Effect Of Protein Oxidation Research Articles

Effect of protein oxidation on the stability of peanut beverage

Protein oxidation of peanut beverage and their stability during the storage were investigated. To further investigate the relationship between protein oxidation and peanut beverage stability, peanut protein isolate (PPI) was oxidized by peroxyl radicals derived from 2,2ʹ-azobis (2-amidinopropane) dihydrochloride (AAPH), and the emulsion properties stabilized by oxidized PPI were evaluated. During the storage, protein oxidation happened in the peanut beverage, accompanied by deteriorating their stability. Low storage temperature would lighten the oxidation extent and the peanut beverage instability. High roasting pretreatment of peanut kernels before making peanut beverage would enhance the protein oxidation. Emulsion stabilized by oxidized PPI had larger mean droplet size and lower surface charge. Microstructure of PPI stabilizing emulsion showed that emulsions stabilized by PPI of overoxidation underwent severe droplet aggregation during storage. Protein oxidation was an important factor influencing stability during peanut beverage storage.

Relationship between N-nitrosodiethylamine formation and protein oxidation in pork protein extracts

The relationship between protein oxidation and N-nitrosodiethylamine (NDEA) formation was assessed. Packaged fresh minced pork was stored at 2 ± 1 °C for 0, 4, 7, and 10 days. Myofibrillar protein (MP), sarcoplasmic protein (SP), and muscle homogenate were obtained from the stored minced pork and allowed to react with sodium nitrite at 80 °C for 1 h. The relationship between NDEA formation and indexes of protein oxidation was assessed by principal component analysis. The formation of NDEA in meat was correlated with protein and lipid oxidation. Lipid oxidation promoted the formation of NDEA and was positively correlated with protein oxidation. Carbonyl compounds from oxidized MP and free amines from dissociated SP promoted NDEA formation. Therefore, the effect of protein oxidation on NDEA formation depends on the type of protein and its oxidation products.

The effect of protein oxidation on hydration and water-binding in pork packaged in an oxygen-enriched atmosphere

This study investigated the in situ oxidative process of myofibrillar proteins in boneless pork loin chops (Longissimus lumborum) packaged in an oxygen-enriched atmosphere (HiOx: 80% O2/20% CO2), an air-permeable polyvinylchloride (PVC) overwrap, or a partial vacuum (VP) throughout display at 2°C for up to 14, 7, and 21days, respectively. Samples stored in HiOx were susceptible to lipid (TBARS) and protein (carbonyls, sulfhydryls, and aggregation) oxidation, while samples in PVC and VP showed lesser oxidative changes. Water-holding capacity of raw muscle decreased (P<0.05) when stored in HiOx but not in PVC and VP. Upon salt and phosphate brine marination, HiOx and PVC muscle samples had improved hydration capacity during display compared with non-stored control, but display generally decreased hydration of VP samples. The result was in agreement with myofibril structural changes. Despite the enhanced hydration, HiOx muscle was least capable of withholding moisture upon cooking.

Effects of Oxidation on Protein-Nanoparticle Interactions

Aims: Upon entrance into the blood stream most nanoparticles bind to an array of proteins forming a “protein corona”. Fibrinogen is the second most abundant blood protein and has been reported to bind to a variety of nanoparticles including metal oxides, polymeric nanoparticles and carbon nanotubes. Study Design: Study the effects of oxidation on the binding interactions between human serum fibrinogen and magnetic iron (III) oxide nanoparticles. Place and Duration of Study: Department of Chemistry, College of St. Benedict, 37 South College Avenue, St. Joseph, MN 56374, U.S.A., between June 2011 and May 2012. Methodology: Spectroscopic techniques (UV-Vis, IR, fluorescence, and circular dichroism) were used to study the binding interactions of magnetic nanoparticles with human serum fibrinogen and the effects of protein oxidation on its binding affinity. Results: Magnetic nanoparticles (MNP) formed stable complex with fibrinogen under physiological conditions. The binding constants (Ka) were determined as 1.91 (± 0.14) x10 M and 1.06 (± 0.09) x10 M at 300 K and 310 K respectively. The secondary structure of the protein was slightly affected by the formation of fibrinogen-MNP complex. When the protein was oxidized with metal catalyzed oxidation (MCO) system, significant changes in the protein structure was detected leading to decreased binding affinity for Original Research Article British Journal of Pharmaceutical Research, 4(2):172-185, 2014 173 MNP. Conclusion: Metal catalyzed oxidation of fibrinogen significantly affects its binding interactions with magnetic iron (III) oxide nanoparticles.

Interfacial Mussel Proteins Characterization with the Surface Forces Apparatus

The biomaterial that mussels produce to fix themselves to their substrate has become a model system for gleaming insights into effective underwater adhesion. These superficially simple animals are capable of fastening robust organic attachments to chemically diverse substrates such as ceramics, metal oxides, polymers and silicate clays. Proteins from this adhesive material have been purified and characterized resulting in a family of molecules with unusual charges, compositions and post-transnational modifications. One of these modifications, dihydroxyphenylalanine (DOPA) as gained traction for being found in a multitude of animal adhesive systems as well as having been shown to have impressive work of adhesion values in simple systems. Proteins from the mussel attachment plaque that are simultaneously found at the interface of the substrate and contain unusually high DOPA content were characterized by the Surfaces Forces Apparatus. This instrument allows for interactions between surfaces and deposited thin films to be measured. The force distance profiles calculated are sensitive to angstrom resolution and pN forces.In this talk the results of characterizing interfacial mussel foot proteins by with the surfaces forces apparatus will be discussed. The effects on adhesion from solution conditions- especially with regard to pH, protein-protein interactions, effects of protein oxidation and reduction, as well as the potential utility of borate protection are shown in a quantitative way.

