Characterization Of Protein Fractions Research Articles

“Antioxidant activity and characterization of protein fractions and hydrolysates from normal and quality protein maize kernels”

Maize is the main crop cultivated worldwide with more than 1 billion metric tons produced annually and is one of the most relevant sources of protein for human consumption in developing countries. Proteins and peptides isolated from maize exert relevant antioxidant activity which is increased by enzymatic hydrolysis. However, there is limited information about the antioxidant potential of proteins isolated from Quality Protein Maize (QPM) varieties and their hydrolysates. The aim of this research was to determine the differences in protein profile and antioxidant activity of protein fractions and hydrolysates between a hybrid white maize (Asgrow 773) and a QPM variety (CML-502). The biophysical evaluation and the total protein quantification by Kjeldahl and fractions by ninhydrin were consistent with the changes due to the breeding process of the QPM material. The antioxidant potential of the hydrolysates obtained from albumins and globulins had a 3-fold increase in both maize varieties. The prolamins hydrolysates presented an increase of 7-fold for the normal variety and 2-fold for the QPM variety. The results of this research allow indicate that the QPM varieties are a source of antioxidant peptides and promising candidates in the search for proteins and peptides with other bioactivities.

Characterization of protein fractions and antioxidant activity of Chia seeds (Salvia hispanica L.)

Chia seed (Salvia hispanica L.) is an annual herbaceous plant categorized under Lamiaceae family. Chia seeds were investigated as a source of proteins and natural antioxidants. It is a potential alternative source of high quality protein, fats, carbohydrates, high dietary fibre, vitamins and mineral elements. The objective of this study was to evaluate chia seed from protein content and antioxidant acivity and highlight the quality of this pseudocereal. A crude protein, moisture content, content of protein fractions, total antioxidant capacity (TAC) and superoxide dismutase activity of chia seeds and food products containing chia seeds were determined. The protein content of chia seeds ranged from 2.9% to 4.6% dry matter from that albumins and globulins ranged from 54.6% to 62.8%. Chia is poor in a prolamines (<15%). Various chia seeds showed differences in their SOD activity and exhibited the high antiradical activity against 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS). The highest antioxidant capacity was found in sample chia seeds from Bolivia (1.46 mM TEAC.g-1 in the dry matter) and the lowest values of antioxidant activity was estimated in sample chia seeds from Argentina (1.05 mM TEAC.g-1 in the dry matter). The highest SOD activity was determined in sample chia from Argentina (2191.8 U.g-1 in the dry matter). The lowest SOD activity was found in sample chia-bio from Argentina (754.0 U.g-1 in the dry matter.). It makes them potentially suitable for use in the gluten-free diet of coeliac people and it can be used as a potential ingredient in health food because of its high antioxidant activity.

Extraction and characterisation of protein fractions from five insect species

Tenebrio molitor, Zophobas morio, Alphitobius diaperinus, Acheta domesticus and Blaptica dubia were evaluated for their potential as a future protein source. Crude protein content ranged from 19% to 22% (Dumas analysis). Essential amino acid levels in all insect species were comparable with soybean proteins, but lower than for casein. After aqueous extraction, next to a fat fraction, a supernatant, pellet, and residue were obtained, containing 17–23%, 33–39%, 31–47% of total protein, respectively. At 3% (w/v), supernatant fractions did not form stable foams and gels at pH 3, 5, 7, and 10, except for gelation for A. domesticus at pH 7. At 30% w/v, gels at pH 7 and pH 10 were formed, but not at pH 3 and pH 5. In conclusion, the insect species studied have potential to be used in foods due to: (1) absolute protein levels; (2) protein quality; (3) ability to form gels.

