Thesis (Ph. D.)--University of Michigan, 1936. / Cover title. Caption title: Enzymatic hydrolysis of lactalbumin, by Lila Miller and Herbert O. Calvery. "Reprinted from the journal of biological chemistry, vol. 116, no. 1 ... November, 1936." Bibliography: p. 408.

Thesis (Ph. D.)--University of Michigan, 1936. / Cover title. Caption title: Enzymatic hydrolysis of lactalbumin, by Lila Miller and Herbert O. Calvery. "Reprinted from the journal of biological chemistry, vol. 116, no. 1 ... November, 1936." Bibliography: p. 408.

Frankfurt (Main), Univ., Diss., 2008

It is well known that DNA methylation in gene promoter regions inhibits gene transcription and that tissue-specific gene expression is partially under the control of this transcription regulatory mechanism. In this study, bovine mammary gland tissues were collected from individual animals in lactating and non-lactating stages to investigate the DNA methylation patterns in the kappa-casein gene and alpha-lactalbumin gene core promoter regions using the bisulphite treatment in combination with polymerase chain reaction (PCR) sequencing. Different methylation status of each sample was classified into three categories, namely methylation at known transcription factor binding domains, methylation at core promoter non-binding domains and the absence of cytosine methylation. Real-time quantitative PCR was used to quantify the transcription levels of the kappa-casein and alpha-lactalbumin genes from the collected samples. A comparative method was used and fold-change values were calculated based on the comparison of the normalized threshold values of samples from different physiological stages as well as on various methylation patterns observed in their core promoter regions. Statistical analyses showed that the expressions of the kappa-casein and alpha-lactalbumin genes were significantly different in lactating and non-lactating mammary gland tissues. The methylation observed in the core promoter region of bovine alpha-lactalbumin gene was found to be associated with its gene expression. On the other hand, the methylation found in the core promoter region of bovine kappa-casein gene did not have any effect on its gene transcript levels.

No description available.

