Influence of ohmic heating on the structural and immunoreactive properties of soybean proteins

Ohmic heating (OH) encompasses interesting benefits towards thermal processing. Envisaging an increasing relevance of soybean protein as an alternative non-animal protein, it is important to understand how OH can contribute to the quality and immunoreactivity of soybean-derived products. This study describes, for the first time, the impact of OH when applied at different electrical frequencies (50 Hz20 kHz) and moderate electric field intensities (up to 20 V/cm), on the leakage of metals from the electrodes and immunoreactivity aspects of soybean protein isolate (SPI). This was achieved by monitoring the occurrence of electrochemical reactions and evaluating IgG-binding capacity. OH performed at 50 Hz and 95 °C induced significant alterations on the intrinsic fluorescence of SPI (p  0.05) and the release of detectable amounts of Fe/Ni, with a subsequent reduction of 36% in the immunoreactivity of Gly m TI. The occurrence of non-thermal effects, as well as the interaction between protein and trace metals, may result in a partial blockage of protein epitopes, thus impairing specific antibody binding. These findings present novel information about the importance of OH parameters, such as electrical frequency and occurrence of electrochemical reactions, which can affect the structure and immunoreactivity of SPI fractions.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 and UID/QUI/50006/2020 with funding from FCT/MCTES through national funds, and AgriFood XXI R&D&I project, operation number NORTE-01-0145-FEDER-000041 and NORTE-01-0145-FEDER 000052, co-financed by the European Regional Development Fund (FEDER) through NORTE 2020 (Northern Regional Operational Pro gram 2014/2020). This work also received financial support from the European Union (FEDER funds through COMPETE POCI-01-0145- FEDER-031720) and National Funds (FCT) through project Alle Risk Assess PTDC/BAA-AGR/31720/2017. Caterina Villa and Luís Machado thank FCT for their grants under project AlleRiskAssess (PTDC/BAA-AGR/31720/2017). Joana Costa thanks FCT for funding through program DL 57/2016 – Norma transitoria (SFRH/BPD/102404/2014). Ricardo N. Pereira acknowledge FCT for its Assistant Research contract obtained under CEEC Individual 2017.info:eu-repo/semantics/publishedVersio

Misfolded proinsulin in the endoplasmic reticulum during development of beta cell failure in diabetes

The endoplasmic reticulum (ER) is broadly distributed throughout the cytoplasm of pancreatic beta cells, and this is where all proinsulin is initially made. Healthy beta cells can synthesize 6000 proinsulin molecules per second. Ordinarily, nascent proinsulin entering the ER rapidly folds via the formation of three evolutionarily conserved disulfide bonds (B7–A7, B19–A20, and A6–A11). A modest amount of proinsulin misfolding, including both intramolecular disulfide mispairing and intermolecular disulfide‐linked protein complexes, is a natural by‐product of proinsulin biosynthesis, as is the case for many proteins. The steady‐state level of misfolded proinsulin—a potential ER stressor—is linked to (1) production rate, (2) ER environment, (3) presence or absence of naturally occurring (mutational) defects in proinsulin, and (4) clearance of misfolded proinsulin molecules. Accumulation of misfolded proinsulin beyond a certain threshold begins to interfere with the normal intracellular transport of bystander proinsulin, leading to diminished insulin production and hyperglycemia, as well as exacerbating ER stress. This is most obvious in mutant INS gene–induced Diabetes of Youth (MIDY; an autosomal dominant disease) but also likely to occur in type 2 diabetes owing to dysregulation in proinsulin synthesis, ER folding environment, or clearance.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143748/1/nyas13531.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/143748/2/nyas13531_am.pd

Electric field effects on proteins Novel perspectives on food and potential health implications

Electric fields (EF) technologies have been establishing a solid position in emergent food processing and have seen as serious alternatives to traditional thermal processing. During the last decades, research has been devoted to elucidation of technological and safety issues but also fundamental aspects related with interaction of electric fields (EF) with important macromolecules, such as proteins. Proteins are building blocks for the development of functional networks that can encompass health benefits (i.e. nutritional and bioactive properties) but may be also linked with adverse effects such as neurodegenerative diseases (amyloid fibrils) and immunological responses. The biological function of a protein depends on its tridimensional structure/conformation, and latest research evidences that EF can promote disturbances on protein conformation, change their unfolding mechanisms, aggregation and interaction patterns. This review aims at bringing together these recent findings as well as providing novel perspectives about how EF can shape the behavior of proteins towards the development of innovative foods, aiming at consumers health and wellbeing.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 and UIDB 50006/2020 with funding from FCT/ MCTES through national funds, BioTecNorte operation (NORTE-01- 0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. This work was also supported by the projects AlleRiskAssess – PTDC/BAA-AGR/31720/2017 and NORTE-01-0145-FEDER-031720. Zita Avelar acknowledge the Foundation for Science and Technology (FCT) for its fellowship SFRH/BD/146347/2019info:eu-repo/semantics/publishedVersio

