Biomedical subjects

Y Popineau

Publications and source records attributed to Y Popineau.

At least 19 recordsLinked to original sources

PubMed2006

Characterisation and foaming properties of hydrolysates derived from rapeseed isolate.

Two hydrolysis methods used to obtain rapeseed isolate derivates were compared: chemical hydrolysis performed under alkaline conditions and pepsic proteolysis performed under acidic conditions. The mean molecular weights obtained for the hydrolysates varied from 26 to 2.5 kDa, depending on the level of hydrolysis. Further characterisation showed that, at the same level of hydrolysis, the chemical hydrolysates differed by their charges and hydrophobicity from those derived from enzymatic digestion. Analysis of the foaming properties showed, for both cases, that a limited degree of hydrolysis, around 3%, was sufficient to optimise the foaming properties of the isolate despite the different physicochemical properties of the peptides generated. The study of foaming properties at basic, neutral and acidic pHs showed that the hydrolysate solutions yielded dense foams which drained slowly and which maintained a very stable volume under the three pH conditions tested.

Brassica rapa↗

PubMed2005

Identification of IgE-binding epitopes on gliadins for patients with food allergy to wheat.

BACKGROUND: Food allergy to wheat induces different symptoms as atopic eczema/dermatitis syndrome (AEDS), urticaria and more severe reactions as wheat-dependent exercise-induced anaphylaxis (WDEIA). Different gliadin classes are involved in this allergy but IgE-binding epitopes are known only on omega5-gliadins and for WDEIA cases. OBJECTIVES: The aim of the study was to identify IgE-binding epitopes on several gliadin classes and for several patients with different symptoms and ages. METHODS: Eleven sera were analysed by pepscan with overlapping synthetic peptides. RESULTS: Sera from five patients with anaphylaxis, urticaria or WDEIA, displayed strong IgE-binding to sequential epitopes of the repetitive domains of alphabeta, gamma, omega2 or omega5-gliadins with two immunodominant epitopes on omega5-gliadin and a consensus motif of the type QQX1PX2QQ (X1 being L, F, S or I and X2 Q, E or G). One patient allergic to deamidated wheat proteins also had IgE to a repetitive peptide of gamma and omega2-gliadins of the type QPQQPFP. Sera from four patients with AEDS detected no linear epitopes on gliadins, despite the fact that they contained specific IgE to alpha, beta, gamma or omega-gliadins. One child with AEDS recognized cysteine-containing sequences in the nonrepetitive domains of alphabeta and gamma-gliadins. CONCLUSION: B epitopes in wheat allergy were different from B epitopes of coeliac disease. Differences exist in IgE-binding epitopes between patients with food allergy to wheat. IgE from those suffering from WDEIA, anaphylaxis and urticaria detected sequential epitopes in the repetitive domain of gliadins whereas IgE from AEDS patients probably recognized conformational epitopes.

Adult↗

PubMed2004

Soy glycinin microcapsules by simple coacervation method.

Encapsulation of a dispersed oil phase (hexadecane) was realized by simple coacervation method using soy glycinin as the wall forming material. Suitable emulsification and coacervation conditions, that favor the formation of microcapsules wall, were identified and investigated. Mild acid (pH 2.0) and heat (55 degrees C) treatments of the reaction medium during the emulsification step enhanced significantly the deposition of coacervated glycinin around oil droplets. A pronounced correlation between glycinin concentration in the continuous phase, specific surface of the dispersed phase and the microencapsulation efficiency was also observed. Coacervation step study concerned the morphology and the stability of microcapsules. Controlled initiation of the coacervation, by slow readjustment of the pH, allowed a homogeneous precipitation of glycinin around oil droplets as well as the absence of aggregation phenomena. Since the morphology of microcapsules was considerably affected by a prolonged stirring of the reaction medium, the coacervation and reticulation time were optimized in order to preserve the homogeneity of the microcapsules size distribution and the microencapsulation efficiency.

Alkanes↗

PubMed2004

Microcapsules based on glycinin-sodium dodecyl sulfate complex coacervation.

