Content Amino Research Articles

Investigation of the Maillard Reaction between Polysaccharides and Proteins from Longan Pulp and the Improvement in Activities.

The purpose of this study was to investigate the Maillard reaction between polysaccharides and proteins from longan pulp and the effects of reaction on their in vitro activities. The polysaccharide-protein mixtures of fresh longan pulp (LPPMs) were co-prepared by an alkali extraction–acid precipitation method. They were then dry-heated under controlled conditions for monitoring the characterization of the Maillard reaction by the measurement of the free amino group content, ultraviolet-visible spectrum, Fourier transform infrared spectrum and molecular weight distribution. All the physicochemical analyses indicated the development of the Maillard reaction between polysaccharides and proteins. The in vitro activity evaluation indicated that the Maillard reaction could effectively enhance the antioxidant, antitumor and immunostimulating activities of LPPMs. The enhancement of 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and ferric reducing antioxidant power displayed both a positive correlation with the reaction time (p < 0.05). LPPMs dry-heated for three days obtained relatively strong inhibitory activity against HepG2 cells and SGC7901 cells, as well as strong immunostimulating effects on the nitric oxide production and tumor necrosis factor α secretion of macrophages. Maillard-type intermacromolecular interaction is suggested to be an effective and controllable method for improving the functional activities of polysaccharides and proteins from longan pulp.

Moisture migration, microstructure damage and protein structure changes in porcine longissimus muscle as influenced by multiple freeze-thaw cycles

This study investigated the effects of multiple freeze-thaw (F-T) cycles on water mobility, microstructure damage and protein structure changes in porcine longissimus muscle. The transverse relaxation time T2 increased significantly when muscles were subjected to multiple F-T cycles (P<0.05), which means that immobile water shifted to free water and the free water mobility increased. Multiple F-T cycles caused sarcomere shortening, Z line fractures, and I band weakening and also led to microstructural destruction of muscle tissue. The decreased free amino group content and increased dityrosine in myofibrillar protein (MP) revealed that multiple F-T cycles caused protein cross-linking and oxidation. In addition, the results of size exclusion chromatography, circular dichroism spectra, UV absorption spectra, and intrinsic fluorescence spectroscopy indirectly proved that multiple F-T cycles could cause protein aggregation and degradation, α-helix structure disruption, hydrophobic domain exposure, and conformational changes of MP. Overall, repeated F-T cycles changed the protein structure and water distribution within meat.

Bifunctional silica nanospheres with 3-aminopropyl and phenyl groups. Synthesis approach and prospects of their applications

Spherical silica particles with bifunctional (Si(CH2)3NH2/SiC6H5) surface layers were synthesized by the Stöber method using ternary alkoxysilanes systems. The influence of the synthesis conditions, such as temperature and stirring time on the process of nanoparticles formation was studied. The presence of introduced functional groups was confirmed by FTIR. The composition of the surface layers examined by elemental analysis and acid-base titration was shown to be independent from the synthesis temperature. However, the size of the obtained particles depends on the synthesis temperature and, according to photon cross-correlation spectroscopy, can be varied from 50 to 846nm. The variation of electric charges of N-functional groups was disclosed in obtained nanospheres and attributed to different surface location of these groups and their surrounding with other groups. The sorption of Cu(II) ions by functionalized silicas depends on the concentration of amino groups, which correlates with the isoelectric point values (determined to vary from 8.26 to 9.21). Bifunctional nanoparticles adsorb 99.0mg/g of methylene blue, compared with 48.0mg/g by silica sample with only amino groups. The nanospheres, both with and without adsorbed Cu2+, demonstrate reasonable antibacterial activity against S. aureus ATCC 25923, depending on particle concentration in water suspension.

Hexanediamine functionalized poly (glycidyl methacrylate-co-N-vinylpyrrolidone) particles for bilirubin removal

In this study, we provided a facile method to prepare adsorbents with high content of amino groups for bilirubin removal. Poly (glycidyl methacrylate-co-N-vinylpyrrolidone) particle adsorbents were prepared through free radical solution copolymerization followed by a phase inversion technique. Amino groups were further introduced onto the particles by grafting 1,6-hexanediamine molecules. The porosity and specific surface area of the functional particles were 92.9% and 11.8m2/g, respectively. Flourier transform infrared spectroscopy and elemental analysis confirmed the successful functionalization of polymeric particles. The cross-linker content and N-vinylpyrrolidone ratios had significant influence on the pore structure of the polymeric particles, as observed by scanning electron microscopy. Batch adsorption experiments were performed to verify bilirubin adsorption behavior of the particles, and a particle column was fabricated to further study the bilirubin removal. The particles exhibited good adsorption capacity of bilirubin without procoagulant activity, and had great potential to be used in hemoperfusion. The study opens a new route to fabricate functional polymer adsorbents.