Experimental Polymer Mechanochemistry and its Interpretational Frameworks

Polymer mechanochemistry is an emerging field at the interface of chemistry, materials science, physics and engineering. It aims at understanding and exploiting unique reactivities of polymer chains confined to highly non-equilibrium stretched geometries by interactions with their surroundings. Macromolecular chains or their segments become stretched in bulk polymers under mechanical loads or when polymer solutions are sonicated or flow rapidly through abrupt contractions. An increasing amount of empirical data suggests that mechanochemical phenomena are widespread wherever polymers are used. In the past decade, empirical mechanochemistry has progressed enormously, from studying fragmentations of commodity polymers by simple backbone homolysis to demonstrations of self-strengthening and stress-reporting materials and mechanochemical cascades using purposefully designed monomers. This progress has not yet been matched by the development of conceptual frameworks within which to rationalize, systematize and generalize empirical mechanochemical observations. As a result, mechanistic and/or quantitative understanding of mechanochemical phenomena remains, with few exceptions, tentative. In this review we aim at systematizing reported macroscopic manifestations of polymer mechanochemistry, and critically assessing the interpretational framework that underlies their molecular rationalizations from a physical chemist's perspective. We propose a hierarchy of mechanochemical phenomena which may guide the development of multiscale models of mechanochemical reactivity to match the breadth and utility of the Eyring equation of chemical kinetics. We discuss the limitations of the approaches to quantifying and validating mechanochemical reactivity, with particular focus on sonicated polymer solutions, in order to identify outstanding questions that need to be solved for polymer mechanochemistry to become a rigorous, quantitative field. We conclude by proposing 7 problems whose solution may have a disproportionate impact on the development of polymer mechanochemistry

Protein stability in shear flow

© 2010 Dr. Innocent Berbelle BekardGiven that globular proteins show a strong conformation-function relationship, the stability of a native protein structure is essential for its function. Aberrant proteins, resulting from structural instabilities in native protein conformations, and consequent aggregation, evolve a gain-of-function pathogenesis which has serious implications in industry and medicine. Therefore, it is important to appreciate the key factors that perturb the solution conformation of protein systems leading to aggregation. Considering the fact that proteins generally function in solution form, and those solutions have an inherent tendency to flow, knowledge of the stability of protein solutions in shear flow is essential. This thesis employs a combination of spectroscopic and microscopic techniques to study the conformational dynamics and morphological transformations of bulk peptide/polypeptide solutions in both uniform and heterogeneous velocity gradients. Preliminary studies in this thesis demonstrate that protein denaturation and subsequent aggregation can be probed using intrinsic protein fluorescence. The induction of protein aggregation was found to be greatly enhanced in heterogeneous flow regimes. Studies in a well defined flow field, Couette flow, revealed that the hydrodynamic stress generated in such flow regimes induce the unfolding of the helical segments of natively folded insulin; a prerequisite for aggregation and amyloid fibril formation. Further analysis of the shear-effect on α-helical conformations was performed using the homopolypeptide poly-L-lysine as a model protein system. The results reveal that the shear-induced unfolding of α-helical segments depends on both the shear rate and the duration of its application. An assessment of the chain-length-dependence of this phenomenon revealed that, contrary to classical theory, the strain in a given flow field varies inversely with the chain-length of α-helical poly-L-lysine. Collectively, the results provide new insight into existing theories in polymer physics. More importantly, it provides quantitative information on the conformational dynamics of peptide/polypeptide solutions in shear flow. This report is relevant to quality control measures during the commercial isolation and purification of protein products, and might help explain the role of shear stress, originating from pulsatile blood flow, in protein misfolding diseases and vascular disorders

α-Helix unfolding in simple shear flow

The unfolding dynamics of the α-helical poly-L-lysine (α-PLL) in Couette flow is reported. Real-time circular dichroism measurements for a range of molecular weights and shear rates have been made. The PLL molecules show a time- and shear rate-dependent unfolding in simple shear flow with a critical strain ([small gamma, Greek, dot above]tc) value of [similar]105. This strain value is found to be independent of the chain-length of the α-helices. The extent of unfolding is less pronounced with increasing molecular weight (M) for a given strain, showing a linear dependence of the remaining helix, α, on M: α ≈ M. Furthermore, the helix content, α, is found to show a power law dependence with strain: α ≈ ([small gamma, Greek, dot above]t)−1/2. A shear-induced rapid unfolding of short chain α-PLL molecules in the flow field occurs. The shear-stability of the larger molecular weights is due to the cohesive forces stabilizing the helix, combined with the associated hydrodynamic screening of helical segments from the full effect of the drag in the flow field. The data are compared with recent molecular dynamics simulations of the dynamics of dilute polymer solutions in shear flow and scaling arguments are used to interpret the trends in the data.