Extraction and characterization of protein fractions from Australian canola meals

Canola proteins were sequentially extracted from four Australian canola meals of different species and two industrial meal samples, according to Osborne method (OSB), based on their solubilities in water, 5% NaCl, 0.1 M NaOH and 70% ethanol respectively. These extracts were then compared to the glutelin fraction obtained by direct alkaline extraction method (DIR) in terms of protein yield, recovery, electrophoretic profile, and residual antinutritional components. The OSB method was found to be more effective for protein extraction which resulted in higher cumulative protein yield and recovery of water-soluble protein fractions, although the DIR method produced a glutelin fraction of higher protein content. Phenolic compounds were observed in all the extracted protein fractions although sinapine, the major phenolic compound in canola, was present only in the albumin fractions. The glucosinolate content of all extracts was below the detection limit of the method employed (< 3 μmol/g). While the electrophoretic profiles of all four OSB fractions were largely different, the DIR fraction was very similar to the glutelins obtained from the OSB method. Isoelectric focusing revealed that many of the proteins in the canola varieties ranged in pI between pH4.6 and 8.3.

Effect of storage proteins on pasting properties and microstructure of Thai rice

This study investigated the influences of rice storage proteins, in relation to amylose content, on pasting properties of newly harvested Thai rice. The polished rice cultivars investigated included waxy rice SPT1, which contained 1.3% amylose and 8.3% protein; and non-waxy rice, namely PTT1 and LPT123, which contained 14.1% and 28.6% amylose, and 6.7% and 9.6% protein, respectively. The characteristics of protein fractions were altered by accelerated aging at 60 °C and 70% relative humidity (RH) for 5 days, and/or by alkali deproteinisation and cysteine addition during Rapid Visco Analyser (RVA) pasting characterisation. Accelerated aging, deproteinisation and the reduction of disulfide bonds changed the RVA pasting curves of all Thai rice cultivars, particularly the waxy one (p < 0.05). This study has quantified the contribution of protein in relation to amylose on the RVA pasting profiles and demonstrated that protein and starch were in separated phases after heating. The continuity of the protein network in cooked non-waxy rice grains observed under confocal laser scanning microscopy (CLSM) indicated bi-continuous structure of starch and protein phases.

Isolation and characterization of protein fractions from deoiled rice bran

Rice bran contains underutilised protein materials. Sequential extraction of rice bran protein (RBP) from defatted rice bran was conducted based on the differences in their solubility. Three extraction methods were investigated. Method 1 involved the isoelectric and acetone precipitation using water, 50 g kg−1 NaCl, 0.02 mol L−1 NaOH and 70% ethanol as extracting solvents for albumin (pH 4.1), globulin (pH 4.3), glutelin (pH 4.8) and prolamin, respectively. Method 2 adopted dialysis and sequential extraction was carried out with 20 g kg−1 NaCl, 70% ethanol, 0.1 mol L−1 acetic acid and 0.1 mol L−1 NaOH solution as extracting solvents. Method 3 combined dialysis, isoelectric and acetone precipitation for the extraction. Based on the yields and data obtained from sodium dodecyl sulphate polyacrylamide gel electrophoresis, size-exclusion chromatography and differential scanning calorimetry, method 3 was chosen for the isolation and characterization of RBPs. Rice bran protein fraction (RBPF)—albumin, globulin, glutelin and prolamin were obtained in good yields. Denaturation temperature and enthalpy values of denaturation of RBPF vary. Highest phytate content was found in albumin and lowest in prolamin. The highest antioxidative and hemagglutinating activities were observed in albumin.

Characterization of protein fractions and amino acids in ensiled alfalfa treated with different chemical additives

Formic acid, formaldehyde, tannic acid or mixtures of two were studied on their effects on ensiled alfalfa ( Medicago sativa L.) amino acids and N fractions by the Cornell Net Carbohydrate and Protein System (CNCPS). The alfalfa forage was a second cut and was wilted to a mean over-dry dry matter (DM) content of 330 g/kg. All silages were prepared as mini-silos using 100 ml polypropylene centrifuge tubes (50 g) on a small laboratory-scale, with the additives added in 20 ml aliquots/kg herbage fresh weight (FW). After 35 d of ensiling, most of forage true protein was converted to fraction A and all of the added additives reduced fraction A content in the ensiled forages (P<0.05). The content of fraction B 1 in all of the additive-treated silages was higher (P<0.05) than that in control silage. Large proportions of true protein in the tannic acid/formaldehyde- and formic acid/formaldehyde-treated silages were fractions B 2 and B 3, respectively. No difference was observed on fraction C content between the control silage and silages treated with additives except for the formaldehyde or tannic acid-treated silages. Amino acids were well preserved in additive-treated silages compared with the control silage. Concentration of total amino acid was higher in formic acid-treated silages than that in the control and the other additive-treated silages (P<0.05). The pattern of changes in individual amino acid in all of the silages indicated that branched chain amino acids and methionine were relatively well preserved during fermentation but the basic and acidic amino acids were not.