Effect of natural cross-linkers and drying methods on physicochemical and thermal properties of dried porcine plasma protein

Abstract Porcine plasma protein (PPP) is a good source of protein from a slaughterhouse by-product; however, modification of PPP is still needed to improve its properties. The effect of various natural cross-linkers (rutin; RT, caffeic acid; CA and genipin; GP) and different drying methods (freeze drying: FD and spray drying: SD) on the properties of PPP were investigated. Cross-linking with RT, CA and GP could markedly affect the color of the modified PPP. The freeze-dried modified PPP with RT exhibited the lowest free amino group contents while using CA and GP exhibited the lowest sulfhydryl group contents. The spray-dried modified PPP with RT had lower free amino group contents than CA and GP. Modification of PPP changed the molecular weight and FT-IR spectra of both freeze-dried and spray-dried samples. The scanning electron microscope images showed that all spray-dried modified PPP samples exhibited shrinkage with a spherical shape whereas freeze-dried modified PPP exhibited a rough, grainy surface. The freeze-dried modified PPP with GP improved the thermal properties of PPP. Thus, RT, CA and GP can be considered as alternative natural cross-linkers. Moreover, the drying method reflected the properties of dried PPP for final food application.

갈색거저리 유충 단백가수분해물의 제조 및 항산화 활성

The present study was carried out to evaluate the applicability of Tenebrio molitor larvae (mealworm) as a health functional food material in order to contribute to the development of the domestic insect industry and health functional food industry. Protein hydrolysates were prepared from mealworm powder by enzymatic hydrolysis using five different proteases (alcalase, bromelain, flavourzyme, neutrase, and papain), and the hydrolysates were then tested for their antioxidant activities. Based on available amino group contents and sodium dodecyl sulphate-polyacrylamide gel electrophoresis analyses, mealworms treated with alcalase (4,781.39 μg/mL), flavourzyme (5,429.35 μg/mL), or neutrase (3,155.55 μg/mL) for 24 h showed high degree of hydrolysis (HD) value, whereas HD values of bromelain (1,800 μg/mL) and papain-treated (1,782.61 μg/mL) mealworms were much lower. Protein hydrolysates showing high HD values were further separated into > 3 kDa and ≤ 3 kDa fractions by a centrifugal filter system and then lyophilized, and the production yields of the low molecular weight protein hydrolysates (≤ 3 kDa) by alcalase, flavourzyme, and neutrase were 42.05%, 26.27%, and 30.01%, respectively. According to the RC 50 values of the protein hydrolysates (≤ 3 kDa) obtained from three different antioxidant analyses, all three hydrolysates showed similar antioxidant activities. Thus, alcalase hydrolysates showing the highest production yield of low molecular weight protein hydrolysates were further tested for their inhibitory effects on peroxidation of linoleic acid by measuring thiobarbituric acid values, and the results show that peroxidation of untreated linoleic acid increased dramatically during 6 days of incubation. However, pretreatment with the hydrolysates (100∼800 μg/mL) significantly inhibited linoleic acid peroxidation in a dose-dependent manner over 6 days.

Modification and characterisation of porcine plasma protein with natural agents as potential cross‐linkers

SummaryModification of porcine plasma protein (PPP) using the natural cross‐linkers at different concentrations of rutin (0.6–1% w/w), caffeic acid (1–3% w/w) and genipin (0.15–0.5% w/w) on chemical and thermal properties of PPP was investigated. Among these, rutin was the most significant effective natural agent corresponding to a decrease in the free amino group and sulphydryl group contents including a change in the protein bands’ intensity from SDS‐PAGE. However, genipin exhibited greater thermal properties of modified PPP. Moreover, the modification affected the colour of PPP and a change in the FT‐IR spectra of the samples. The suitable concentrations of each natural agent were 0.6% rutin, 0.5% genipin and 3% caffeic acid. Therefore, natural cross‐linkers such as rutin, caffeic acid and genipin can be considered as alternative cross‐linkers to improve the properties of PPP for food processing and biopolymer material applications as they are nontoxic.

Aminated Cellulose Nanofibers for Selective Removal of Endotoxins from Protein Solutions

Aminated cellulose nanofibers (CNFs) were prepared by attaching diaminoethane or polyethyleneimine onto microfibrillated CNFs and used for the selective removal of endotoxins (lipopolysaccharides; LPSs) from acidic protein solutions. The adsorption of the LPSs was measured at pH 7.0 and an ionic strength (μ) of 0.2. The diaminoethane-immobilized CNFs (amino group content of 0.9 meq g−1) selectively removed LPSs from protein solutions (isoelectric point (pI) 4.9–11.0) without adsorption of the proteins.