Effect of protein oxidation on the in vitro digestibility of soy protein isolate

Soy protein isolate (SPI) was modified by 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH) oxidation pretreatment, and the in vitro digestibility of oxidised SPI was investigated. Results indicated that oxidation induced amino acid modification. The amount of most amino acids decreased, accompanied by decreasing digestive proteolysis susceptibility. Peptide size distribution implied that oxidation generated protein aggregates that could not be degraded by pepsin, but could be digested by pancreatin. Oxidation induced a maximum of 16.6% and 14.6% loss, respectively, for free essential and free total amino acid in the digests of oxidised SPI. Antioxidant activities evaluation of oxygen radical absorbance capacity (ORAC) value and DPPH scavenging activity showed that oxidation deteriorated the antioxidant activities of the digests from oxidised SPI.

Effect of Protein Oxidation on the Conformational Properties of Peanut Protein Isolate

Peanut protein isolate (PPI) was oxidized by peroxyl radicals derived from 2,2′‐azobis (2‐amidinopropane) dihydrochloride (AAPH), and the conformational properties of oxidized PPI were investigated. Oxidation of PPI resulted in gradual carbonyl generation and free sulfydryl group degradation. The analysis of the maximum emission wavelength indicated change in the tertiary conformation of PPI after oxidation. Lower level oxidation could generate soluble protein aggregates with more flexible structure, while higher level oxidation would induce the formation of insoluble aggregates. Result from dynamic light scattering (DLS) and protein solubility showed that protein aggregation was correlated with protein surface hydrophobicity, indicating that protein oxidation and heat treatment could induce protein aggregation, leading to PPI conformational changes.

Methionine Oxidation Enhances κ-Casein Amyloid Fibril Formation

The effects of protein oxidation, for example of methionine residues, are linked to many diseases, including those of protein misfolding, such as Alzheimer's disease. Protein misfolding diseases are characterized by the accumulation of insoluble proteinaceous aggregates comprised mainly of amyloid fibrils. Amyloid-containing bodies known as corpora amylacea (CA) are also found in mammary secretory tissue, where their presence slows milk flow. The major milk protein κ-casein readily forms amyloid fibrils under physiological conditions. Milk exists in an extracellular oxidizing environment. Accordingly, the two methionine residues in κ-casein (Met(95) and Met(106)) were selectively oxidized and the effects on the fibril-forming propensity, cellular toxicity, chaperone ability, and structure of κ-casein were determined. Oxidation resulted in an increase in the rate of fibril formation and a greater level of cellular toxicity. β-Casein, which inhibits κ-casein fibril formation in vitro, was less effective at suppressing fibril formation of oxidized κ-casein. The ability of κ-casein to prevent the amorphous aggregation of target proteins was slightly enhanced upon methionine oxidation, which may arise from the protein's greater exposed surface hydrophobicity. No significant changes to κ-casein's intrinsically disordered structure occurred upon oxidation. The enhanced rate of fibril formation of oxidized κ-casein, coupled with the reduced chaperone ability of β-casein to prevent this aggregation, may affect casein-casein interaction within the casein micelle and thereby promote κ-casein aggregation and contribute to the formation of CA.

Effects of Protein Oxidation on the Structure and Stability of Model Discoidal High-Density Lipoproteins

High-density lipoproteins (HDLs) prevent atherosclerosis by removing cholesterol from macrophages and by providing antioxidants for low-density lipoproteins. Oxidation of HDLs affects their functions via the complex mechanisms that involve multiple protein and lipid modifications. To differentiate between the roles of oxidative modifications in HDL proteins and lipids, we analyzed the effects of selective protein oxidation by hypochlorite (HOCl) on the structure, stability, and remodeling of discoidal HDLs reconstituted from human apolipoproteins (A-I, A-II, or C-I) and phosphatidylcholines. Gel electrophoresis and electron microscopy revealed that, at ambient temperatures, protein oxidation in discoidal complexes promotes their remodeling into larger and smaller particles. Thermal denaturation monitored by far-UV circular dichroism and light scattering in melting and kinetic experiments shows that protein oxidation destabilizes discoidal lipoproteins and accelerates protein unfolding, dissociation, and lipoprotein fusion. This is likely due to the reduced affinity of the protein for lipid resulting from oxidation of Met and aromatic residues in the lipid-binding faces of amphipathic alpha-helices and to apolipoprotein cross-linking into dimers and trimers on the particle surface. We conclude that protein oxidation destabilizes HDL disk assembly and accelerates its remodeling and fusion. This result, which is not limited to model discoidal but also extends to plasma spherical HDL, helps explain the complex effects of oxidation on plasma lipoproteins.