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Casein Fraction (casein + fraction)
Selected AbstractsFractionation of Caseins by Anion-exchange Chromatography Using Food-grade BuffersJOURNAL OF FOOD SCIENCE, Issue 5 2003K.N. Turhan ABSTRACT : Caseins prepared by microfiltration of bovine skim milk were fractionated using anion-exchange chromatography. Laser densitometry of electrophoresis gels was shown to be sufficiently quantitative to perform accurate mass balance calculations detailing the fate of each casein fraction. L-cysteine was successfully used as a reducing agent instead of traditional toxic agents, such as dithiothreitol or ,-mercaptoethanol, enabling development of the first food-grade buffer system for casein fractionation. More salt was required for elution of the casein fractions having a greater charge: ,s -casein > ,-casein > ,-casein. Increasing flow rate decreased the extent of separation. Use of smaller beads was suggested as a method to maintain separation at increased flow rate. [source] Analysis of trace amounts of bovine ,-lactoglobulin in infant formulas by capillary electrophoresis with on-capillary derivatization and laser-induced fluorescence detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9-10 2005Marķa Teresa Veledo Abstract Bovine ,-lactoglobulin (,LG) has been described by several authors as the main allergen present in cow's milk. It can induce allergic reactions even at the low concentration existing in hypoallergenic formulas based on hydrolyzed cow's milk proteins (generally lower than ,M). In this paper, the usefulness of a capillary electrophoresis method with on-capillary derivatization and laser-induced fluorescence detection for the analysis of trace amounts of ,LG in a commercial hypoallergenic formula has been demonstrated. To confirm the identity of the peak of ,LG based on migration time, an immunorecognition step employing an anti-,LG antibody was performed. ,LG was quantitated in the whey and casein fractions of the hypoallergenic formula. The concentration of ,LG in the whey fraction of the formula was about 3 orders of magnitude lower than the average value present in cow's milk. In the casein fraction of the formula, the concentration of ,LG was about 1 order of magnitude lower than in the whey fraction. The method developed was also used for the quality control of three cereal-based infant foods formulated without milk to test the presence or absence of ,LG as an indicator of milk contamination during the fabrication process. ,LG in a concentration of 10,7 M or higher was not observed in any of the cereal-based infant formulas analyzed. [source] Allergy to goat and sheep milk without allergy to cow's milkALLERGY, Issue 11 2006S. Ah-Leung Background:, Cow's milk (CM) allergy is the most frequent cause of food allergy in infants. Most children who are allergic to CM are also sensitized to whey proteins and/or to the casein fraction and many of them cannot tolerate goat's or sheep's milk (GSM) either. Conversely, the GSM allergies that are not associated with allergic cross-reactivity to CM are rare. Methods:, Twenty-eight children who had severe allergic reactions, including anaphylaxis, after consumption of GSM products but tolerated CM products were recruited in a retrospective study. Whole casein and whey proteins were fractionated from CM and GSM. , -Lactoglobulin and the different caseins were isolated, purified and used to perform enzyme allergosorbent tests (EAST) and EAST inhibition studies with the sera of the allergic children. Results:, Clinical observations, skin prick testing and immunoglobulin (Ig)E-binding studies confirmed the diagnosis of GSM allergy without associated CM allergy. EAST determinations demonstrated that GSM allergy involves the casein fraction and not whey proteins. Cow's milk caseins were not at all or poorly recognized by the patient's IgE, while ,S1 -, ,S2 - and , -caseins from GSM were recognized with a high specificity and affinity. In all cases, increasing concentrations of CM caseins failed to inhibit the binding of patient's IgE to sheep or goat milk caseins, whereas this binding was completely inhibited by GSM caseins. Conclusions:, The characteristics of GSM allergy differ from those of the CM allergy because it affects older children and appears later. CM products do not elicit any clinical manifestation in GSM allergic patients, whereas CM allergic patients, usually cross-react to GSM. In all the GSM allergic children, the IgE antibodies recognized the caseins but not the whey proteins. Moreover, IgE specificity and affinity was high to GSM and lower to CM caseins despite their marked sequence homology. Doctors and allergic individuals should be aware that GSM allergy requires a strict avoidance of GSM and milk-derived products because reactions could be severe after ingestion of minimal doses of the offending food. [source] Sequence and phosphorylation level determination of two donkey , -caseins by mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2009Vincenzo Cunsolo Two coeluting components, with experimentally measured Mr values of 25529 and 24606 Da, were identified by reversed-phase high-performance liquid chromatography (RP-HPLC) and mass spectrometric analysis in the dephosphorylated casein fraction of a milk sample collected from an individual donkey belonging to the Ragusano breed of the