Protein adsorption of dialdehyde cellulose-crosslinked chitosan with high amino group contents

Crosslinked chitosan was prepared by Schiff base formation between the aldehyde groups of dialdehyde cellulose (DAC) and the amino groups of chitosan and a subsequent reduction. DAC was obtained through periodate oxidation of cellulose and solubilization in hot water at 100°C for 1h. Three grades of DAC-crosslinked chitosan were prepared by adding various amounts DAC. The degrees of crosslinking as determined by amino group content were 3.8, 8.3, and 12.1%, respectively. DAC-crosslinked chitosan showed higher stability in the pH 2–9 range and no cytotoxicity was identified over the course of a 21-day long-term stability test. Also, DAC-crosslinked chitosan showed remarkably high bovine serum albumin (BSA) adsorption capacity at pH 5.5 as a result of the increased amino group content, due to the reaction between DAC and chitosan molecular chains occurring at multiple points even though DAC-crosslinked chitosan showed a lower degree of crosslinking.

Development of glucose biosensors based on plasma polymerization-assisted nanocomposites of polyaniline, tin oxide, and three-dimensional reduced graphene oxide

A biosensor based on the plasma polyaniline (pPANI)-modified tin oxide and 3D reduced graphene oxide (SnO2@3D-rGO) nanocomposite was fabricated to detect glucose. The SnO2@3D-rGO nanocomposite was synthesized by simultaneously reducing 3D graphene oxide (3D-GO) and translating SnCl4 into SnO2, followed by pPANI modification. The content of amino groups in the SnO2@3D-rGO@pPANI nanocomposites depended on the plasma input powers used in plasma deposition. The SnO2@3D-rGO nanocomposite was important in the electrochemical biosensor to detect glucose. The fabricated biosensor exhibited a much higher sensitivity than that formed from individual components, namely, SnO2@3D-rGO and pPANI. This biosensor demonstrated a low detection limit of 0.047ngmL−1 (0.26nM) (S/N=3) within the concentration range of 0.1ngmL−1 to 5μgmL−1. The selectivity, stability, and practicality of the SnO2@3D-rGO@pPANI-based biosensor were observed. In conclusion, the plasma surface-modified nanocomposite is a promising candidate as biosensor for glucose detection and biological diagnosis.

Novel hexamethylene diamine-functionalized macroporous copolymer for chromium removal from aqueous solutions

Macroporous copolymers of poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [PGME] with different crosslinker (EGDMA) concentrations and porosity parameters and additionally functionalized with hexamethylene diamine [PGME-HD] were tested as a potential Cr(VI) oxyanions sorbents from aqueous solutions. Kinetics of Cr(VI) sorption was investigated in the temperature range of 298–343 K and the results were fitted to chemical-reaction and particle-diffusion models. The Cr(VI) sorption obeys the pseudo-second-order model with definite influence of pore diffusion. The temperature rise promotes chromium removal, with the maximum experimental uptake capacity of 4.21 mmol g−1 at 343 K for the sample with the highest amino group concentration. Equilibrium data were analysed with Langmuir, Freundlich and Tempkin adsorption isotherm models. Thermodynamic parameters, i.e. Gibbs free energy (ΔG0), enthalpy (ΔH0) and entropy change (ΔS0) and activation energy of sorption (Ea) were calculated. The Cr(VI) adsorption onto PGME-HD was found to be spontaneous and endothermic, with increased randomness in the system. Desorption experiments show that the chromium anions sorption was reversible and the PGME-HD sample GMA 60 HD was easily regenerated with 0.1M NaOH up to 90 % recovery in the fourth sorption/desorption cycle. In the fifth cycle, the substantial sorption loss of 37 % was observed.

Analysis of Apolipoprotein B Protein of Circulating Multiple-Modified Low-Density Lipoprotein.

Modified low-density lipoprotein (LDL) is the main source of lipid accumulation in the arterial wall affected by atherosclerosis. We aimed to compare the properties of apolipoprotein B (apoB) from native and modified LDL. Modified (desialylated) LDL and native LDL were extracted from blood of atherosclerotic patients. We characterized apoB structure of LDL particles in total LDL preparation, circulating modified LDL (cmLDL), and native LDL. Intact cmLDL had a twofold lower content of free amino groups than native LDL. Delipidated apoB from cmLDL also had a lower content of free amino groups. The rates of tryptic hydrolysis and elastase digestion of cmLDL were twofold higher in comparison to native LDL. Therefore, cmLDL from atherosclerotic patients had altered apoB properties. Our observations strengthen the hypothesis of multiple modification of LDL in the bloodstream and underscore the importance of desialylated LDL as a possible marker of atherosclerosis.