Orientador: Valdemiro Carlos Sgarbieri / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-04T13:50:25Z (GMT). No. of bitstreams: 1 Mezzaroba_LeoniceFatimaHoger_M.pdf: 1147865 bytes, checksum: 8e30210b748cf78769bb1bcfbba59462 (MD5) Previous issue date: 2005 / Resumo: A a-lactalbumina tem sido recentemente associada com redução de estresse, imunomodulação, atividade antimicrobiana após proteólise, propriedade anticancer e atividade antiulcerogênica. Os objetivos deste trabalho foram definir uma metodologia para a obtenção da a-lactalbumina e da b-lactoglobulina a partir de um concentrado de proteínas de soro de leite bovino e investigar a atividade antiulcerogênica da a-lactalbumina (produzida em laboratório e uma preparação comercial), da a-lactalbumina comercial hidrolisada e duas frações de seu hidrolisado (F1 < 1kDa e F2 > 1kDa) na proteção da mucosa gástrica em modelos de úlcera induzida por indomentacina e etanol absoluto em ratos, bem como, avançar na investigação das vias metabólicas de ação protetora. Para o isolamento da a-lactalbumina e da b-lactoglobulina a partir do concentrado de soro de leite bovino utilizou-se o sistema FPLC da Pharmacia e coluna de troca aniônica (resina Q Sepharose fast flow), e a fração correspondente a a- lactalbumina foi em seguida purificada por exclusão molecular utilizando-se a resina Sephacryl S-200. A b-lactoglobulina foi facilmente isolada por cromatografia de troca iônica apresentando-se quase homogênea e com um rendimento de 82%; para a a-lactalbumina, foi necessária uma etapa de purificação, e a proteína semi purificada apresentou contaminantes e baixo rendimento (32%). Para avaliar a ação antiulcerogênica da a-lactalbumina e de seus hidrolisados em modelo de úlcera induzido por indomentacina ou por etanol absoluto os animais receberam duas doses das amostras teste em dias consecutivos. Para avaliar possíveis vias de ação protetora foram estudadas suas participações na secreção ácida gástrica através da ligadura do piloro, a participação de substâncias sulfidrila e prostaglandinas na citoproteção gástrica em modelos de úlcera induzida por etanol absoluto. A a-lactalbumina comercial (Davisco Foods International, INC.) foi à amostra que apresentou maior porcentagem de inibição do índice de lesões ulcerativas no modelo de úlcera induzida por indometacina. No modelo de úlcera induzida por etanol absoluto, a a-lactalbumina (produzida em laboratório e a comercial) e frações de seu hidrolisado (F1 e F2) inibiram as lesões gástricas em níveis significativos na mesma ordem. A investigação das vias metabólicas de ação protetora, mostrarram que as amostras não alteraram a concentração ácida total após 4 horas de piloro ligado, sugerindo que a atividade antiulcerogênica desta proteína parece não ser mediada pela via da secreção ácida gástrica. A alquilação de grupamentos sulfidrila, envolvidos no mecanismo de citoproteção gástrica com N-etilmaleimida (NEM), eliminou o efeito protetor da a-lactalbumina e de frações de seu hidrolisado à mucosa gástrica, sugerindo que a ação antiulcerogênica parece depender da participação destas substâncias. A inibição da síntese de prostaglandina pela indometacina, bloqueador da síntese de prostaglandinas pela inibição da ciclooxigenase, não impediu que a a-lactalbumina (produzida em laboratório e a comercial) e a fração do hidrolisado de peso molecular >1kDa protejesse a mucosa gástrica a níveis significativos, sugerindo uma menor dependência de prostaglandina para a ação protetora dessas amostras. Já a fração do hidrolisado de peso molecular <1kDa perdeu sua atividade, evidenciando a participação de prostaglandinas na citoproteção gástrica por esta fração peptídica. A confirmação do envolvimento de prostaglandinas no mecanismo de ação antiulcerogênica por peptídios derivados da a-lactalbumina foi realizada através da quantificação do muco gástrico e da determinação da concentração de PGE2 na mucosa gástrica. Os resultados obtidos sugerem que há um conjunto de mecanismos envolvidos na proteção exercida pela a- lactalbumina e frações de seu hidrolisado enzimático sobre a mucosa gástrica, sendo estes, a participação de substâncias sulfidrila e aumento dos níveis de prostaglandina E2 na mucosa gástrica / Abstract: The a-lactalbumin has been recently associated with reduction of stress, immunomodulation, antimicrobial activity after proteolysis, anticancer and antiulcerogenic activity. The purpose of this work was to define a methodology for obtaing a-lactalbumin and b-lactoglobulin from a bovine whey protein concentrate and to investigate the antiulcerogenic activity of the a-lactalbumin (produced in laboratory and a commercial preparation ¿ Davisco Foods International, INC.), of the hidrolyzed commercial a-lactalbumin and two fractions of this hidrolysate (F1<1kDa and F2 >1kDa), in the protection of gastric mucosa induced by indomethacin or absolute ethanol induced ulcer in rats, as well as, to advance in the inquiry of the metabolic pathways of protective actions. For the isolation of the a-lactalbumin and of b-lactoglobulin from the bovine whey protein concentrate a Pharmacia FPLC system with anion exchange column (Q-Sepharose fast flow resin) was used. Alpha-lactalbumin was further purified by molecular exclusion chromatography using Sephacryl S-200 column. The b-lactoglobulin was easily isolated from ionic exchange chromatography presenting good purity and 82% yield; for the a-lactalbumin, a second stage of purification was necessary, and the partially purified protein still presented some contaminants and a low yield (35%). To evaluate the antiulcerogenic action of the a-lactalbumin and its hidrolysates for indomethacin and absolute ethanol induced ulcer in rats, the animals received two doses of the samples in consecutive days. To determine possible mechanisms of protection to the gastric mucosa, the effect in the gastric acid secretion through the tied piloro technique, the participation of sulfhydryl substances and prostaglandins were studied. For the indomethacin induced ulcer only the commercial a- lactalbumin inhibited the gastric injuries, while in the absolute ethanol induced ulcer all the samples were able to reduce the gastric injuries at significant levels. The inquiry of the metabolic pathways of protective action showed that the samples did not modify the concentration of the total acid after 4 hours tied piloro, suggesting that the antiulcerogenic activity of these proteins and peptides seem not to be mediated by the mechanism of gastric acid secretion. The alkylation of sulfhydryl groups with N-ethylmaleimide (NEM), partially eliminate the protective effect of the a-lactalbumin and its hidrolysates on the gastric mucosa, suggesting the participation of these groups in the antiulcerogenic action. The inhibition of the prostaglandin synthesis with indomethacin did not eliminate the protection offered by a-lactalbumin and the hydrolysate fraction of molecular weight > 1kDa. However the protection offered by the hydrolysate fraction of molecular weight < 1kDa was completely neutralysed by the indomethacin cycloxygenase inhibition, suggesting that a-lactalbumin low peptides seem to protect the gastric mucosa via the prostaglandin cycle. The confirmation of the envolvement of prostaglandins in the mechanism of antiulcerogenic action by a-lactalbumin peptides was substanciated through the quantification of gastric mucus and the determination of the PGE2 concentration in the gastric mucosa. These results suggest that there are more than one mechanism for the stomach cytoprotection against ulcerogenic factors a-lactalbumin and its hydrolysates. While intact a-lactalbumin and high molecular weight peptides seem to depend on the sulfhydryl groups for protection, low molecular weight peptides (MW < 1kDa) seem to act by stimulation of prostaglandin synthesis / Mestrado / Mestre em Alimentos e Nutrição