Characterization of Protein Fractions from Immature Alaska Walleye Pollock (Theragra chalcogramma) Roe

There are good markets for mature pollock roe; however, immature pollock roe is underutilized. The physical and nutritional properties of immature pollock roe (IPR) have not been reported, which limits its potential use as a food ingredient. The objective of this study was to evaluate the physical and nutritional properties of immature pollock roe and soluble and insoluble protein powders made from the immature roe. IPR samples were obtained during the spring pollock harvest from a seafood processing plant in Kodiak, Alaska. Soluble (SP) and insoluble protein (IP) fractions were produced by heating IPR, separating by centrifugation and freeze drying. The protein contents of freeze-dried IPR, SP, and IP were 81.7%, 63.2%, and 83.0%, respectively. The amino acid contents of IPR and IP were similar except for isoleucine and valine. However, the amino acid contents of IPR and IP were different from values for SP. Lipid contents of IPR, SP, and IP were 9.2%, 9.3%, and 11.1%, respectively. Palmitic acid (C16:0; 21.2%), DHA (C22:6omega3; 21.2%), and EPA (C20:5omega3; 19.0%) were the 3 most abundant fatty acids in fresh IPR. Fat adsorption capacity value for SP was significantly higher than IPR and IP (P < 0.05). SDS electrophoresis indicated a major protein band with molecular weight of 103 KDa in all samples. Results indicate that IPR can be utilized to make a number of unique food ingredients with good nutritional characteristics and functional properties.

Characterization of Protein Fractions from Bt-Transgenic and Non-transgenic Maize Varieties Using Perfusion and Monolithic RP-HPLC. Maize Differentiation by Multivariate Analysis

Protein fractions from transgenic Bt and non-transgenic maize varieties, extracted by the Osborne solvent fraction procedure, were characterized for the first time by perfusion and monolithic RP-HPLC in very short analysis times. Albumins and globulins from different transgenic Bt maizes as well as from their non-transgenic isogenic varieties were eluted in four peaks using perfusion RP-HPLC, whereas prolamins and glutelins were separated in seven peaks. Monolithic RP-HPLC enabled the separation of maize proteins in a large number of peaks showing 6 and 10 main peaks for albumins and globulins, respectively. Prolamins migrated at retention times higher than 5 min as seven peaks, whereas glutelins were separated in three main peaks appearing at retention times higher than 6.0 min. Moreover, chromatograms of the whole protein extracts showed 8 and 11 components for perfusion and monolithic RP-HPLC, respectively. A comparison of the chromatograms of the whole protein extracts relative to transgenic and non-transgenic varieties evidenced quantitative differences on the percentages of area, mainly for peaks 2 and 3 by perfusion RP-HPLC and for peaks 3 and 7 by monolithic RP-HPLC. A discriminant analysis based on these proteic profiles was carried out to classify and predict transgenic Bt maize lines, achieving 100% correct classification using perfusion RP-HPLC.

