一种新型抗氧化五肽的纯化、鉴定与表征

以黑鲨鱼皮为原料,利用蛋白酶酶解制备和分离纯化抗氧化多肽,并探究其抗氧化机理。以1,1-二苯基-2-苦肼基（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基清除率为主要指标,以水解度为辅助指标,优化酶解工艺条件。通过反相高效液相色谱和电喷雾四极杆飞行时间质谱分离纯化和鉴定氨基酸序列并探究其体外抗氧化活性。结果显示,最佳水解蛋白酶为碱性蛋白酶,最优酶解工艺为pH 8.0、酶添加量311 U/mL、底物质量分数3%、酶解温度45 ℃、酶解时间4.9 h,所得的酶解液DPPH自由基清除率为77.61%,水解度为14.21%。经反相高效液相色谱分离,得到组分F19的DPPH自由基清除能力最强。经鉴定,选择抗氧化活性高的总离子流色谱峰（保留时间为10.02 min左右）进行一级质谱和二级质谱分析,获得纯化的新型抗氧化五肽,其分子质量为461 Da,氨基酸序列结构为Pro-Gly-Gly-Thr-Met,其DPPH自由基清除率为75.01%（1.0 mg/mL）,氧自由基吸收能力（以Trolox当量计）为2490.01 μmol/g。新型五肽的Pro和Met在抗氧化中起到关键性作用。本研究为黑鲨鱼皮抗氧化五肽的抗氧化机理及其构效关系提供了一定理论依据。     

Modeling of biodiesel production: Performance comparison of Box-Behnken,face central composite and full factorial design

The performances of the response surface methodology (RSM) in connection with the Box-Behnken, face central composite or full factorial design (BBD, FCCD or FFD, respectively) were compared for the use in modeling of the NaOH-catalyzed sunflower oil ethanolysis. The influence of temperature, catalyst loading, and ethanol-to-oil molar ratio (EOMR) on fatty acid ethyl esters (FAEE) content was evaluated. All three multivariate strategies were efficient in the statistical modeling and optimization of the influential process variables but BBD and FCCD realization involved less number of experiments, generating smaller costs, requiring less work and consuming shorter time than the corresponding FFD. All three designs resulted in the same optimal catalyst loading (1.25% of oil) and EOMR (12:1). The reduced two-factorinteraction (2FI) models based on the BBD and FCCD defined a range of optimal reaction temperature (25℃-75℃) and 25℃, respectively while the same model based on the 3³ FFD appointed 75℃. The predicted FAEE content of about 97%-98.0% was close to the experimentally obtained FAEE content of about 97.0%-97.6% under the optimal reaction conditions. Therefore, the simpler BBD or FCCD might successfully be applied for statistical modeling of biodiesel production processes instead of the more extensive, more laborious and more expensive FFD.     

Effect of hydrolyzed collagen on thermal,mechanical and biological properties of poly(lactic acid) bionanocomposites

Iranian Polymer Journal - Bionanocomposites based on poly(lactic acid) (PLA), plasticized with commercial tributyl o-acetyl citrate (ATBC) and containing hydrolyzed collagen (HC) up to...     

DMSO as solvent on the synthesis of flame-retardant polyether polyols

Polyether polyols with flame-retardant properties are synthesized using glycerol phosphate disodium salt as an initiator and dimethyl sulfoxide (DMSO) as a solvent. The molecular weight of the polyol decreased when higher solvent to initiator ratios were used, revealing that a larger amount of salt was activated. In addition, the larger the amount of activated salt was, the higher the percentage of phosphorous was in the final polyol. Glycerol phosphate disodium salt was still partially insoluble in the studied proportions of DMSO. Thus, the recovery and reuse of this part of the salt for the synthesis of new flame-retardant polyols were evaluated. The recovered salt promoted a shorter induction period because it presented a larger amount of deprotonated hydroxyl groups. In addition, there were no differences between both synthesized polyols, indicating that it is possible to use the recovered salt in the same way as it is used commercially with the advantage of a shorter induction period for polymerization. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47042.     