Microcapsules processed by complex coacervation were prepared using hexadecane for the oil phase and glycinin (a soybean storage protein)-sodium dodecyl sulfate (SDS) as the main wall-forming material. The study underlines the essential role of SDS, which, by the way of [glycinin(+)-SDS(-)] insoluble complex formation, allowed the precipitation of proteins around oil droplets. Moreover, particular attention was attributed to the study of suitable conditions of glycinin cross-linking with glutaraldehyde. The reticulation step was performed at pH 4.0 and it was observed that the precipitated state of proteins increased considerably the efficiency of the cross-linking reaction. Analysis of the reactional medium after each main step of the process (emulsification, complex coacervation, cross-linking) allowed the follow-up and characterization of microcapsule formation. Optimization of different process parameters such as glycinin concentration, glycinin/SDS/glutaraldehyde ratios, pH and the kinetics of cross-linking allowed the encapsulation of the totality of oil and the use of more than 98% of initially introduced proteins for the microcapsule wall formation.

Capsules↗

PubMed2003

Molecular determinants of the influence of hydrophilic plasticizers on the mechanical properties of cast wheat gluten films.

The influence of a set of hydrophilic plasticizers varying in their chain length (ethyleneglycol and longer molecules) on the tensile strength and elongation at break of cast gluten films was studied. When considered on a molar basis (moles of plasticizer per mole of amino acid), the effect of the different plasticizers depended on their respective molecular weights for plasticizer/amino acid ratios in the range from 0.10 to 0.40. However, above a ratio of 0.40-0.50 mol/mol of amino acid, these differences were abolished and both stress and strain reached a plateau value, with all plasticizers studied. In fact, when a homologous series of molecules was considered, the ability for plasticizer to decrease stress and increase strain was closely related to the number of hydrogen bonds the molecule was able to share with the protein network. Ethyleneglycol's efficiency was, however, lower than expected from its hydrogen-bonding potential; a comparison with other diols demonstrated that this was due to the small size of this molecule. The particular effect of glycerol concentration on the films' mechanical properties suggested that other molecular features of the plasticizer, such as the number and position of hydroxide groups in the molecule, were involved in the plasticization mechanism.

Ethylene Glycol↗

PubMed2003

Food allergy to wheat: identification of immunogloglin E and immunoglobulin G-binding proteins with sequential extracts and purified proteins from wheat flour.

BACKGROUND: Cereal-associated allergy is particularly considered a serious problem, because cereals are essential in our daily diet. Wheat proteins are classified into albumins, globulins and prolamins (insoluble gliadins and glutenins). OBJECTIVES: Our objectives were to study the involvement in food allergy to wheat of these different protein types by using purified fractions and to identify those binding IgE and IgG antibodies. METHODS: Sera were obtained from 28 patients with food allergy to wheat. Albumins/globulins, gliadins and glutenins were obtained by sequential extraction based on differential solubility; alpha-, beta-, gamma- and omega-gliadins and low molecular weight (LMW) and high molecular weight (HMW) glutenin subunits were purified by chromatography. IgE binding to these extracts and fractions were analysed by radioallergosorbent test (RAST), and immunoblotting; IgG binding was detected by enzyme-linked immunosorbent assay (ELISA). RESULTS: In RAST, 60% of sera were shown to have specific IgE antibodies against alpha-, beta-gliadins and LMW glutenin subunits, 55% to gamma-gliadins, 48% to omega-gliadins and 26% to HMW glutenins. Immunoblotting analysis confirmed results obtained in RAST concerning LMW and HMW glutenin subunits and showed that 67% of patients have IgE antibodies to the albumin/globulin fraction. CONCLUSION: Results obtained in the different tests showed common features and in agreement with other studies indicated the presence of numerous allergens in food allergy to wheat; alpha-, beta-, gamma- and omega-gliadins, LMW glutenin subunits and some water/salt-soluble proteins appeared as major IgE binding allergens, whereas HMW glutenins were only minor allergens. The same type of antigenic profile against gliadins and glutenins was observed with IgG antibodies. Important sequence or structural homologies between the various gliadins and LMW glutenin subunits could certainly explain similarity of IgE binding to these proteins.

