulating the redox poise of the photosynthetic electron transport chain during H(2) photoproduction. [less ▲]

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See detailFunction of the chloroplastic NADP(H) dehydrogenase NDA2 for the H2 photoproduction in sulphur-deprived Chlamydomonas reinhardtii
Mignolet, Emmanuel ULg; Lecler, Renaud ULg; Ghysels, Bart ULg et al

in Journal of Biotechnology (2012), 162

The relative contributions of the PSII-dependent and Nda2-dependent pathways for H2 photoproduction were investigated in the green microalga Chlamydomonas reinhardtii after suphur-deprivation. For this ... [more ▼]

The relative contributions of the PSII-dependent and Nda2-dependent pathways for H2 photoproduction were investigated in the green microalga Chlamydomonas reinhardtii after suphur-deprivation. For this purpose, H2 gas production was compared for wild-type and Nda2-deficient cells with or without DCMU (a PSII-inhibitor) in the same experimental conditions. Nda2-deficiency caused a 30 % decrease of the maximal H2 photoevolution rate observed shortly after the establishment of anoxia, and an acceleration of the decline of H2 photoevolution rate with time. DCMU addition to Nda2-deficient cells completely inhibited H2 photoproduction, showing that the PSII-independent H2 photoproduction relies on the presence of Nda2, which feeds the photosynthetic electron transport chain with electrons derived from oxidative catabolism. Nda2-protein abundance increased as a result of sulphur deprivation and further during the H2 photoproduction process, resulting in high rates of non-photochemical plastoquinone reduction in control cells. Nda2-deficiency had no significant effect on photosynthetic and respiratory capacities in sulphur-deprived cells, but caused changes in the cell energetic status (ATP and NADPH/NADP+ ratio). The rapid decline of H2 photoevolution rate with time in Nda2-deficient cells revealed a more pronounced inhibition of H2 photoproduction by accumulated H2 in the absence of non-photochemical plastoquinone reduction. Nda2 is therefore important for linking H2 photoproduction with catabolism of storage carbon compounds, and seems also involved in regulating the redox poise of the photosynthetic electron transport chain during H2 photoproduction. [less ▲]

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See detailThe function of the transcription factor Egr1 in zebrafish cartilage development
Dalcq, Julia ULg; Pasque, Vincent; Ramos, Sonia Davila et al

in Developmental Biology (2007, June 01), 306(1), 439-440

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See detailFunction, diversity and therapeutic potential of the N-terminal domain of human chemokine receptors
Szpakowska, Martyna ULg; Fievez, Virginie; Arumugan, Karthik et al

in Biochemical Pharmacology (2012)

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See detailFunction-based Analyses of Bacterial Symbionts Associated with the Brown Alga Ascophyllum nodosum and Identification of Novel Bacterial Hydrolytic Enzyme Genes
Martin, Marjolaine ULg

Doctoral thesis (2016)

Marine macroalgae are highly colonized by microorganisms, with which they maintain a close relationship characterized by both beneficial and detrimental interactions. Alga-associated bacteria have notably ... [more ▼]

Marine macroalgae are highly colonized by microorganisms, with which they maintain a close relationship characterized by both beneficial and detrimental interactions. Alga-associated bacteria have notably developed a range of enzymes enabling them to colonize the host surface and to use algal biomass as a carbon source. The hydrolytic potential of these bacteria, however, has been investigated almost solely at individual scale. Studies have shown the ability of some seaweed-associated bacterial strains to hydrolyze lipids, algal-cell-wall polysaccharides, and other sugars. In this work we aimed to investigate the hydrolytic potential of the bacterial microbiota associated with the brown alga Ascophyllum nodosum. For this we employed two complementary function-based approaches: functional metagenomics applied to this microbiota and functional analysis of the cultivable fraction thereof. By functional metagenomics, we identified numerous esterase genes, a beta-glucosidase gene, and an endocellulase gene. The cellulase was purified and biochemically characterized, showing interesting biotechnological features such as halotolerance and activity at low temperature. Furthermore, we assigned tentative origins to the identified genes, thus getting a glimpse of the bacterial taxa associated with the studied alga. Secondly, we investigated the cultivable surface microbiota associated with three A. nodosum samples. More than 300 bacteria were isolated, assigned to a bacterial taxon and screened for algal-polysaccharide-degrading enzymes (agarase, iota-carrageenase, kappa-carrageenase, and alginate lyases). This allowed the identification of several polysaccharolytic isolates, some of them likely to be new strains or novel species, belonging to two classes: the Flavobacteriia and the Gammaproteobacteria. Subsequently, we constructed and screened two plurigenomic libraries, each produced with the genomes of five representative isolates of each class, and identified several functional genes. With this work we highlight the presence of A. nodosum-associated bacterial taxa likely to entertain a privileged relation with seaweeds and having developed a range of hydrolytic activities assumed to enable them to associate with algae. We also provide information (taxa, abundances, genomic potential) on macroalgal-polysaccharide-degrading bacteria, in which interest has grown over the last ten years. [less ▲]