No description available.

Master of Science / Department of Food Science / Karen A. Schmidt / People who suffer from swallowing disorders are diagnosed with dyphasgia. The beverage for the dyphagia patients should have the apparent viscosity in the range of nectar-like (51 to 350 mPa•s) or honey-like (351 to 1750 mPa•s). Due to the swallowing problems, dysphagia patients usually consume beverages slowly. Thus, the apparent viscosity of beverage for such patients should be high enough to be in the suitable range during the entire time of consumption. Three ratios of α-lactalbumin (α-la)/β-lactoglobulin (β-lg) (3:8, 1:1 and 8:3) were used to prepare the milk systems. These ratio adjusted milk systems were either processed at 70, 80, and 90ºC for 30 min or at 25ºC, and cooled to 25 ± 1ºC. After the process was completed, the milk systems were set quiescently 120 min at 25 ±1ºC. Physical and chemical properties were assessed at various time. For the milk systems at 0 min, the apparent viscosity increased in all 90°C processed-samples, and the increase was in the order of 8:3 (15.96%), 1:1 (6.38%) and 3:8 (2.11%) compared with the 25ºC samples at each ratio. When the milk systems set for 120 min, apparent viscosity increased slightly by 3.7%. The maximum apparent viscosity was 2.18 mPa•s, which was less than nectar-like. Therefore, xanthan gum was added at 0.15 w/w % to enhance rheological properties of the milk systems. α-La/β-lg ratio adjusted milk systems either with or without xanthan gum were prepared, and processed at 90ºC or 25ºC, and cooled to 25 ± 1ºC. Apparent viscosity increased by 48.61 and 89.61% in 3:8 and 8:3 milk systems, respectively for those at 0.15% xanthan gum concentration and processed at 90ºC compared with at 25ºC. Apparent viscosity of 8:3 milk systems at xanthan gum concentration of 0.15% processed at 90°C was 58.7 ± 2.12 mPa•s which was within the nectar-like range. When the samples were set for 120 min, no changes were found in the apparent viscosity of the milk systems. If the rheological properties of the milk systems can be controlled by ingredients interactions, this can be used to develop nutritious products with different forms for dysphagia patients.

