Clostridium perfringensepsilon toxin H149A mutant as a platform for receptor binding studies

Clostridium perfringens epsilon toxin (Etx) is a pore-forming toxin responsible for a severe and rapidly fatal enterotoxemia of ruminants. The toxin is classified as a category B bioterrorism agent by the U.S. Government Centres for Disease Control and Prevention (CDC), making work with recombinant toxin difficult. To reduce the hazard posed by work with recombinant Etx, we have used a variant of Etx that contains a H149A mutation (Etx-H149A), previously reported to have reduced, but not abolished, toxicity. The three-dimensional structure of H149A prototoxin shows that the H149A mutation in domain III does not affect organisation of the putative receptor binding loops in domain I of the toxin. Surface exposed tyrosine residues in domain I of Etx-H149A (Y16, Y20, Y29, Y30, Y36 and Y196) were mutated to alanine and mutants Y30A and Y196A showed significantly reduced binding to MDCK.2 cells relative to Etx-H149A that correlated with their reduced cytotoxic activity. Thus, our study confirms the role of surface exposed tyrosine residues in domain I of Etx in binding to MDCK cells and the suitability of Etx-H149A for further receptor binding studies. In contrast, binding of all of the tyrosine mutants to ACHN cells was similar to that of Etx-H149A, suggesting that Etx can recognise different cell surface receptors. In support of this, the crystal structure of Etx-H149A identified a glycan (β-octyl-glucoside) binding site in domain III of Etx-H149A, which may be a second receptor binding site. These findings have important implications for developing strategies designed to neutralise toxin activity

A Conceptual and Technological Framework for Building Collaborative Learning Environments

Non

In vitro selection of miltefosine resistance in promastigotes of Leishmania donovani from Nepal : genomic and metabolomic characterization

n this study, we followed the genomic, lipidomic and metabolomic changes associated with the selection of miltefosine (MIL) resistance in two clinically derived Leishmania donovani strains with different inherent resistance to antimonial drugs (antimony sensitive strain Sb-S; and antimony resistant Sb-R). MIL-R was easily induced in both strains using the promastigote-stage, but a significant increase in MIL-R in the intracellular amastigote compared to the corresponding wild-type did not occur until promastigotes had adapted to 12.2 μM MIL. A variety of common and strain-specific genetic changes were discovered in MIL-adapted parasites, including deletions at the LdMT transporter gene, single-base mutations and changes in somy. The most obvious lipid changes in MIL-R promastigotes occurred to phosphatidylcholines and lysophosphatidylcholines and results indicate that the Kennedy pathway is involved in MIL resistance. The inherent Sb resistance of the parasite had an impact on the changes that occurred in MIL-R parasites, with more genetic changes occurring in Sb-R compared with Sb-S parasites. Initial interpretation of the changes identified in this study does not support synergies with Sb-R in the mechanisms of MIL resistance, though this requires an enhanced understanding of the parasite's biochemical pathways and how they are genetically regulated to be verified fully

Interaction Analysis Supporting Participants' Selfregulation in a Generic CSCL System

International audienceInteraction analysis can provide information directly to learners and teachers in order to assess and self-regulate their ongoing activity. Omega+ is a generic CSCL system that uses explicit models as parameters for flexibly supporting different kinds of collaborative applications. This paper describes Omega+ model-based generic approach for supporting participants' selfregulation through interaction analysis. Some quantitative and qualitative results obtained with the proposed approach are discussed

Deixis in synchronous CSCL systems. A collection of socio-technical patterns.

International audienceThere is a growing interest in synchronous CSCL systems that combine a communication space with a task space for supporting knowledge building by distributed or co-located small groups of learners. In that context, in which collaborative learning processes are scattered above two distinct spaces, deictic references to the objects in both spaces, the time of learners' actions, and the identity of participants are very important. This paper describes a structured collection of high-level patterns whose purpose is to catalog and document design knowledge about the mechanisms, resources and practices for deictic referencing

Foaming, emulsifying and rheological properties of extracts from a co-product of the Quorn fermentation process

