Adsorption characteristics of oligopeptides composed of acidic and basic amino acids on titanium surface

The adsorption characteristics of octapeptides, containing different numbers of aspartic acid, lysine, and alanine residues (i.e., D(4)K(0)A(4), D(4)K(1)A(3), D(4)K(3)A(1), D(4)K(4)A(0), and D(0)K(4)A(4)) on the surface of titanium (Ti) particles were investigated in the pH range of 3.0-8.8 at 30 degrees C. The adsorption isotherms for octapeptides having four plural aspartic acid residues with or without lysine residues showed two distinct adsorption modes, i.e., irreversible and reversible modes, at pHs 3.0-6.5; at pH 7.0 or higher, the adsorption mode was reversible. Increasing the number of lysine residues at a fixed number of aspartic acid residues (i.e., 4) decreased the amount of peptides adsorbed in both modes. D(4)K(4)A(0) adsorbed irreversibly at pHs 3.0-6.5, due to the fact that negatively charged carboxyl groups directly interact with a positively charged Ti surface, whereas positively charged amino groups of lysine residues are directed in an opposite direction toward the solution side, as predicted by molecular mechanics/dynamics calculations.     

Adsorption characteristics of tryptic fragments of bovine beta-lactoglobulin on a stainless steel surface

As a strategy for the analysis of the mode of protein adsorption onto stainless steel surfaces, peptides obtained by tryptic digestion of bovine beta-lactoglobulin were subjected to adsorption experiments after identification of their primary structures. In the presence of 1 mM KOH, the peptides were scarcely adsorbed onto the surfaces of stainless steel particles from the peptide mixture. The adsorption experiments on isolated peptides showed that the affinities of the peptides for stainless steel surfaces in the presence of 1 mM HNO3 were significantly different from each other. Peptides without any acidic amino acid residues were scarcely adsorbed onto the surface, whereas some peptides with acidic amino acid residues were found to be irreversibly adsorbed onto the surfaces in the acidic pH region. As for the latter peptides, the amount adsorbed on the surface increased with increasing ionic strength. These results indicated that the carboxyl groups on the side chains of the peptides play an important role in the adsorption. Furthermore, the adsorption behavior of beta-lactoglobulin itself was found to be very similar to that of one of the latter peptides.     

Uranium sorption on various forms of titanium dioxide--influence of surface area, surface charge, and impurities

Titanium dioxide (TiO(2)) has often served as a model substrate for experimental sorption studies of environmental contaminants. However, various forms of Ti-oxide have been used, and the different sorption properties of these materials have not been thoroughly studied. We investigated uranium sorption on some thoroughly characterized TiO(2) surfaces with particular attention to the influence of surface area, surface charge, and impurities. The sorption of U(VI) differed significantly between samples. Aggressive pretreatment of one material to remove impurities significantly altered the isoelectric point, determined by an electroacoustic method, but did not significantly impact U sorption. Differences in sorption properties between the various TiO(2) materials were related to the crystallographic form, morphology, surface area, and grain size, rather than to surface impurities or surface charge. In-situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopic studies showed that the spectra of the surface species of the TiO(2) samples are not significantly different, suggesting the formation of similar surface complexes. The data provide insights into the effect of different source materials and surface properties on radionuclide sorption.     

糖用活性炭吸附L-组氨酸的特性研究

研究了活性炭用量、pH、吸附平衡时间、吸附温度等因素对活性炭吸附L-组氨酸的影响。实验结果表明,活性炭吸附L-组氨酸达到吸附平衡的时间大约是80min;L-组氨酸的吸附率随着活性炭用量的增加而增大,吸附量则随着活性炭用量的增加先快速下降后又略有回升,当活性炭用量为10%(质量分数)时,吸附量达到最低点;吸附量随着溶液pH的上升呈现先上升后下降的趋势,在L-组氨酸的等电点附近,吸附量达到最大值,在pH大于12时,活性炭几乎不吸附L-组氨酸;吸附量随着温度的升高呈现先上升后下降的趋势,当温度到达70℃左右时,吸附量达到最高点。     

哈维氏弧菌磷脂酶D对不同磷脂单分子层的吸附动力学研究

基于单分子层技术研究了哈维氏弧菌来源磷脂酶D(Vh PLD)对不同磷脂单分子层的吸附动力学。探究初始表面压力条件对VhPLD吸附不同磷脂单分子层(磷脂酰胆碱(PC)、磷脂酰乙醇胺(PE)、磷脂酰丝氨酸(PS)、磷脂酰甘油(PG)和磷脂酰肌醇(PI))吸附动力学参数(k_a、k_d、K_(Ads))的影响规律。结果表明:VhPLD对磷脂单分子层的吸附动力学参数与磷脂单分子层初始表面压力密切相关;在15 m N/m条件下,VhPLD对不同磷脂单分子层吸附偏好性顺序为PC PG PS PE=PI;在20 m N/m条件下,VhPLD对不同磷脂单分子层吸附偏好性顺序为PG PI PC PS PE;在25 m N/m条件下,VhPLD对不同磷脂单分子层吸附偏好性顺序则转变为PC PS PI PE=PG。     

Adsorption mechanism of arsenic on nanocrystalline titanium dioxide

Arsenate [As(V)] and arsenite [As(III)] interactions at the solid-water interface of nanocrystalline TiO2 were investigated using electrophoretic mobility (EM) measurements, Fourier transform infrared (FTIR) spectroscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, and surface complexation modeling. The adsorption of As(V) and As(III) decreased the point of zero charge of TiO2 from 5.8 to 5.2, suggesting the formation of negatively charged inner-sphere surface complexes for both arsenic species. The EXAFS analyses indicate that both As(V) and As(III) form bidentate binuclear surface complexes as evidenced by an average Ti-As(V) bond distance of 3.30 A and Ti-As(III) bond distance of 3.35 A. The FTIR bands caused by vibrations of the adsorbed arsenic species remained at the same energy levels at different pH values. Consequently, the surface complexes on TiO2 maintained the same nonprotonated speciation at pH values from 5 to 10, and the dominant surface species were (TiO)2AsO2- and (TiO)2AsO- for As(V) and As(III), respectively. The surface configurations constrained with the spectroscopic results were formulated in the diffuse layer model to describe the adsorption behavior of As in the pH range between 4 and 12. The study suggests that TiO2 is an effective adsorbent for As removal due to its high surface area and the presence of high affinity surface hydroxyl groups.     