Adult↗

PubMed2002

Biopolymeric colloidal carriers for encapsulation or controlled release applications.

Biopolymers represent an interesting alternative to synthetic polymers in order to be used as structured carriers for controlled release and encapsulation applications. In particular, the ability of these carriers to entrap both hydrophilic and hydrophobic drugs may be very promising for many applications. In addition, the absence of chemical compounds and organic solvents used to produce biopolymeric matrices could be very interesting for some industrial applications. Simple or complex coacervation methods involving proteins or protein and polysaccharide mixtures were used to create new matrices dedicated to controlled release applications. Controlled release experiments with model compounds were conducted in order to evaluate the performance of such matrices. An alternative and promising research field deals with particles obtained from hydrogel systems. Totally transparent solid matrices resulting from the dehydration of new protein gels were formed and swelling capacities of these matrices were studied.

Biopolymers↗

PubMed2002

Development of an in vitro system simulating bucco-gastric digestion to assess the physical and chemical changes of food.

The release of nutrients from solid food depends on the physical and chemical characteristics of substrates, and on dynamic physiological events including pH, gastric emptying and enzymatic secretion. Our laboratory has developed an in vitro digestive system mimicking mouth and stomach processes to determine physical and chemical changes of bread during digestion. To simulate oral-phase digestion, bread was minced and subjected to in vitro amylase digestion, releasing 219 +/- 11 g oligosaccharides/kg total carbohydrate. During the gastric phase, bread proteins, which are converted into insoluble aggregated proteins during breadmaking, were emptied in various states of peptic digestion: undigested aggregated proteins and degraded proteins of intermediate and low molecular weight. The mean particle size of ground bread decreased progressively to the end of the gastric digestion (from 292 to 109 microm). The in vitro digestive system proved to be a useful tool for understanding the dynamic digestion of various food components held within the structure of a food matrix.

Bread↗

PubMed2001

Ultrafiltration to fractionate wheat polypeptides.

An ultrafiltration process allowing the fractionation of two kinds of polypeptides issued from limited chymotryptic hydrolysis of wheat gliadins was applied to wheat gluten hydrolysates. Hydrophilic and poorly charged polypeptides were well transmitted through an inorganic ZrO2-based membrane at acidic pH, whereas hydrophobic and positively charged polypeptides were highly retained. By combining reversed-phase and cation-exchange chromatography (CEC), it was proved that the fractionation of the polypeptides was based on electrostatic repulsion of the charged polypeptides by the positively charged membrane. After a continuous diafiltration process, retentates containing 75 to 88% of hydrophobic polypeptide and permeates containing 84 to 90% of hydrophilic polypeptides were recovered, depending on the size of membrane used. Even if the ultrafiltration fractions were less purified than fractions issued from CEC, it was shown that they exhibited very different foaming properties: permeate did not produce nor stabilize foams, whereas retentate was more efficient than the whole hydrolysates and BSA.

Chromatography, Gel↗

PubMed2001

Evolution of wheat gliadins conformation during film formation: a fourier transform infrared study.

The secondary structures of wheat gliadins (a major storage protein fraction from gluten) in film-forming solutions and their evolution during film formation were investigated by Fourier transform infrared spectroscopy. In the film-forming solution, wheat gliadins presented a mixture of different secondary structures, with an important contribution of beta-turns induced by proline residues. The presence of plasticizer did not have any influence on protein secondary structure in the film-forming solution. The evolution of protein conformation was followed during drying; the major feature of this evolution was a clear growing of the infrared band at 1622 cm(-1), characteristic of intermolecular hydrogen-bonded beta-sheets. This revealed the formation of protein aggregates during film drying. The influence of the drying temperature on film properties and gliadin secondary structures was also investigated. Higher drying temperatures induced an increase of both the tensile strength of the films and the amount of beta-sheets aggregates. Although the appearance of heat-induced disulfide bridge cross-links has already been described, there is clear evidence that hydrogen-bonded beta-sheets aggregates are also induced by thermal treatment. It was not possible, however, to determine whether there is a direct relationship between the occurrence of these aggregates and the increase of the tensile strength of the films.