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See detailFunctional adaptations of the bacterial chaperone trigger factor to extreme environmental temperatures
Godin, Amandine ULg; Schmidpeter, P.; Schmid, F.X. et al

Poster (2014)

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See detailFunctional adaptations of the bacterial chaperone trigger factor to extreme environmental temperatures
Godin-Roulling, Amandine ULg; Schmidpeter, P.A.M.; Schmid, F.X. et al

in Environmental Microbiology (2015), 17(7), 2407-2420

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See detailFunctional Alterations in Order Short-Term Memory Networks in Adults With Dyslexia
Martinez Perez, Trecy ULg; Poncelet, Martine ULg; Salmon, Eric ULg et al

in Developmental Neuropsychology (2015), 40(7-8), 407-429

Dyslexia is characterized not only by reading impairment but also by short-term memory (STM) deficits, and this particularly for the retention of serial order information. Here, we explored the functional ... [more ▼]

Dyslexia is characterized not only by reading impairment but also by short-term memory (STM) deficits, and this particularly for the retention of serial order information. Here, we explored the functional neural correlates associated with serial order STM performance of adults with dyslexia for verbal and visual STM tasks. Relative to a group of age-matched controls, the dyslexic group showed abnormal activation in a network associated with order STM encompassing the right intraparietal and superior frontal sulcus, and this for both verbal and visual order STM conditions. This study highlights long-lasting alterations in non-language neural substrates and processes in dyslexia. [less ▲]

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See detailFunctional amphiphilic and biodegradable copolymers for intravenous vectorization
Van Butsele, Kathy ULg; Jérôme, Robert ULg; Jérôme, Christine ULg

in Polymer (2007), 48

This paper aims at reporting on the design of polymeric drug nanocarriers used in cancer therapy, with a special emphasis on the control of their biodistribution. First, the prominent role of poly ... [more ▼]

This paper aims at reporting on the design of polymeric drug nanocarriers used in cancer therapy, with a special emphasis on the control of their biodistribution. First, the prominent role of poly(ethylene oxide) in the lifetime of nanocarriers circulating in the blood stream is highlighted, and the origin of a passive targeting based on a difference in the anatomy of tumors and normal tissues is discussed. The main body of the review is devoted to the targeting of nanocarriers towards tumors and the underlying concepts. As a rule, either the constitutive polymer is stimuli-responsive and the locus of drug release is where the stimulation occurs, or a ligand endowed with specific recognition is grafted onto the nanocarrier. Finally, the fate of the nanocarrier after drug delivery and the bioelimination of the polymer(s) involved are briefly considered. [less ▲]

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See detailFunctional amphiphilic and degradable copolymers for drug delivery systems
Freichels, Hélène ULg; Pourcelle, Vincent; Plapied, Laurence et al

Poster (2008, December 18)

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See detailFunctional Analysis and the Finite Element Method
Stainier, Laurent; Tossings, Patricia ULg

Learning material (2008)

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See detailFunctional analysis of an FLC-LIKE gene in root chicory
Périlleux, Claire ULg; Pieltain, Alexandra ULg; D'Aloia, Maria ULg et al

in Comparative Biochemistry and Physiology. Part A, Physiology (2009), 153A(2/Suppl.), 198-199

