Search results for "RATES"

Rapid hyperpolarization and purification of the metabolite fumarate in aqueous solution

2020

Significance Magnetic resonance imaging is hindered by inherently low sensitivity, which limits the method for the most part to observing water molecules in the body. Hyperpolarized molecules exhibit strongly enhanced MRI signals which opens the door for imaging low-concentration species in vivo. Biomolecules can be hyperpolarized and injected into a patient allowing for metabolism to be tracked in real time, greatly expanding the information available to the radiologist. Parahydrogen-induced polarization (PHIP) is a hyperpolarization method renowned for its low cost and accessibility, but is generally limited by low polarization levels, modest molecular concentrations, and contamination by…

Selection on Coding Regions Determined Hox7 Genes Evolution

2003

The important role of Hox genes in determining the regionalization of the body plan of the vertebrates makes them invaluable candidates for evolutionary analyses regarding functional and morphological innovation. Gene duplication and gene loss led to a variable number of Hox genes in different vertebrate lineages. The evolutionary forces determining the conservation or loss of Hox genes are poorly understood. In this study, we show that variable selective pressures acted on Hox7 genes in different evolutionary lineages, with episodes of positive selection occurring after gene duplications. Tests for functional divergence in paralogs detected significant differentiation in a region known to …

The use of trypsin to solubilize wall proteins from Candida albicans led to the identification of chitinase 2 as an enzyme covalently linked to the y…

2002

The use of trypsin to break proteins covalently linked to the yeast walls of Candida albicans released approx. 50% of the proteins, but also glucose and N-acetylglucosamine. Analysis by affinity chromatography indicated that glucose and/or N-acetylglucosamine formed part of the same supramolecular complexes with mannoproteins. These complexes would represent a new type of cell wall structuration in which beta-1,6 glucan and chitin are linked to proteins. An internal peptide from a 50-kDa protein released by trypsin was sequenced, showing 100% identity with chitinase 2 protein and 92% with chitinase 3. The electrophoretic mobility of the chitinase 2 protein was changed by treatment with Endo…

A Na+-coupled C4-dicarboxylate transporter (Asuc_0304) and aerobic growth of Actinobacillus succinogenes on C4-dicarboxylates

2014

Actinobacillus succinogenes, which is known to produce large amounts of succinate during fermentation of hexoses, was able to grow on C4-dicarboxylates such as fumarate under aerobic and anaerobic conditions. Anaerobic growth on fumarate was stimulated by glycerol and the major product was succinate, indicating the involvement of fumarate respiration similar to succinate production from glucose. The aerobic growth on C4-dicarboxylates and the transport proteins involved were studied. Fumarate was oxidized to acetate. The genome of A. succinogenes encodes six proteins with similarity to secondary C4-dicarboxylate transporters, including transporters of the Dcu (C4-dicarboxylate uptake), Dcu…

Study of aromatic nucleophilic substitution with amines on nitrothiophenes in room-temperature ionic liquids: are the different effects on the behavi…

2006

The kinetics of the nucleophilic aromatic substitution of some 2-L-5-nitrothiophenes (para-like isomers) with three different amines (pyrrolidine, piperidine, and morpholine) were studied in three room-temperature ionic liquids ([bmim][BF4], [bmim][PF6], and [bm(2)im][BF4], where bmim = 1-butyl-3-methylimidazolium and bm(2)im = 1-butyl-2,3-dimethylimidazolium). To calculate thermodynamic parameters, a useful instrument to gain information concerning reagent-solvent interactions, the reaction was carried out over the temperature range 293-313 K. The reaction occurs faster in ionic liquids than in conventional solvents (methanol, benzene), a dependence of rate constants on amine concentration…

Carbohydrate Scaffolds for Combinatorial Syntheses That Allow Selective Deprotection of All Four Positions Independent of the Sequence

2004

Molecular simulation of mixed gas hydrates in astrophysical conditions

2020

In this PhD work, numerical simulation methods have been used in order to model clathrate hydrates at the molecular scale, in thermodynamic conditions typical of astrophysical contexts. The aim was to characterize the trapping abilities of those peculiar structures of water, by means of the tools used in adsorption studies. The results presented in the present thesis are focused on a couple of chemical species which are found to be abundant in our astrophysical vicinity and are quite similar: carbon monoxide, CO, and nitrogen, N2. Thus, the single-component clathrates of CO and N2, and the mixed hydrate CO-N2 have been studied, mainly using grand canonical Monte Carlo simulations. First, th…

New Biologically Active Triterpene-Saponins fromRandia dumetorum

1990

Two new triterpene-saponins, 3-O-[O-beta-D-glucopyranosyl-(1----4)-O-beta-D-glucopyranosyl-(1----3)-( beta- D-glucuronopyranosyl)]oleanolic acid (1), 3-O-[O-beta-D-glucopyranosyl-(1----6)-O-beta-D-glucopyranosyl- (1----3)-(beta-D-glucuronopyranosyl)]oleanolic acid (2) together with five known saponins (3-7) were isolated from the methanolic extract of the fruits of Randia dumetorum (Retz) Lam. (Rubiaceae). Their structures were established on the basis of chemical and spectral data. The compounds 1, 3, 4, 5 were found to enhance significantly the proliferation of human lymphocytes in vitro. The crude saponin fraction showed haemolytic, molluscicidal, and immunostimulating activities.

Réformes évolutionnistes du système des paiements internationaux : la création de systèmes des paiements supranationaux, une nécessité au regard des …

2012

At the height of the crisis, the international monetary system is powerless to reduce theinstability of exchange rates, the imbalance of the current account of balance ofpayments, instability of exchange rates and the development of speculation in financialmarkets the and the asymmetry between net exporters countries and net deficits countries.This thesis, which had the merit of opening new tracks in order to understand thecomplex relationships between global imbalances and the actual system, showed thatthese global imbalances are intrinsically linked to the failures of the internationalmonetary structure. To stop the deterioration of global imbalances, we propose that thesystem turns towar…

Lactaturia and loss of sodium-dependent lactate uptake in the colon of SLC5A8-deficient mice.

2008

SLC5A8 is a member of the sodium/glucose cotransporter family. It has been proposed that SLC5A8 might act as an apical iodide transporter in the thyroid follicular cells or as a transporter of short chain monocarboxylates. We have directly addressed the functional role of SLC5A8 in vivo by generation of SLC5A8 mutant mice. We found that SLC5A8 is responsible for the re-absorption of lactate at the apical membrane of the kidney proximal tubules and of serous salivary gland ducts. In addition, SLC5A8 mediated the uptake of lactate into colonocytes under physiological conditions. We did not find any evidence of SLC5A8 being essential for the apical iodide transport in the thyroid gland, even i…