Preparation of oxidized sodium alginate with different molecular weights and its application for crosslinking collagen fiber

A series of periodate oxidized sodium alginate (OSA) were prepared as green polysaccharide-based crosslinkers. The molecular weight of OSA decreased, while their aldehyde group content increased with increasing dosage of sodium periodate. A typical OSA was further fractionated to four fractions by ethanol with a narrower molecular weight distribution. Then the crosslinking performances of OSAs/fractions on collagen fiber (CF) were investigated. DSC and SEM analyses showed that the thermal stability and dispersion degree of crosslinked CF was considerably enhanced with decreasing molecular weight of OSA. The effect of aldehyde group content of OSA on its crosslinking performance was less obvious than that of molecular weight, probably because the aldehyde group content in each OSA sample was higher than the amino group content of CF involved in the crosslinking reaction. In general, molecular weight of OSA plays a decisive role in improving properties of the crosslinked CF.

Preparation of covalently cross-linked sulfonated polybenzimidazole membranes for vanadium redox flow battery applications

A series of polybenzimidazole copolymers with varied content of pendant amino groups have been synthesized by condensation polymerization of 4,4′-dicarboxydiphenyl ether (DCDPE), 5-aminoisophthalic acid (APTA) and 3,3′-diaminobenzidine (DAB) in polyphosphoric acid at 190°C for 20h. The resulting copolymers undergo post-sulfonatation in fuming sulfuric acid at 100°C yielded the highly sulfonated polybenzimidazoles (SOPBI-NH2(x/y), ‘x/y’ refers to the monomer molar ratio of DCDPE to APTA). A series of covalently cross-linked membranes (CSOPBI-NH2(x/y)) with good mechanical properties are fabricated by solution cast technique using bisphenol A epoxy resin as a cross-linker. The CSOPBI membranes show 3–4 orders of magnitude lower VO2+ permeability and 6–30 times higher ion diffusion selectivity (proton vs. VO2+) than Nafion117. The charge-discharge behaviors of the vanadium redox flow batteries (VRBs) assembled with the CSOPBI-NH2(x/y) membranes and Nafion 117 are investigated and compared. The VRBs assembled with the CSOPBI membranes exhibit significantly higher columbic efficiency and lower self-discharge rate than that assembled with Nafion 117 owing to the extremely lower vanadium cations crossover of the former. The VRB assembled with the CSOPBI-NH2(9/1) membrane exhibits fairly high energy efficiency (~85% at 60mAcm−2) and little decay in performance is observed after 300 charge-discharge cycles.

The structural properties and antigenicity of soybean glycinin by glycation with xylose.

Soybean glycinin is considered a major allergenic protein, and glycation is widely used to reduce the allergenic potential of present allergens. Glycation of soybean glycinin with xylose at 55 °C for different lengths of time was investigated. The extent of Maillard reaction was reflected through the content changing of free amino groups, color analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Alteration in the structural properties of glycinin was characterized by Fourier transform infrared spectroscopy, and antigenicity was evaluated by indirect competitive enzyme-linked immunosorbent assay. The changes in the color of glycinin-xylose samples and the reduction of free amino group content in proteins indicated that the Maillard reaction occurred. The degree of glycation increased in glycated samples with the increase in reaction time. Glycation induced the changes in the secondary structure of glycinin and the ordered structure of proteins increased during the glycation reaction. The antigenicity of glycinin was reduced with the increase in reaction time. After glycation for 12 h, the antigenicity of glycinin declined about 18% compared with native glycinin. The application of glycation may be an efficient method to reduce the antigenicity of soybean glycinin. © 2016 Society of Chemical Industry.

Highly concentrated amino group-functionalized graphite encapsulated magnetic nanoparticles fabricated by a one-step arc discharge method

In this work, we apply a one-step direct current arc discharge method to synthesize graphite-encapsulated magnetic nanoparticles functionalized with a high concentration of amino groups uniformly without further modification or any other pre/post-treatment procedures. The synthesis was accomplished by adding different molar ratios of NH3 into He/CH4 gas mixture under various gas pressures. The optimized number of functionalized amino groups is evaluated to be ∼3.22 × 105 per nanoparticle prepared at 50 Torr with 0.1% of NH3. As the molar ratios of NH3 decrease from 1.0% to 0.1%, the optical emission peaks of CN and NH are intensified gradually, and the surface structural integrities also increase. These results indicate that NH3 not only provides -NH or -NH2 fragment species to introduce amino groups incorporating with the dangling bonds activated by H radicals, but also constructs networks to flatten the outmost graphitic surfaces of encapsulated nanoparticles. As the working gas pressure changes from 25 to 100 Torr, the outmost shells formed by the dissociated CH4/NH3 molecules tend to be relatively less disordered.

