Electric field effects on β-lactoglobulin thermal unfolding as a function of pH Impact on protein functionality

The presence of moderate electric fields (MEF) during ohmic heating (OH) treatment of whey protein systems have demonstrated potential to change physicochemical and functional properties, like aggregation rate and extension or viscoelastic behaviour. However, the specific action of MEF upon the molecular structure of proteins, particularly during thermal processing has yet to be clarified. The effects of MEF in pure fractions of -lactoglobulin (β-lg) under non-aggregating conditions (low concentration and ionic strength), were investigated in this work. Protein samples were identically heat-treated through conventional and OH methods and at different pH values. β-lg's structural features were characterized by evaluation of secondary structure distribution and local conformational changes using techniques such as circular dichroism, intrinsic and extrinsic fluorescence and free thiol groups reactivity. It was confirmed that MEF affects β-lg upon thermal unfolding, resulting in distinctive structural features, surface hydrophobicity and SH reactivity. The mechanism of action is probably related with the molecular motion induced by the oscillating electric field and is more pronounced at neutral pH, where β-lg is more susceptible to thermal structural changes. These results contribute to a better understanding of OH processing and its effects in food matrices reinforce the possibility of using MEF as a toll to change protein functionality. Industrial relevance Ohmic heating is an emerging technology and is being established as reference method for processing protein-rich food such as dairy and egg products. Non-thermal effects of the applied electric fields during ohmic heating have been addressed but few works deal with their real impact in structural and molecular properties of food proteins with high biological value. In this work demonstrated that the presence of an electric field during ohmic heating processing influences structural aspects of beta-lactoglobulin. This knowledge plays an important role on process design (i.e. pasteurization binomials and fouling control) and product quality because these proteins play an essential role in food's nutritional and organoleptic properties, as well as on functionality, allergenicity and stability aspects.FCT -Fuel Cell Technologies Program(NORTE-01-0145-FEDER-000004)info:eu-repo/semantics/publishedVersio

Avances en modelos de análisis de estructuras de barras de hormigón frente a combinaciones de esfuerzos normales y tangentes

A pesar del gran desarrollo de los modelos de barras para el análisis estructural, estos modelos presentan, en general, carencias importantes cuando las estructuras son sensibles a esfuerzos tangenciales (cortante, torsión) o cuando existen estados tridimensionales complejos. Estas solicitaciones, muy comunes en las estructuras de ingeniería civil, son mucho más complejas de analizar en el caso de materiales que presentan comportamiento anisótropo dependiente de la carga, como es el caso del hormigón armado. Se presentan los modelos desarrollados en los últimos años para tener en cuenta este comportamiento satisfactoriamente, facilitando así el análisis de estructuras bajo fuertes combinaciones de esfuerzos normales y tangentes, como pueden darse en estructuras bajo acciones sísmicas

Determination of thermally-induced conformational slides in β-lactoglobulin prior to irreversible thermal denaturation

IFT 2017 Annual Meeting and Food Expo[Excerpt] Introduction: β-lactoglobulin (β-Lg) is the major globular protein in milk and the dominant functional agent in whey and its derivatives ingredients. It is generally recognized that β-Lg undergoes conformational changes above temperatures of 60 °C and unfolds irreversibly after 70 °C. The conformational changes that happen during this process have critical implications in β-Lg functional properties, thus affecting both technological quality of milk (i.e. cheese production) and whey ingredients, which use are currently widespread in food formulations. In this study thermal effects in β-Lg have been investigated through an innovative approach, combining on-line spectroscopy techniques, aiming at achieving a more detailed characterization of these events below and above the melting temperature. [...]This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. The authors Rui M. Rodrigues, Ricardo N. Pereira, also thank to FCT their financial grants with SFRH/BD/110723/2015, SFRH/BPD/81887/2011 respectively.info:eu-repo/semantics/publishedVersio