Characterization of Protein Fractions in Fresh, Wilted, and Ensiled Alfalfa

Fresh, wilted, and ensiled alfalfas were homogenized; the proteins were fractioned into total, soluble proteins precipitated at 40% ammonium sulfate concentration (fraction 2), soluble proteins recovered after extraction of fraction 2 (fraction 2B), and chloroplast membrane proteins (fraction 3). The fractions were analyzed by gel electrophoresis and assayed for sulfhydryl and disulfide content, dodecyl sulfate-binding capacity, and zeta potential. Wilting of alfalfa caused the loss of high molecular mass proteins, 49-kDa proteins of fraction 2 and 18- and 60-kDa proteins of fraction 3. Wilting alone did not affect proteins of fraction 2B but ensiling resulted in loss of five bands between molecular mass of 15 and 25 kDa. Ensiling wilted alfalfa resulted in loss of all proteins except small quantities of 22-, 33-, and 36-kDa proteins of fraction 2 and 15-, 28-, and 60-kDa proteins of fraction 3. Sulfhydryl and disulfides were increased during wilting and decreased by the ensiling process. Dodecyl sulfate-binding capacity was increased by ensiling, indicating that proteins in silage have a faster rate of enzymatic digestion. Soluble proteins had higher zeta potential than chloroplast membranes. Forage proteins surviving ensiling were albumins of fraction 2B and chloroplast membranes. These results indicate that alfalfa silage proteins are highly degradable in the rumen.

Changes in insulin-like growth factors I and II and their binding protein after a single intramuscular injection of growth hormone.

The concentrations of insulin-like growth factors I and II (IGF-I and IGF-II) and their binding proteins in serum were measured in 10 GH-deficient patients before and after a single 6-IU injection of GH. Serum IGF-I concentrations were initially low, increased significantly by 8 and 24 h, and decreased to pretreatment levels 48 and 72 h after GH administration. Serum IGF-II concentrations also were low initially and did not increase by 8 and 24 h, but were, however, significantly higher 48 and 72 h after GH administration. In GH-deficient patients before GH administration, binding of IGF-I or IGF-II to serum proteins was restricted primarily to proteins of 50K mol wt. Little or no binding to proteins of 150,000 mol wt was found. By 8 and 24 h after GH injection, IGF-I, but not IGF-II, bound primarily to a protein(s) of 150K mol wt, as in normal subjects. IGF-II remained bound to a 50K mol wt protein. By 48 and 72 h after administering GH, however, the binding pattern was reversed, and IGF-II, but not IGF-I, bound predominantly to a protein(s) of 150K mol wt. Our data demonstrate both a temporal dissociation in the responses of IGF-I and IGF-II to GH and a similar temporal dissociation in the binding of IGF-I and IGF-II to the large mol wt (150K) binding protein. This dissociation, particularly the latter, may provide a means for better characterization of protein fractions in binding IGF, particularly in terms of specificity.

Characteristics of Protein Fractions Isolated from the Fat/Plasma Interface of Homogenized Milk

Summary The technique employed to isolate the proteins of the fat-globule membrane of homogenized milk was based on a procedure described by Herald and Brunner (4) for isolating the membrane proteins of nonhomogenized milk. Since homogenization results in the alteration of the components constituting the fat/plasma interface in milk, their methods were modified and extended to include a fractionation for milk proteins other than the normal membrane-proteins. The insoluble membrane-protein, constituting a portion of the normal membrane, was isolated from the homogenized fat-globule membrane. This reddish-brown fraction remained, at least in part, with the fat globule following homogenization. The soluble membrane-protein of the nonhomogenized fat globule was recovered from preparations of the membrane of homogenized milk. A portion of this protein fraction appeared to be associated electrophoretically with the α -casein oriented at the fat/plasma interface. The remaining portion was recovered from the membrane as an unassociated protein fraction. An atypical casein fraction, in which the alpha component appeared to be associated with the normally occurring soluble membrane-protein (glycoprotein) was isolated from the resurfaced fat-globule. The association occurred when milk was homogenized or when artificial systems containing whole casein, or α -casein, soluble membrane-protein, and milk fat were homogenized. This phenomenon was characterized by a trailing peak on the α -casein peak in the electrophoretic patterns. When considered as a part of the alpha peak, unusually high α- β -casein ratios were obtained.An accompanying decrease in the electrophoretic mobility of α-casein was noted. The presence of a heat-coagulable protein fraction, presumed to be whey proteins but not identified conclusively, was also noted.