Gliadin↗

PubMed2001

Prolamin aggregation, gluten viscoelasticity, and mixing properties of transgenic wheat lines expressing 1Ax and 1Dx high molecular weight glutenin subunit transgenes.

The composition of high molecular weight (HMW) subunits of glutenin determines the gluten strength and influences the baking quality of bread wheat. Here, the effect of transgenes coding for subunits 1Ax1 and 1Dx5 was studied in two near-isogenic wheat lines differing in their HMW subunit compositions and mixing properties. The subunits encoded by the transgenes were overexpressed in the transformed lines and accounted for 50-70% of HMW subunits. Overexpression of 1Ax1 and 1Dx5 subunits modified glutenin aggregation, but glutenin properties were much more affected by expression of the 1Dx5 transgene. This resulted in increased cross-linking of glutenin polymers. In dynamic assay, the storage and loss moduli of hydrated glutens containing 1Dx5 transgene subunits were considerably enhanced, whereas expression of the 1Ax1 transgene had a limited effect. The very high strength of 1Dx5 transformed glutens resulted in abnormal mixing properties of dough. These results are discussed with regard to glutenin subunit and glutenin polymer structures.

Chemical Phenomena↗

PubMed2001

Reversible changes of the wheat gamma 46 gliadin conformation submitted to high pressures and temperatures.

The structure of the wheat gamma 46 gliadin was investigated, in aqueous solutions, under high pressure or temperature by the use of ultraviolet and fluorescence spectroscopic techniques. We found that high pressure (above 400 MPa) induces a change in the protein conformation that results in a decrease of the polarity of the environment of aromatic amino acids. This new conformation was able to bind the hydrophobic probe, 8-anilino-1-naphtalene-sulfonic acid (ANS), indicating an increase in the gliadin surface hydrophobicity. Thermodynamic parameters of this conformational change were measured and infrared spectroscopy studies were used to probe the potential secondary structure modifications. The high stability of gamma 46 gliadin could be related to its elastic character, as the observed changes were always found to be reversible.

Anilino Naphthalenesulfonates↗

PubMed1999

Preparation of Ulex europaeus lectin-gliadin nanoparticle conjugates and their interaction with gastrointestinal mucus.

One approach to improve the bioavailability and efficiency of drugs consists of the association of a ligand (i.e. lectins), showing affinity for biological structures located on the mucosa surfaces, to nanoparticulate drug delivery systems. In this context, Ulex europaeus lectin-gliadin nanoparticle conjugates (UE-GNP) were prepared with the aim of evaluating their in vitro bioadhesive properties. The lectin was fixed by a covalent procedure to gliadin nanoparticles by a two-stage carbodiimide method. Typically, the amount of bound lectin was calculated to be approximately 15 microg lectin/mg nanoparticle, which represented a coupling efficiency of approximately 16% of the initial lectin concentration. In addition, the activity of these conjugates was tested with bovine submaxillary gland mucin (BSM) and the level of binding to this mucin was always much greater with UE-GNP than with controls (gliadin nanoparticles). However, the presence of 50 micromol fucose, which is the reported specific sugar for U. europaeus lectin, specifically inhibited the activity of these conjugates and, therefore, the UE-GNP binding to BSM was attenuated by 70%. These results clearly showed that the activity and specificity of U. europaeus lectin was preserved after covalent coupling to these biodegradable carriers.

Animals↗

PubMed1999

Fractionation of gliadin hydrolysates in water-ethanol by ultrafiltration with modified or unmodified membranes.

Ultrafiltration was applied to the fractionation of neutral vs. charged peptides of similar size. The peptides, produced from gliadins, a major fraction of wheat storage proteins, were obtained by limited hydrolysis with alpha-chymotrypsin in water-ethanol 80/20 (v/v). Peptides, according to their elution by RP-HPLC, were quasineutral (repetitive peptides) irrespective of pH, or positively charged (nonrepetitive peptides) at pH below 5. The transmission through the membranes of the nonrepetitive peptides was less (until sevenfold) than that of the repetitive ones, because of the role of electrostatic repulsion involved in the retention of charged solutes. The difference of transmission was more efficient at acidic pH (3) and low ionic strength with inorganic membranes and in a wider range of pH and ionic strength with membranes modified by coating of positively charged polymers (polyvinylimidazole PVI, polyethyleneimine PEI). A continuous diafiltration process using an inorganic membrane of low molecular cut-off permitted the selective enrichment of the retentate in nonrepetitive peptides (up to 80%) and of the permeate in repetitive peptides (up to 80%) from hydrolysate feed containing about 60/40% of repetitive and nonrepetitive peptides, respectively, with a diafiltration volume of 4.

