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J F Thibault

Publications and source records attributed to J F Thibault.

23 records · Page 2Linked to original sources
PubMed1992

Influence of the degree of polymerization of oligogalacturonates and of esterification pattern of pectin on their recognition by monoclonal antibodies.

The ability of galacturonic and oligogalacturonic acids with degrees of polymerization (DP) from 2 to 10 to inhibit the recognition of homopolygalacturonic acid by a monoclonal antibody specific for dimers of pectin (F Liners, J-J Letesson, C Didembourg, P Van Cutsem [1989] Plant Physiol 91: 1419-1424) has been tested by enzyme-linked immunosorbent assays. Oligomers of DP9 and above preincubated with the antibodies clearly inhibited the association between the antibodies and immobilized pectin. A minimum DP of nine consecutive galacturonic residues is thus necessary to be associated through calcium cations to form dimers. Randomly deesterified pectin was recognized by the antibody if its degree of methylesterification was <30%, whereas blockwise deesterified pectin was recognized up to 40% of methylesterification. The replacement of calcium ions by magnesium prevented the recognition of polygalacturonic acid by the antibody.

Journal Article↗
PubMed1991

Influence of the substituents of the carboxyl groups and of the rhamnose content on the solution properties and flexibility of pectins.

Viscometric measurements were carried out on well-characterized apple, citrus, sugar-beet pectins in order to analyse the effect of the nature and the amount of substituents (methyl, amide, acetyl groups) and of the rhamnose content on the flexibility of the polymeric backbone. Through the dependence of the intrinsic viscosity with the ionic strength the flexibility parameter B was determined. B values between 0.072 and 0.017 indicate that pectins are relatively stiff molecules. However, an increase in flexibility is noticeable with the rise of the rhamnose content and of the amount of amide groups of the pectic acids. The flexibility is also sensitive to the degree of methylation.

Molecular Structure↗
PubMed1989

Structure of citrus pectins and viscometric study of their solution properties.

Citrus pectins with degrees of methylation between 30 and 72% were carefully characterized in order to determine their charge density and molecular weight distribution, the content in galacturonic acid and in neutral sugars, the degree of methylation and acetylation. Using enzymic degradation it has been found that pectin molecules consist mainly of long homogalacturonan regions with some regions of neutral sugars as side chains attached on rhamnose residues. The viscometric behaviour of the different samples indicates that 0.1 M NaCl, at 25 degrees C, is a good solvent of sodium pectinates. From the evolution of the Huggins parameter, it appears that pectins with 50% of methylated galacturonic groups exhibit a maximum flexibility. A Mark-Houwink exponent of 0.8 has been found in good agreement with theoretical predictions for flexible polymers in a good solvent.

Acetylation↗
PubMed1988

Effect of pectic substances on prolactin and growth hormone secretion in the ewe and on the induction of casein synthesis in the rat.

Pectins from apple, citrus and sugar beet injected intravenously to ewes markedly stimulated blood prolactin, growth hormone (GH) and cortisol. Pectic acid and polygalacturonic acid exhibited the same property. A preparation of oligogalacturonic acid with a polymerisation degree of 12 to 13 was also active, whereas oligomers with a smaller degree of polymerisation (congruent to 10) were devoid of activity. Pectic acid administered orally to mature virgin rats induced the accumulation of beta-casein in mammary gland. Pectins and some of their derivatives therefore had a lactogenic property and their effect probably resulted from a capacity to trigger lactogenic hormone secretion.

Administration, Oral↗