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Dimitri WEISS Institut d'Administration des Entreprises, Paris The Health Care Business. ... Fayol en fut, à sa façon, un précurseur, à l'époque peu compris et peu suivi. ...doi:10.7202/029079ar fatcat:lawov44k4ndyple6nddohzza5u
Giant lipid vesicles (GVs) are emerging models for investigating the properties and reactivity of cell-like microcompartments, providing useful information about plausible protocellular structures in primitive times, as well as for the modern synthetic biology goal of constructing the first artificial cell from its reconstituted and partly modified components. Here we explore a novel methodology of GV purification by microfiltration under reduced pressure, operated by a simple apparatus. Thedoi:10.1371/journal.pone.0192975 pmid:29451909 pmcid:PMC5815610 fatcat:eqwnh2i3lvfnjmslyocdqw2hju
more »... hod has been characterized in terms of flow rate, amount of lipid loss, quality of recovered GVs, and size distribution. A case study is reported to show the practicability of GV microfiltration. A clickable fluorescent probe was encapsulated inside GVs; more than 99.9% of the non-entrapped probe was easily and rapidly removed by multiple microfiltrations. This novel methodology is briefly discussed as a future tool for selection experiments on GV populations. Irrespective of the preparation method, the crude GV suspension will contain nonentrapped solute molecules. For many applications, the GVs need to be purified from nonentrapped solutes that might interfere in successive measurements or reactions. GVs are typically purified by dialysis or by differential centrifugation. Dialysis is time-consuming (several hours) and requires a large volume of external solution. In some applications, dialysis can be disadvantageous because the external solution can be expensive or difficult to prepare. Prolonged times also might be a drawback, especially if GVs contain sensitive molecules. Differential centrifugation is more rapid than dialysis (10-15 minutes), but it requires a density difference between the inner and the outer solutions, which is generally achieved by incorporating relatively high concentrations of sucrose inside GVs and glucose in the outer solution. The centrifuged GVs, when collected, might include part of their surrounding solution, impairing the purification, and more centrifugation rounds are thus required; this increases the overall purification time and reduces the number of recovered GVs. As part of our ongoing research on the production, manipulation and usage of GVs, we were interested in exploring alternative purification methods. Here we report the microfiltration of GVs by means of a thin nylon membrane with narrow pores (0.2 μm). When coupled to a dilution of the GV sample, this procedure allows for a very effective removal of non-entrapped solutes (> 99.9%), is faster than dialysis or centrifugation, does not require a density difference, and can be used for volume samples of for example 10 mL being diminished to ca. 500 μL; below this minimal volume it is difficult to finely control the filtration end point and/or recover the GV suspension from the filter. This method is very practical and useful, even if GV recovery is not very high, depending on conditions, between 10% and 60% after each filtration step. Interestingly, since the filter acts as a physical support for GVs, our approach can also be used for in situ repetitive GV manipulations, i.e., addition of first reactants to GVs over the filter, wash, filter, addition of second reactants, and so on. In this way, it becomes possible to investigate vesicle transformations, intra-vesicle or membrane-localized reactions, and design vesicle competition or selection experiments.
Although prebiotic condensations of glycerol, phosphate and fatty acids produce phospholipid esters with a racemic backbone, most experimental studies on vesicles intended as protocell models have been carried out by employing commercial enantiopure phospholipids. Current experimental research on realistic protocell models urgently requires racemic phospholipids and efficient synthetic routes for their production. Here we propose three synthetic pathways starting from glycerol or from racemicdoi:10.3390/sym12071108 fatcat:rjoj6mkypbe5zliwyvb5lmnbg4
more »... lketal (α,β-isopropylidene-dl-glycerol) for the gram-scale production (up to 4 g) of racemic phospholipid ester precursors. We describe and compare these synthetic pathways with literature data. Racemic phosphatidylcholines and phosphatidylethanolamines were obtained in good yields and high purity from 1,2-diacylglycerols. Racemic POPC (rac-POPC, (R,S)-1-palmitoyl-2-oleoyl-3-phosphocholine), was used as a model compound for the preparation of giant vesicles (GVs). Confocal laser scanning fluorescence microscopy was used to compare GVs prepared from enantiopure (R)-POPC), racemic POPC (rac-POPC) and a scalemic mixture (scal-POPC) of (R)-POPC enriched with rac-POPC. Vesicle morphology and size distribution were similar among the different (R)-POPC, rac-POPC and scal-POPC, while calcein entrapments in (R)-POPC and in scal-POPC were significantly distinct by about 10%.