The problem of age gelation in ultra-high temperature (U1IT) sterilized milk retentate (ultrafiltered 3x concentrated) is investigated in this work. Transmission electron microscopy (1EM), utilizing the microcube encapsulation technique and protocols for immunolocalization of milk proteins, provides insight into the phenomenon of age gelation ofUHT-sterilized, ultrafiltered (UF) milk retentate. Primary antibodies (specific for the native as well as the complexed forms of milk proteins) and secondary antibodies (conjugated to gold probes) are used to elucidate the positions of the milk proteins in various samples of milk from the stage of milking through UHT sterilization and storage for 12 months, by which time gelation had occurred. The movement of the milk proteins is charted and these data are used to determine the role of the proteins in age gelation of UHT-sterilized UF milk retentate. Heat-denatured β-lactoglobulin and α-lactalbumin form complexes within the serum as well as with the casein components of the micelles. UHT sterilization not only denatures β-lactoglobulin and α-lactalbumin, but catalyzes the reaction of these whey proteins and K-casein, leading to the successful formation of the complex. Complexing of β-lactoglobulin and K-casein competitively weakens the complex of K-casein to other casein fractions of the micelle. This leads to migration of K-casein from the micelle to the serum, compromising the role of K-casein in stabilizing the casein proteins within the micellar moiety. The time-dependent loss of K-casein from the micelle would expose the calcium-insoluble micellar αs1-casein and β-casein to the serum calcium. Subsequent to this, some αs1-casein and β-casein are also released from the micelles, and gelation of the milk occurs. No information was obtained on location of αs2-casein. The release of K-casein from the micelles thus apparently represents the critical factor in the phenomenon of age gelation in UHT-sterilized milk concentrates.

In this thesis, mechanisms for enhancing the stability of whey protein emulsions using two approaches were investigated. First, the physicochemical and emulsifying properties of whey protein isolate (WPI), and its two main proteins, alpha-lactalbumin (ALA) and beta-lactoglobulin (β-LG), were investigated in response to changes in pH and temperature pre-treatments. Solvent conditions which inhibit protein aggregation, such as pHs away from the isoelectric point, were found to form stable emulsions. In contrast, thermal treatments were found to negatively affect emulsion stability, where the most stable emulsions for WPI, ALA and β-LG were formed at room temperature (i.e. 25°C) at pH 7.0. It was also determined that emulsions formed using WPI, ALA and β-LG were stabilized by electrostatically repulsive forces which prevent flocculation and creaming. Secondly, the use of tailored protein-polysaccharide interactions involving WPI and carrageenan (CG) were explored as a means of enhancing emulsion stability. Carrageenan (CG) partakes in electrostatic attraction with WPI when acidified, leading to the formation of coupled gel networks. CG was selected for its anionic properties and for its well-characterized structure in that kappa-, iota- and lambda-type CG contain 1-, 2- and 3-sulfated groups per disaccharide repeating unit respectively. WPI-CG mixtures formed gel networks once acidified, where WPI-kappa-CG and WPI-iota-CG mixtures formed stiff networks, whereas WPI-lambda-CG formed a weak fluid network. WPI-CG complexes were found to be surface active, causing changes to the interfacial tension and interfacial rheology at pHs corresponding to where electrostatic attraction occurs upon acidification. Electrostatically coupled gel networks were formed in an emulsion, where oil droplets became entrapped within the biopolymer matrix. WPI-CG mixtures were sensitive to WPI-CG mixing ratio as stiffer gels were formed at higher CG content. Furthermore, WPI-iota-CG gels were stiffer than those made with WPI-kappa-CG gels presumably due to the higher number of sulfated groups lending greater opportunities for iota-CG to form bonds with neighboring polymers compared to kappa-CG.