In vitro pepsin resistance of proteins: Effect of non-reduced SDS-PAGE analysis on fragment observation

Increased chaperone activity of human α‌B-crystallin with incomplete oxidation as a new defense mechanism against oxidative stress

Previous research has shown that production of the high levels of oxidants overwhelms the body's antioxidant defense system during diabetes mellitus. Under this circumstance, ocular lens proteins are one of the main molecular targets for oxidative damage. In the present study, the individual effect of partial and extensive oxidation on the structure and function of human αB-crystallin was investigated using electrophoresis and various spectroscopic methods. The results of our study suggested that widespread oxidation causes loss of the chaperone activity of this protein, while partial oxidation significantly enhances this activity. Our studies also suggested that partial and extensive oxidation induces the formation of different structures in this protein. In fact, the chaperone-active and chaperone-inactive states of this protein are respectively associated with a minor and extensive structural alteration. Moreover, the oligomeric size distribution shows an inverse relationship with the chaperone activity of this protein. Increasing the chaperone activity of this protein during partial oxidation may be a natural defense mechanism to overcome the damages caused by oxidative stress, especially in diabetes and other pathological diseases.

Scientific Opinion on development needs for the allergenicity and protein safety assessment of food and feed products derived from biotechnology

This Scientific Opinion addresses the formulation of specific development needs, including research requirements for allergenicity assessment and protein safety, in general, which is urgently needed in a world that demands more sustainable food systems. Current allergenicity risk assessment strategies are based on the principles and guidelines of the Codex Alimentarius for the safety assessment of foods derived from 'modern' biotechnology initially published in 2003. The core approach for the safety assessment is based on a 'weight-of-evidence' approach because no single piece of information or experimental method provides sufficient evidence to predict allergenicity. Although the Codex Alimentarius and EFSA guidance documents successfully addressed allergenicity assessments of single/stacked event GM applications, experience gained and new developments in the field call for a modernisation of some key elements of the risk assessment. These should include the consideration of clinical relevance, route of exposure and potential threshold values of food allergens, the update of in silico tools used with more targeted databases and better integration and standardisation of test materials and in vitro/in vivo protocols. Furthermore, more complex future products will likely challenge the overall practical implementation of current guidelines, which were mainly targeted to assess a few newly expressed proteins. Therefore, it is timely to review and clarify the main purpose of the allergenicity risk assessment and the vital role it plays in protecting consumers' health. A roadmap to (re)define the allergenicity safety objectives and risk assessment needs will be required to inform a series of key questions for risk assessors and risk managers such as 'what is the purpose of the allergenicity risk assessment?' or 'what level of confidence is necessary for the predictions?'.

Effect of processing on in vitro digestibility (IVPD) of food proteins

Proteins are important macronutrients for the human body to grow and function throughout life. Although proteins are found in most foods, their very dissimilar digestibility must be taking into consideration when addressing the nutritional composition of a diet. This review presents a comprehensive summary of the in vitro digestibility of proteins from plants, milk, muscle, and egg. It is evident from this work that protein digestibility greatly varies among foods, this variability being dependent not only upon the protein source, but also the food matrix and the molecular interactions between proteins and other food components (food formulation), as well as the conditions during food processing and storage. Different approaches have been applied to assess in vitro protein digestibility (IVPD), varying in both the enzyme assay and quantification method used. In general, animal proteins tend to show higher IVPD. Harsh technological treatments tend to reduce IVPD, except for plant proteins, in which thermal degradation of anti-nutritional compounds results in improved IVPD. However, in order to improve the current knowledge about protein digestibility there is a vital need for understanding dependency on a protein source, molecular interaction, processing and formulation and relationships between. Such knowledge can be used to develop new food products with enhanced protein bioaccessibility.

Crystal structures of serum albumins from domesticated ruminants and their complexes with 3,5-diiodosalicylic acid

Serum albumin (SA) is the most abundant protein in plasma and is the main transporter of molecules in the circulatory system of all vertebrates, with applications in medicine, the pharmaceutical industry and molecular biology. It is known that albumins from different organisms vary in sequence; thus, it is important to know the impact of the amino-acid sequence on the three-dimensional structure and ligand-binding properties. Here, crystal structures of ovine (OSA) and caprine (CSA) serum albumins, isolated from sheep and goat blood, are described, as well those of their complexes with 3,5-diiodosalicylic acid (DIS): OSA-DIS (2.20 Å resolution) and CSA-DIS (1.78 Å resolution). The ligand-free OSA structure was determined in the trigonal space group P3221 at 2.30 Å resolution, while that of CSA in the orthorhombic space group P212121 was determined at 1.94 Å resolution. Both albumins are also capable of crystallizing in the triclinic space group P1, giving isostructural crystals that diffract to around 2.5 Å resolution. A comparison of OSA and CSA with the closely related bovine serum albumin (BSA) shows both similarities and differences in the distribution of DIS binding sites. The investigated serum albumins from domesticated ruminants in their complexes with DIS are also compared with the analogous structures of equine and human serum albumins (ESA-DIS and HSA-DIS). Surprisingly, despite 98% sequence similarity, OSA binds only two molecules of DIS, whereas CSA binds six molecules of this ligand. Moreover, the binding of DIS to OSA and CSA introduced changes in the overall architecture of the proteins, causing not only different conformations of the amino-acid side chains in the binding pockets, but also a significant shift of the whole helices, changing the volume of the binding cavities.

Effect of molecular weight and ratio of poly ethylene glycols' derivatives in combination with trehalose on stability of freeze-dried IgG

The influence of poly ethylene glycol (PEG) at different molecular weights (MWs) and ratios was studied on the stability of freeze-dried immune globulin G (IgG). PEGs (600-4000 Dalton) at concentrations of 0.5 and 5% W/V were applied in the presence of 40 and 60% W/W of trehalose to prepare freeze-dried IgG formulations. Size-exclusion chromatography, infra-red spectroscopy, differential scanning calorimeter, and gel electrophoresis were performed to characterize lyophilized samples. Pure IgG demonstrated the highest aggregation of 5.77 ± 0.10% after process and 12.66 ± 0.50% as well as 44.69 ± 0.50% upon 1 and 2 months of storage at 45 °C, respectively. 5% W/V of PEGs 4000 in combination with 40% W/W trehalose, significantly suppressed aggregation, 0.05 ± 0.01%, with minimum aggregation rate constant of 0.32 (1/month). The integrity of IgG molecules and secondary conformation were properly preserved in all formulations comparing native IgG. It could be concluded that appropriate concentration and MW of PEGs, prominently augmented stabilizing effect of trehalose on freeze-dried antibody through inserting additional supportive mechanisms of actions.