., 2020; Fayolle et al., 2017; Fiore et al., 2017; Fiore and Buchet, 2020; Monnard and Deamer, 2003) . ...doi:10.1016/j.isci.2020.101677 pmid:33163935 pmcid:PMC7609504 fatcat:vwfnmvrrhjglbhzlnvszkt4rji
et al.. Crude phosphorylation mixtures containing racemic lipid amphiphiles self-assemble to give stable primitive compartments. It is an open question how the chemical structure of prebiotic vesicle-forming amphiphiles complexified to produce robust primitive compartments that could safely host foreign molecules. Previous work suggests that comparingly labile vesicles composed of plausibly prebiotic fatty acids were eventually chemically transformed with glycerol and a suitable phosphatedoi:10.1038/s41598-017-18053-y pmid:29273739 pmcid:PMC5741756 fatcat:comozlcmwzamtpsgeth63nmrpy
more »... into phospholipids that would form robust vesicles. Here we show that phosphatidic acid (PA) and phosphatidylethanolamine (PE) lipids can be obtained from racemic dioleoyl glycerol under plausibly prebiotic phosphorylation conditions. Upon in situ hydration of the crude phosphorylation mixtures only those that contained rac-DOPA (not rac-DOPE) generated stable giant vesicles that were capable of encapsulating watersoluble probes, as evidenced by confocal microscopy and flow cytometry. Chemical reaction sideproducts (identified by IR and MS and quantified by 1 H NMR) acted as co-surfactants and facilitated vesicle formation. To mimic the compositional variation of such primitive lipid mixtures, self-assembly of a combinatorial set of the above amphiphiles was tested, revealing that too high dioleoyl glycerol contents inhibited vesicle formation. We conclude that a decisive driving force for the gradual transition from unstable fatty acid vesicles to robust diacylglyceryl phosphate vesicles was to avoid the accumulation of unphosphorylated diacylglycerols in primitive vesicle membranes. The spontaneous supramolecular self-assembly of amphiphiles to give vesicles is a powerful thermodynamic drive for the emergence of primitive cell-like compartments on the early Earth 1-7 . Fatty acid vesicles are plausible models of primitive cells 8,9 but contemporary cell membranes are based on mixtures of phospholipids, glycolipids and proteins. This elicits the questions about the stepwise transition from very early achiral or racemic amphiphiles to enantiopure glycerophospholipids. It has been argued that the complexification and the compositional evolution of primitive membranes was subjected not only to chemical rules (which chemical transformation is possible?) but also to a sort of supramolecular selection based on the 'performance' of the resulting membranes and whole vesicles -e.g., low critical aggregation (micelle, vesicle) concentration, membrane permeability, capture and retention of non-lipidic organic molecules, membrane growth and vesicle division upon the addition of membrane components, vesicle stability at high magnesium and calcium ions concentrations 8, 9 . Although chemistry suggests several plausible pathways for the stepwise transformation of simple amphiphiles into complex lipids 10-15 , the experimental verifications of the existence, stability, and properties of vesicles composed of plausibly primitive amphiphile mixtures are still limited 9,16-21 . Here we report on primitive membrane systems that originate from crude lipid phosphorylation mixtures. Our starting point is a non-phosphorylated diacylglycerol racemate. Glycerol is a reduced formose C 3 reaction Published: xx xx xxxx OPEN www.nature.com/scientificreports/ 2 SciEnTific REPORTS | (2017) 7:18106 |
A series of alkyl thioglycosides and alkyl thiodiglycosides bearing glucose and N-acetylglucosamine residues were prepared by thiol-ene coupling in moderate to good yields (40-85%). Their binding ability towards wheat germ agglutinin was measured by competitive enzyme-linked lectin assays. One of the synthetic compounds presenting two GlcNAc units showed the highest inhibitory effect of this study with an IC50 of 11 µM corresponding to a 3182-fold improvement compared to GlcNAc. These syntheticdoi:10.3762/bjoc.15.90 pmid:31164930 pmcid:PMC6541351 fatcat:wfs5uawyzzempi7yi7pjqvvwia
more »... molecules were used to produce giant vesicles, alone or in mixture with phospholipids, mimicking bacterial outer membrane vesicles (OMV) with potential antiadhesive properties.