Vernalization is known to promote flowering in Arabidopsis thaliana by inhibiting the expression of a strong repressor: FLOWERING LOCUS C (FLC). The recent cloning of an FLC-LIKE gene in sugar beet (Beta ... [more ▼]

Vernalization is known to promote flowering in Arabidopsis thaliana by inhibiting the expression of a strong repressor: FLOWERING LOCUS C (FLC). The recent cloning of an FLC-LIKE gene in sugar beet (Beta vulgaris; BvFL1) and – here – in root chicory (Cichorium intybus; CiFL1) suggests the conservation of FLC biological function during evolution of eudicots. Hence physiological questions that remain difficult to address in Arabidopsis can be studied in other species. We investigated the correlation between CiFL1 expression and plant-age dependent responsiveness to vernalization. We also studied the effect of post-vernalization growing temperature, which can stabilize or erase the vernalized state. [less ▲]

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See detailFunctional analysis of dual-specificity protein phosphatases in angiogenesis
Amand, Mathieu; ERPICUM, Charlotte ULg; Gilles, Christine ULg et al

in Pulido, Rafael (Ed.) Protein Tyrosine Phosphatases: Methods and Protocols (2016)

Therapeutic perspectives targeting angiogenesis in cancer stimulated an intense investigation of the mechanisms triggering and governing angiogenic processes. Several publications have highlighted the ... [more ▼]

Therapeutic perspectives targeting angiogenesis in cancer stimulated an intense investigation of the mechanisms triggering and governing angiogenic processes. Several publications have highlighted the importance of typical dual-specificity phosphatases (DSPs) or MKPs in endothelial cells and their role in controlling different biological functions implicated in angiogenesis such as migration, proliferation, apoptosis, tubulogenesis and cell adhesion. However, among atypical DSPs, the only one investigated in angiogenesis was DUSP3. We recently identified this DSP as new key player in endothelial cells and angiogenesis. In this chapter we provide with detailed protocols and models used to investigate the role of DUSP3 in endothelial cells and angiogenesis. We start the chapter with an overview of the role of several DSPs in angiogenesis. We continue with providing a full description of a highly efficient transfection protocol to deplete DUSP3 using small interfering RNA (siRNA) in the primary Human Umbilical Vein Endothelial Cells (HUVEC). We next describe the major assays used to investigate different processes involved in angiogenesis such as tube formation assay, proliferation assay and spheroids sprouting assay. We finish the chapter by validating our results in DUSP3-knockout mice using in vivo angiogenesis assays such as Matrigel plug and Lewis lung carcinoma cell subcutaneous xenograft model followed by anti-CD31 immunofluorescence and ex vivo aortic ring assay. All methods described can be adapted to other phosphatases and signaling molecules. [less ▲]

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See detailFunctional analysis of FRD3 in Arabidopsis
Scheepers, Maxime ULg; Charlier, Jean-Benoit ULg; Spielmann, Julien ULg et al

Poster (2015, June)

Zinc and iron are two essential micronutrients for plants. The homeostasis networks of the two metals are intertwined. The FRD3 (FERRIC REDUCTASE DEFECTIVE 3) protein, a member of the MATE family of ... [more ▼]

Zinc and iron are two essential micronutrients for plants. The homeostasis networks of the two metals are intertwined. The FRD3 (FERRIC REDUCTASE DEFECTIVE 3) protein, a member of the MATE family of membrane transporters, is a citrate transporter involved in iron homeostasis and playing a role in zinc tolerance in Arabidopsis. The FRD3 gene displays a complex regulation. Alternative transcript initiation for FRD3 determines two transcripts, which differ in their 5'UTRs and have differential translation efficiency. The two transcripts are selectively regulated under stress conditions: iron and zinc depletion, zinc excess or cadmium presence. We are aiming to determine the FRD3 function in zinc and iron homeostasis in Arabidopsis. We will present data (i) on the functional characterization of the alternative transcripts and their role in metal homeostasis in Arabidopsis and (ii) on the zinc phenotypes of the frd3 mutant. [less ▲]

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