Preparation of chemically modified canola protein isolate with gum Arabic by means of Maillard reaction under wet-heating conditions

The aim of this study was to produce covalently attached conjugate between canola protein isolate (CPI) and gum Arabic (GA) in aqueous solutions via the Maillard reaction at 90°C in a model system consisting of 2% CPI and 1, 2 or 4% GA. Upon decreasing of free amino group content in the glycosylated CPI to 72%, a new band near the loading end of sodium dodecyl sulfate-polyacrylamide gel electrophoresis and a shift of CPI peak in high performance size exclusion chromatography confirmed that the covalent attachment of CPI to GA was successful. The results of secondary structure analysis suggested that grafted CPI had decreased α-helix and β-sheet levels and increased random coils level. The solubility of CPI at isoelectric point was improved remarkably after grafting with GA. The optimal conjugation conditions chosen from the further experiments were 1% of GA, 90°C and reaction time 15min.

Facile preparation of chitin nanowhisker–gold nanocluster hybrids: effect of feeding ratio and surface amino group contents on gold absorption amount

Chitin nanowhiskers (ChNWs) hybridized with the densely adsorbed gold nanoclusters (AuNCs) were facilely prepared by a simple mixing of aqueous suspensions of ChNWs and AuNCs. Adsorption of AuNCs on the ChNW surface was confirmed by transmission electron microscopy and scanning electron microscopy with energy dispersive X‐ray spectroscopy. The amounts of adsorbed AuNCs measured by thermogravimetry and combustion using a muffle furnace were in good agreement. While the amount of adsorbed AuNCs increased with AuNCs/ChNWs feeding ratio, we found only a weak dependence of adsorbed AuNC amount on the surface amino group content of ChNWs controlled by pre‐deacetylation of the starting chitin. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Synergistic and inhibitory effects of propolis and aspirin on structural changes of human hemoglobin resulting from glycation: an in vitro study

This study investigated the effects of the ethanolic extract of propolis (EEP) in the absence and presence of aspirin on the glycation-induced structural changes of human hemoglobin (Hb). Hb samples were incubated in the presence and absence of glucose (40 mM) for 5 weeks in the absence and presence of various concentrations of EEP and aspirin. Sampling was conducted at the end of each week, and the extent of glycation was evaluated by spectrophotometry, Thioflavin-T test, and by measuring free amino group contents and heme degradation products. Results showed that Hb was glycated by glucose after various incubation times reduced free amino group content, downturn absorption of and induced blue shifting in the UV–visible spectrum of Hb as well as increased amyloid structures and heme degradation. EEP prevented these changes and decreased the extent of glycation in a concentration-dependent manner. Aspirin also prevented glycation with the same efficacy as EEP (20 μg/ml). Surprisingly, the simultaneous presence of aspirin and EEP resulted in the extensive inhibition of glycation; in the 40 μg/ml concentration of EEP and aspirin, glycation was fully prevented in a synergic way. It is probable that EEP exerts its anti-glycation effect via its potent antioxidant and radical scavenging properties which decrease glycation-produced oxidative stress. In conclusion, EEP is to be introduced as an anti-glycation agent for the first time in this study. It could be developed as a natural agent for the design of new anti-glycation drugs aimed at reducing protein glycation as well as diabetic complications.

Core-shell Fe3O4@MIL-101(Fe) composites as heterogeneous catalysts of persulfate activation for the removal of Acid Orange 7.

In this study, a novel core-shell Fe3O4@MIL-101 (MIL stands for Materials of Institute Lavoisier) composite was successfully synthesized by hydrothermal method and was fully characterized by X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectra, and X-ray photoelectron spectroscopy. The composite was introduced as a catalyst to generate powerful radicals from persulfate for the removal of Acid Orange 7 in an aqueous solution. Effects of the central metal ions of MIL-101, amino group content of MIL-101, and pH were evaluated in batch experiments. It was found that both hydroxyl and sulfate radicals were generated; importantly, sulfate radicals were speculated to serve as the dominant active species in the catalytic oxidation of Acid Orange 7. In addition, a possible mechanism was proposed. This study provides new physical insights for the rational design of advanced metal-organic frameworks (MOF)-based catalysts for improved environmental remediation.