Complete enzymic synthesis of the mucin-type sialyl Lewis x epitope, involved in the interaction between PSGL-1 and P-selectin

Sialyl Lewis x (sLex) is an established selectin ligand occurring on N- and O-linked glycans. Using a completely enzymic approach starting from p-nitrophenyl N-acetyl-α-D-galactosaminide (GalNAc(α1-pNp as core substrate, the sLex-oligosaccharide Neu5Ac(α2-3)Gal(β1-4)[Fuc(α1-3)]GlcNAc(β1-6)[Gal(β1-3)]GalNAc(α1-pNp, representing the O-linked form, was synthesized in an overall yield of 32%. In a first step, Gal(β1-3)GalNAc(α1-pNp was prepared in a yield of 52% using UDP-Gal and an enriched preparation of β3-galactosyltransferase (EC 2.4.1.122) from rat liver. UDP-GlcNAc and a recombinant affinity-purified preparation of core 2 β6-N-acetylglucosaminyltransferase (EC 2.4.1.102) fused to Protein A were used to branch the core 1 structure, affording GlcNAc(β1-6)[Gal(β1-3)]GalNAc(α1-pNp in a yield of >85%. The core 2 structure was galactosylated using UDP-Gal and purified human milk β4-galactosyltransferase 1 (EC 2.4.1.38) (yield of >85%), then sialylated using CMP-Neu5Ac and purified recombinant α3-sialyltransferase 3 (EC 2.4.99.X) (yield of 87%), and finally fucosylated using GDP-Fuc and recombinant human α3-fucosyltransferase 6 (EC 2.4.1.152) produced in Pichia pastoris (yield of 100%). Overall 1.5 µmol of product was prepared. MALDI TOF mass spectra, and 1D and 2D TOCSY and ROESY 1H NMR analysis confirmed the obtained structur

Effects of moderate electric fields in beta-lactoglobulinthermal denaturation: structural changes and binding properties

This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2019 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. Rui M. Rodrigues gratefully acknowledge FCT for their financial grant with reference SFRH/BD/110723/2015.info:eu-repo/semantics/publishedVersio

Húmus de esterco bovino e casca de arroz carbonizada omo substrato para a produção de mudas de boca-de-leão.

Este trabalho teve como objetivo avaliar a eficiência de diferentes substratos constituídos à base de casca de arroz carbonizada e húmus de minhoca na produção comercial de mudas de bocade-leão (Antirrhinum majus L.). O experimento foi conduzido em casa de vegetação na Universidade Federal de Santa Maria, RS, no período de setembro a outubro de 2007. O delineamento experimental foi inteiramente casualizado, com sete tratamentos e quatro repetições, cada uma constituída por 72 alvéolos. As determinações realizadas nos substratos foram: densidade do substrato, porosidade total, espaço aéreo, água disponível e água remanescente como características físicas e potencial de hidrogênio, teor de macronutrientes e matéria orgânica como características químicas, além da avaliação da consistência do torrão. Nas plantas, foram determinadas: a altura, o número de pares de folhas e a biomassa fresca e seca da parte aérea. A casca de arroz carbonizada e o húmus podem ser utilizados para a constituição de substratos para a produção comercial de mudas, exceto na forma pura. Os maiores valores de massa seca, altura da muda e número de pares de folhas, foram observados nas mudas produzidas nos substratos cuja densidade encontrou-se na faixa de 0,18 a 0,33 g cm-3, sendo que estes mesmos substratos apresentaram os maiores valores de estabilidade do torrão. Concluiu-se que os substratos casca de arroz carbonizada e húmus de minhoca nas proporções de 80% casca de arroz carbonizada e 20% húmus, 60% casca de arroz carbonizada e 40% húmus, 50% casca de arroz carbonizada e 50% húmus e 40% casca de arroz carbonizada e 60% húmus apresentam potencial para serem utilizados para a produção de mudas de boca-de-leão