east of Sicily. By coupling enzymatic digestions, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and RP-HPLC/nano-electrospray ionization tandem mass spectrometry (nESI-MS/MS) analysis, the two proteins were identified as donkey , -CNs and their sequences characterized completely, using the two known , -CNs from mare as references. The two donkey , -CNs, showing a mass difference of 923 Da, differ by the presence of the domain E27SITHINK34 in the full-length component (Mr 25529 Da). In comparison with the mare's , -CNs used as reference, they present nine amino acid substitutions: L,S37, R,H52, S,N81, P,V84, L,V91, R,Q203, P,L/I206, L,F210 and A,P219. Together, these substitutions account for the increase of 18 Da in the Mr of the donkey , -CNs with respect to the counterparts from the mare. The molecular mass determination by ESI-MS for the phosphorylated proteins showed that the full-length component was composed of highly multi-phosphorylated isoforms with five to seven phosphate groups. By analogy with the homologous mare's , -CNs, the full-length (226 amino acids) , -CN was termed variant A, whereas the shorter (218 amino acids) , -CN was termed variant A,5. Copyright © 2009 John Wiley & Sons, Ltd. [source] Identification and characterization of a new , -casein variant in goat milk by high-performance liquid chromatography with electrospray ionization mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2004Francesco Galliano A new variant of , -casein was detected in the casein fraction obtained from milk of a goat belonging to an autochthonous breed of southern Italy, ,Argentata dell'Etna'. Reversed-phase high-performance liquid chromatography/electrospray ionization mass spectrometry (RP-HPLC/ESI-MS) analysis indicated that the new , -casein variant, here named D, has a Mr 15,Da higher than that of variant C previously described. The modification in the amino acid sequence responsible for the 15,Da difference in Mr between variants C and D was determined by coupling trypsin digestion with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and RP-HPLC/ESI-MS, and it was demonstrated that it is due to the point mutation Val207,,,Asn207. The phosphorylation pattern of the new variant D was shown to be identical to that of variant C, as the protein shows two phosphorylation levels, 5 and 6P, occurring with comparable relative abundances. Ser35 was determined as one of the phosphorylation sites, whereas the others were probably analogous to those determined previously for the , -Cn variant C, at Thr12 and Ser15, 17,19. The results reported here indicate that the combined use of RP-HPLC/ESI-MS, MALDI-TOFMS and MS/MS represents a powerful tool for the detection and characterization of minor components present in complex protein mixtures. Copyright © 2004 John Wiley & Sons, Ltd. [source] Fractionation of Caseins by Anion-exchange Chromatography Using Food-grade BuffersJOURNAL OF FOOD SCIENCE, Issue 5 2003K.N. Turhan ABSTRACT : Caseins prepared by microfiltration of bovine skim milk were fractionated using anion-exchange chromatography. Laser densitometry of electrophoresis gels was shown to be sufficiently quantitative to perform accurate mass balance calculations detailing the fate of each casein fraction. L-cysteine was successfully used as a reducing agent instead of traditional toxic agents, such as dithiothreitol or ,-mercaptoethanol, enabling development of the first food-grade buffer system for casein fractionation. More salt was required for elution of the casein fractions having a greater charge: ,s -casein > ,-casein > ,-casein. Increasing flow rate decreased the extent of separation. Use of smaller beads was suggested as a method to maintain separation at increased flow rate. [source] Analysis of trace amounts of bovine ,-lactoglobulin in infant formulas by capillary electrophoresis with on-capillary derivatization and laser-induced fluorescence detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9-10 2005Marķa Teresa Veledo Abstract Bovine ,-lactoglobulin (,LG) has been described by several authors as the main allergen present in cow's milk. It can induce allergic reactions even at the low concentration existing in hypoallergenic formulas based on hydrolyzed cow's milk proteins (generally lower than ,M). In this paper, the usefulness of a capillary electrophoresis method with on-capillary derivatization and laser-induced fluorescence detection for the analysis of trace amounts of ,LG in a commercial hypoallergenic formula has been demonstrated. To confirm the identity of the peak of ,LG based on migration time, an immunorecognition step employing an anti-,LG antibody was performed. ,LG was quantitated in the whey and casein fractions of the hypoallergenic formula. The concentration of ,LG in the whey fraction of the formula was about 3 orders of magnitude lower than the average value present in cow's milk. In the casein fraction of the formula, the concentration of ,LG was about 1 order of magnitude lower than in the whey fraction. The method developed was also used for the quality control of three cereal-based infant foods formulated without milk to test the presence or absence of ,LG as an indicator of milk contamination during the fabrication process. ,LG in a concentration of 10,7 M or higher was not observed in any of the cereal-based infant formulas analyzed. [source] | ||||||||||