Amino Acids↗

PubMed1999

Small angle X-ray scattering of wheat seed-storage proteins: alpha-, gamma- and omega-gliadins and the high molecular weight (HMW) subunits of glutenin.

Small angle X-ray scattering in solution was performed on seed-storage proteins from wheat. Three different groups of gliadins (alpha-, gamma- and omega-) and a high molecular weight (HMW) subunit of glutenin (1Bx20) were studied to determine molecular size parameters. All the gliadins could be modelled as prolate ellipsoids with extended conformations. The HMW subunit existed as a highly extended rod-like particle in solution with a length of about 69 nm and a diameter of about 6.4 nm. Specific aggregation effects were observed which may reflect mechanisms of self-assembly that contribute to the unique viscoelastic properties of wheat dough.

Gliadin↗

PubMed1998

Partial amino acid sequence of gamma-46 gliadin.

We have determined the partial amino acid sequence (207 amino acids) of gamma-46 gliadin isolated from wheat cultivar Hardi. The molecular mass of the protein (Mr) estimated by electrospray mass spectrometry is 35191.3. The number of cysteine residues in gamma-46 gliadin was determined as a mass difference of the protein before and after reduction and alkylation with 4-vinylpyridine. It was shown that the protein has no free SH-groups, and all cysteine residues are involved in the formation of four disulfide bonds. The partial structure of gamma-46 gliadin was determined by N-terminal sequencing and sequencing of tryptic and chymotryptic peptides. The tryptic peptides were obtained by enzymatic hydrolysis of the protein, which was preliminarily reduced and immobilized at free SH-groups on thiopropyl-Sepharose 6B. The chymotryptic peptides were isolated by limited digestion of the native protein. The positions of cysteine residues, as well as surrounding amino acid sequences, are conserved in gamma-46 gliadin; this is typical of gliadins.

Amino Acid Sequence↗

PubMed1997

Synthetic genes specifying periodic polymers modelled on the repetitive domain of wheat gliadins: conception and expression.

In order to optimise new polypeptide based biomaterials, we developed a procedure for producing homoblock polypeptides using recombinant DNA technology. Synthetic genes encoding periodic polypeptides modelled on the consensus sequence of wheat gliadins (a family of wheat storage proteins) were devised to be expressed in Escherichia coli. The construction strategy followed allows the construction of three genes encoding 8, 16, and 32 copies of the PQQPY module. The optimal expression conditions in the enterobacteria were established and a convenient purification procedure was shown to be useful in recovery of sizable amounts of strictly periodic polypeptides. The identities of the synthesized polypeptides were assessed using positive cross reactions to antibodies raised against a synthetic decapeptide (PQQPYPQQPA) and amino acid composition was determined as well.

Amino Acid Sequence↗

PubMed1996

Relations between aggregative, viscoelastic and molecular properties in gluten from genetic variants of bread wheat.

Glutens differing in their low- and high-molecular-weight glutenin subunits (LMW-GS and HMW-GS) were extracted from genetic variants of bread wheat. Their composition was analysed by electrophoresis, the glutenin size distribution was determined by size-exclusion chromatography. Rheological measurements in the dynamic regime and electron spin resonance spin-labelling experiments gave data on the viscoelasticity and the protein flexibility of the glutens, respectively. In glutens differing in their HMW-GS, a relation is observed between the composition, aggregative properties, segmental flexibility and viscoelastic behaviour. This is not found in glutens with different LMW-GS. However, the proportion of rigid polypeptide segment is related to the height of the elastic plateau in all cases. The organisation of the protein network in gluten is discussed in reference to this data.

Electron Spin Resonance Spectroscopy↗