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J Graille

Publications and source records attributed to J Graille.

8 recordsLinked to original sources
PubMed2003

Acyl migration incidence on accuracy of a triacylglycerol regioanalysis--a theoretical evaluation.

We will consider the Grignard chemical deacylation to study the regioanalysis of triacylglycerols (TAGs). Using a given TAG structure, a cross-contamination model is developed and used for evaluating the incidence of the acyl migration and its influence on the accuracy of a regiospecific analysis of the molecule. Despite unavoidable isomerization, the newly formed alpha,beta-diacylglycerols are considered as most representative of the original TAG composition. In this paper, we present evidence that in conditions of limited acyl migration, the regiospecific distribution could more accurately be determined from the alpha-monoacylglycerol rather than through calculations based on the alpha,beta-diacylglycerols fraction.

Acylation↗
PubMed2002

A direct method for regiospecific analysis of TAG using alpha-MAG.

An analytical procedure was developed for regiodistribution analysis of TAG using alpha-MAG prepared by an ethyl magnesium bromide deacylation. In the present communication, the deacylation procedure is shown to lead to representative alpha-MAG, allowing the composition of the native TAG in the alpha-position to be determined directly. The composition in the beta-position can then be estimated from the composition of the alpha-MAG and TAG according to the formula 3 x TAG - 2 x alpha-MAG. The estimates are superior to those obtained using the alpha,beta-DAG and Brockerhoff calculations as they come closer to the theoretical value and have smaller SD. The present procedure, first demonstrated on a synthetic TAG, was then successfully applied to the analysis of borage oil, milkfat, and tuna oil.

Acylation↗
PubMed1997

Chemoenzymatic synthesis of glucose fatty esters.

D-Glucose fatty esters at C-6 were obtained by chemoenzymatic synthesis involving 1,2-O-cyclohexylidene-alpha-D-glucofuranose (1) followed by hydrolysis of the cyclohexylidene protecting group. The enzymatic esterification of 1 was performed with fatty acids of variable chain lengths (C8:0 to C18:0). The kinetic of the reaction was studied for each fatty acid and the structure of the octanoyl ester was determined by 1H and 13C NMR spectroscopy.

Esters↗
PubMed1996

Determination of pregastric lipase specificity in young ruminants.

The combined hydrolysis of a chiral triglyceride clearly defined on these three positions and of its racemic equivalent reveals all sorts of lipase specificities: regioselectivity, typoselectivity and stereospecificity. This article describes a study of the pregastric lipases of young ruminants (kid, calf, lamb), whose specificity is still somewhat ambiguous. The use of a chiral triglyceride in which position sn 1 was occupied by a short-chain fatty acid showed that these lipases had dual specificity, i.e. a combination of typoselectivity with respect to short-chain fatty acids and sn3 stereospecificity. A comparison between the performance of the lipase of young animals and the fatty acid composition and distribution in the mother's milk suggests that the degree of dual specificity in these enzymes is related to the characteristics of the mother's milk.

Animals↗
PubMed1996

Measurement of free glycerol in biofuels.

A method has been developed to determine the free glycerol content in esters derived from vegetable oils. After extraction of glycerol, its measurement in small quantities in biofuels (methyl or ethyl esters) is possible by high-pressure liquid chromatography combined with pulsed amperometric detection, HPLC-PAD. The method has proved to be simple, rapid and accurate. The limit of detection is 1 microg/g.

Journal Article↗
PubMed1994

Interactions between beta-cyclodextrin and insoluble glyceride monomolecular films at the argon/water interface: application to lipase kinetics.

A study of the desorption rate of insoluble monomolecular films of oleic acid (OA), monoolein (MO), 1,2-diolein (1,2-DO), 1,3-diolein (1,3-DO) and triolein (TO) at the argon/water interface by water-soluble beta-cyclodextrin (beta-CD) is reported. The desorption of OA and MO involves probably the complexation of the single acyl chain with beta-CD and sequestering of the formed soluble OA/beta-CD and MO/beta-CD complexes from the argon/water interface. In the case of monolayers of multiple acyl chain molecules such as DO and TO, no detectable change in the surface pressure occurred after beta-CD injection. The surface rheological dilatational properties of the monolayers of DO and TO in the presence of beta-CD in the subphase were studied. The elasticity of the DO monolayer remained unchanged, whereas the decrease in the surface elasticity of the TO film was attributed to the formation of a water-insoluble TO/beta-CD complex. With the 'tuning fork' model, one acyl chain of TO can be included in the beta-CD cavity. The formed TO/beta-CD complex present at the interface retarded the propagation of the dilatational deformation along the plane of the monolayer. Schematic models have been proposed in an attempt to explain the different complexation of these lipids by beta-CD at the argon/water interface. In addition to the above results, the presence of beta-CD in the water subphase makes it possible for the first time to perform kinetic measurements of the lipase hydrolysis rates of long-chain glycerides forming monomolecular films.

Argon↗
PubMed1987

An improved method for the colorimetric assay of lipase activity using an optically clear medium.

Lipase activity can be spectrophometrically measured in an optically clear medium using long chain fatty thioesters of 1-mercapto-2,3-propanediol or 2-mercaptoethanol as substrates. With hexamethylphosphoric triamide solutions of these thiosubstrates, the Michaëlis-Menten constants of lipase from Rhizopus arrhizus were determined. The effects of calcium chloride and of bovine serum albumin on the enzyme activity were established.

Colorimetry↗