Julien Lonchamp - ORCID: 0000-0001-7954-4745 https://orcid.org/0000-0001-7954-4745Item also deposited in University of Edinburgh repository, available at: https://www.research.ed.ac.uk/portal/en/publications/foaming-emulsifying-and-rheological-properties-of-extracts-from-a-coproduct-of-the-quorn-fermentation-process(c1316b1e-0940-4329-8b28-f010f4156548).htmlThis study assessed the functional profile (foaming, emulsifying and rheological properties), proteomic and metabolomic composition of a naturally foaming and currently unexploited co-product (centrate) from the Quorn fermentation process. Due to the low environmental footprint of this process the centrate is a potential source of sustainable functional ingredients for the food industry. A range of fractions were isolated from the centrate via successive ultrafiltration steps. The retentate 100 (R100) fraction, which was obtained following a 100 kDa ultrafiltration, displayed good foaming, emulsifying and rheological properties. R100 solutions and oil-in-water emulsions displayed high viscosity, while R100 solutions and hydrogels showed high viscoelasticity. R100 foams displayed high stability while oil-in-water R100 emulsions showed small and stable oil droplet size distributions. Large mycelial aggregates were reported in R100 solutions and gels, correlating with their high viscosity and viscoelasticity. A dense mycelial network was observed in R100 foams and contributing to their stability. In parallel tensiometry measurements highlighted the presence of interfacially active molecules in R100 which formed a rigid film stabilising the oil/water interface. A number of functional metabolites and proteins were identified in the centrate, including a cerato-platanin protein, cell membrane constituents (phospholipids, sterols, glycosphingolipids, sphingomyelins), cell wall constituents (chitin, chitosan, proteins), guanine and guanine-based nucleosides and nucleotides. This study highlighted the potential of functional extracts from the Quorn fermentation process as novel ingredients for the preparation of sustainable food products and the complex and specific nature of the centrate’s functional profile, with contributions reported for both mycelial structures and interfacially active molecules.This work was supported by the Engineering and Physical Sciences Research Council (Grant number EP/J501682/1 Foaming and Fat Replacer Ingredients).https://doi.org/10.1007/s00217-019-03287-z245pubpu

Sonicated extracts from the Quorn fermentation co-product as oil-lowering emulsifiers and foaming agents

Replaced AM with VoR 2020-02-07This study assessed the impact of sonication on the structure and properties of a functional extract (retentate 100 or R100) from the Quorn fermentation co-product (centrate). In a previous study we reported that the R100 fraction displayed good foaming, emulsifying and rheological properties. Sonication of a R100 solution led to the breakdown of the large hyphal structures characteristic of this extract into smaller fragments. Foams prepared with sonicated R100 displayed a higher foaming ability than with untreated R100 and a high foam stability but lower than untreated R100 ones. Oil-in-water emulsions prepared with sonicated R100 displayed smaller oil droplet size distributions than with untreated R100. Confocal micrographs suggested that small fungal fragments contributed to the stabilisation of oil droplets. 50% oil-reduced R100 emulsions were prepared by mixing R100 emulsions (untreated or sonicated) with a sonicated R100 solution at a 1:1 ratio. Smaller oil droplet size distributions were reported for the oil-reduced emulsions. These results showed that the addition of small hyphal fragments or surface-active molecules and molecular aggregates released during sonication contributed to the formation and stabilisation of smaller oil droplets. This study highlighted the potential to modulate the structure, emulsifying and foaming properties of functional extracts from the Quorn fermentation co-product by sonication and the potential of these extracts as oil-lowering agents in emulsion-based products through the reduction of oil droplet size and their stabilisation.This work was supported by the Engineering and Physical Sciences Research Council [grant number EP/J501682/1 Foaming and Fat Replacer Ingredients].https://doi.org/10.1007/s00217-020-03443-w246pubpub

OE-4-1 Extraction and properties of protein extracted from fungal fermentations [abstract]

From Elsevier via Jisc Publications RouterHistory: issued 2025-03-25, epub 2025-07-07Article version: VoRPublication status: PublishedJulien Lonchamp - ORCID: 0000-0001-7954-4745 https://orcid.org/0000-0001-7954-4745pubpu

Functional fungal extracts from the Quorn fermentation co-product as novel partial egg white replacers

Replaced AM with VoR 2020-01-17The production of mycoprotein biomass by Marlow Foods for use in their meat alternative brand Quorn is a potential source of sustainable alternatives to functional ingredients of animal origin for the food industry. The conversion of this viscoelastic biomass into the Quorn meat-like texture relies on functional synergy with egg white (EW), effectively forming a fibre gel composite. In a previous study we reported that an extract (retentate 100 or R100) obtained from the Quorn fermentation co-product (centrate) via ultrafiltration displayed good foaming, emulsifying and rheological properties. This current study investigated if a possible similar synergy between EW and R100 could be exploited to partially replace EW as foaming and/or gelling ingredient. The large hyphal structures characteristic of R100 solutions were observed in EW-R100 mixtures, while EW-R100 gels showed dense networks of entangled hyphal aggregates and filaments. R100 foams prepared by frothing proved less stable than EW ones, however a 75/25 w/w EW-R100 mixture displayed a similar foam stability to EW. Simlarly R100 hydrogels proved less viscoelastic than EW ones, however the viscoelasticity of gels prepared with 50/50 w/w and 75/25 w/w EW-R100 proved similar to those of EW gels while 75/25 w/w EW-R100 gels displayed similar hardness to EW ones. Both results highlighted a functional synergy between the R100 material and EW proteins. In parallel tensiometry measurements highlighted the presence of surface-active material in EW-R100 mixtures contributing to their high foaming properties. These results highlighted the potential of functional extracts from the Quorn fermentation process for partial EW replacement as foaming and gelling agent, and the complex nature of the functional profile of EW-R100 mixtures, with contributions reported for both hyphal structures and surface-active material.This work was supported by the Engineering and Physical Sciences Research Council [grant number EP/J501682/1 Foaming and Fat Replacer Ingredients].https://doi.org/10.1007/s00217-019-03390-1246pubpu