Hydrogel wound dressings based on chitosan and xyloglucan: Development and characterization

Xyloglucan is a polysaccharide isolated from chia seed gum (Salvia hispanica L.) and can act as a soluble fiber. In this investigation, several porous hydrogels were prepared from mixtures of chitosan and xyloglucan. To characterize these biomaterials, their mechanical, hydrophilic, structural, and morphological properties were measured, as well as their biodegradability and antimicrobial activity. The pore sizes of the porous hydrogels were 32.8–101.6 μm, and their water retention capacity is proportional to the added amount of xyloglucan. Dynamic degradation of the porous hydrogels with lysozymes showed progressive weight loss during the 14 days of testing. The mechanical properties improved slightly after the addition of xyloglucan. All of these results indicate that the incorporation of vegetable-derived polymers such as xyloglucan improves the properties of chitosan without affecting its antimicrobial capacity. Thus, biomaterials based on chitosan and xyloglucan are a promising option for the design of hydrogel wound dressings for medical applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47342.     

The Effect of the Ionizing Radiation on Hydroxyapatite–Polydimethylsiloxane Layers

The bio hydroxyapatite (HAp) was used from a long time in different medical and environmental applications. The HAp layers with a uniform surface were used for various medical applications such as orthopedic and dental metal implants. In this work, we reported on the influence of X‐ray radiation on the structural and morphological properties of composite layers based on HAp and polydimethylsiloxane (PDMS) deposited on titanium substrates. The HAp:PDMS layers were investigated by different complementary methods such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and glow discharge optical emission spectrometry (GDOES). FTIR spectral analysis showed that the molecular structure of the coatings was not changed after their irradiation even though, the depth profile analysis performed by GDOES indicated a depletion of Ca and P elements from the HAp:PDMS irradiated samples. By SEM, we showed that the morphological features of the coatings were also changed, as the irradiated layers are delaminated. The biological assays confirmed that the antibacterial activity of HAp:PDMS composite layers increased after irradiation. The results obtained in this study highlighted that the biological properties of HAp:PDMS layers could be influenced by irradiation. POLYM. ENG. SCI., 59:2406–2412, 2019. © 2019 Society of Plastics Engineers     

Colloidal synthesis of Au nanoparticles using polyelectrolytes with 1,3,4-thiadiazole as reducing agents

Heterocyclic compounds are well known for their biological activity and coordination properties. Some heterocyclic compounds have been employed in the stabilization against coalescence of metallic nanoparticles in colloidal solutions, for example, tetrazole, triazole, and pyrazole. The aim of this work is to design new polyelectrolytes with heterocyclic pendant groups useful as reducing agents of Au³⁺ and as stabilizing agents for the synthesis of colloidal Au nanoparticles. Thus, polyelectrolytes with thiosemicarbazone and 1,3,4-thiadiazole pendant groups were used as reducing agents of Au³⁺ ions and stabilizing agents of Au nanoparticles. The voltammetry study of the polyelectrolytes showed that one with thiosemicarbazone pendant groups is the better reducing agent than polyelectrolytes with heterocyclic pendant groups. The polyelectrolytes can control the growth of the nanoparticles, obtaining structures with an average size of 9 nm. In this study, it was concluded that the nature of the heterocyclic group does not have an effect on the shape of nanoparticles and quasi-spherical nanoparticles were obtained with all polyelectrolytes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47790.     

Unmasking Sensory Defects of Olive Oils Flavored with Basil and Oregano Using an Electronic Tongue-Chemometric Tool

Olive oil price and consumers’ preference depend on the commercial grade classification that can decrease if any sensory defect is perceived leading to an economic loss. Enriched oils, obtained by incorporating dried aromatic herbs, spices, or essential oils, which is a common practice in the Mediterranean region, are commercially available. This practice may conceal the fraudulent purpose of masking the perception of sensory defects. The detection of this type of fraud is a difficult task, requiring sensory analysis. Thus, in this study, extra-virgin and lampante olive oils, the latter classification being due to the perception of an intense winey-vinegary defect, were deliberately enriched with different amounts of basil-dried herbs and oregano-dried herbs. Sensory analysis showed that, depending on the aromatic herb and on the added amount (0.011–0.110 g herb per kg oil), the defect intensity could be masked leading to an erroneous classification of flavored lampante oils as flavored virgin oils. In contrast, the electronic tongue-chemometric approach could unmask the defect in flavored oils (predictive sensitivities: 70–78%) and semiquantitatively discriminate flavored oils according to the added levels of basil or oregano (predictive sensitivities: 93–100%). The electronic tongue approach showed satisfactory unmasking performance when compared with the sensory panel, and so, its future application as a quality control taste-sensor device for disclosing olive oil sensory defects masked by the incorporation of flavoring agents may be forseen.