Quant à Dimitri UZUNIDIS, il estime que la nature systémique des relations qui caractérisent un milieu économique et social explique en effet ce qui favorise ou non l'acte d'innover. ... Olivier TOUT AIN et Alain FAYOLLE étudient la notion de compétence dans les pratiques d'accompagnement (qualifiées d'ingénierie combinatoire des ressources) des entrepreneurs. ...doi:10.3917/maorg.006.0011 fatcat:g2lidvibjzgtncbupfloalwcyy
Dimitri WEISS Institut d'Administration des Entreprises, Paris The Health Care Business. ... Fayol en fut, à sa façon, un précurseur, à l'époque peu compris et peu suivi. ...doi:10.7202/029080ar fatcat:5mr66bcwwfhp7cmwg3jdben7sq
Fassnacht, Fabian Fayolle, Adeline Felzer, Benjamin S. Fender, Ann-Catrin Fernandes, Paulo Fernandez-Diaz, Juan Fernando, Danilo D. ... Van der Zande, Dimitry Van Diepen, Linda Van Leeuwen, Eveline Van Leeuwen, Martin Van Oijen, Marcel Van Oosterzee, Penny Van Stan, John T. Vanhellemont, Margot Varanda, Carla M. R. ...doi:10.3390/f7010026 fatcat:m4p555bn4jawrl6j2a2scvu7ke
Alain VINET Université Laval Administration industrielle et générale, par Henri Fayol, édition présentée par P. Morin, Paris, Dunod, 1979, 156 pp. ... Dimitri WEISS Institut d'Administration des Entreprises, Paris Les nouvelles formes d'organisation du tra- vail, vol. 2, Genève, Bureau internatio- nal du travail, 1979, 161 pp. ...doi:10.7202/029078ar fatcat:aqc2pmrvrzdfdfdx3gsfjio26m
s'est traduite par l'arrivée de collègues venant d'autres spécialités de la gestion (Philippe Desbrières et Pierre-Jean Benghozi, par exemple), d'autres disciplines scientifiques (Sophie Boutillier et Dimitri ... Depuis sa création, en 2001, notre revue a connu plusieurs rédacteurs en chef, Bertrand Saporta, Robert Paturel, Alain Fayolle, et un directeur de publication unique, Thierry Verstraete qui s'est investi ...doi:10.3917/entre.091.0001 fatcat:2v2oanf53bcdfbpdmghhhgb6xa
Dimitri WEISS Institut d'Administration des Entreprises, Paris Mais là s'arrêtent les points communs. ... Alain VINET Université Laval Administration industrielle et générale, par Henri Fayol, édition présentée par P. Morin, Paris, Dunod, 1979, 156 pp. ...doi:10.7202/029077ar fatcat:i6y6ggbojrbbvkotjf2oznncsu
FRE/ENG 95100166 Endress, Gerhard (Ed) & 1992 Gutas, Dimitri | Kruk, Remke (Rev) 1994 A Greek and Arabic Lexicon: Materials for a Dictionary of the Mediaeval Translations from Greek into Arabic, Fascicle ... (Rev) Aphasia Therapy in Practice: Writing, Aphasiology, 1994, 8, 5, Sept-Oct, 505-506. 1994 95r00177 Fayol, M.., 1992 Gombert, J. E., Lecocq, P., Sprenger-Charolles, L. & Za L Bastien-Toniazzo, M M. ...
Tsitsiklis, John N. (1-MIT); Bertsekas, Dimitri P. (1-MIT) Distributed asynchronous optimal routing in data networks. IEEE Trans. Automat. Control 31 (1986), no. 4, 325-332. ... Wolfgang Feitscher (Berlin) 87¢:68007 68P Theory of data 87¢:6801 1 Fayolle, Guy (F-INRIA); 87¢:68008 Flajolet, Philippe (F-INRIA); Hofri, Micha (IL-TECH-C) On a functional equation arising in the analysis ...
To know more about the elaboration of a text, writing researchers have developed a variety of on-line research methods (Fayol 1997; Favart & Olive 2005). ... (4) Alors Dimitri poussa de toutes ses forces / et la grille s’arracha. ...doi:10.4000/cognitextes.992 fatcat:kfjsmh4va5gm5d236jsqfnjysu
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