辣木籽壳对亚甲基蓝的吸附特性

以辣木籽壳作为吸附剂,考察了吸附时间、颗粒大小、温度、溶液初始浓度和pH对其吸附亚甲基蓝的影响;采用吸附等温模型和动力学模型对数据进行拟合;通过扫描电镜和红外光谱进行表征。结果表明:在辣木籽壳加入量为10g/L时,最佳吸附条件为吸附时间1.5h,颗粒大小80目,温度25℃,亚甲基蓝溶液浓度200mg/L,pH5;吸附过程符合Langmuir模型和准二级动力学模型,最大理论饱和吸附量为94.25mg/g;吸附过程为物理吸附和化学吸附共同作用的结果,以物理吸附为主。     

Immunochemical examination of the surface physico-chemical properties of various dicotyledonous and monocotyledonous globulin seed storage proteins

Immunochemical analysis of the surface properties of seed globulins indicated that the 11S seed globulins of monocotyledonous and dicotyledonous plants possibly share some similarity in their primary structures, i.e. amino acid sequence on their surface topography as well in their structural conformation. Although homologies were found in all globulins, stronger antigenic responses were found to occur between the amaranth globulin antibody and the purified globulins from monocotyledonous than those originating from dicotyledonous seeds. Homologies in primary structure were found to occur almost exclusively in the ‘basic’ (20–27 000 Da) type subunit of the respective globulins. Data would imply that gene families encoding for these different proteins were derived from a common ancestral gene and must have been present before divergence of the angiosperms into dicotyledonous and monocotyledonous plants.     

Ability of various proteins to form thermostable gels with propylene glycol alginate

Propylene glycol alginate forms gels with proteins in alkaline conditions (pH 9.3 to 10.5). The ability of gelatin, casein, soya isolate, whey protein concentrate, egg albumin and bovine serum albumin to form ‘protein-alginate’ gels was investigated. Conditions were varied so as to alter the structures of the protein and observe the effect on gel formation. These conditions include changing pH, heat, the action of nitrous acid, SDS, mercaptoethanol, hydrogen bond breakers and changing concentration of the protein. The extent of gel formation was indicated by its rigidity modulus. The tertiary structure of the protein appears to be a very important factor in the gel formation. The gels are readily brought down to pH values more suitable for foods, and are stable to heating at 95°C and to freeze-thawing.     

Degradation characteristics of proteins in cheonggukjang (fermented unsalted soybean paste) prepared with various soybean cultivars

In order to select the most ideal soybean cultivars for producing cheonggukjang, the protein degradation characteristics of cheonggukjangs prepared with 30 different soybean cultivars were compared. Cheonggukjang prepared with ‘Nampung’ (18.00±0.28%) and ‘Sohwang’ (17.91±0.63%) soybeans showed the highest contents of viscous substances. Acidic-protease activity was highest (590.24±2.92 μg/mL) in cheonggukjang prepared with small ‘Pungsannalmul’ soybeans. Neutral-protease activity was highest (528.13±3.11 and 527.36±0.44 μg/mL, respectively) in cheonggukjang prepared with ‘Singi’ and ‘Nampung’ soybeans. Cheonggukjang prepared with ‘Wonkwang’ and ‘Sohwang’ soybeans had amino-type nitrogen contents of 780.50±2.92 and 729.95±1.07 mg%, respectively. Glutamic acid, which is a major component of viscous substances, was also detected. Although total free amino acid levels in cheonggukjang prepared with ‘Daewon’ and ‘Wonkwang’ soybeans measured 2,551.21 and 2,340.02 mg%, respectively, cheonggukjang prepared with black soybeans exhibited low levels of total free amino acids. Therefore, based on protein degradation characteristics, large ‘Daewon’ soybeans and small ‘Wonkwang’ soybeans were the most suitable for producing cheonggukjang.     

Adsorption kinetics and thermodynamic parameters of egg white proteins

This study evaluated the adsorption process in agitated tanks with the proteins ovalbumin, conalbumin, and lysozyme by employing anion and cation exchange resins at different temperatures (5, 15, 25, and 35 °C). The equilibrium data showed that the different temperatures and adsorbents (cationic and anionic) preferentially influenced adsorption of the studied proteins. The employed isotherm model (Langmuir) adjusted well to the equilibrium data of these proteins. For the adsorption kinetics, two models were employed: pore diffusivity and a second-order kinetic model, in which the second presented the best fit to the experimental data. The calculated thermodynamic parameters indicated a spontaneous, viable, and endothermic process and also showed that entropy has a greater effect on the process than enthalpy.     

沙棘籽生物炭对苯酚的吸附特性研究

为促进沙棘籽的资源化利用,以沙棘籽为原材料,采用慢速热解技术分别于300、400、500℃条件下制备生物炭吸附剂(BC300、BC400、BC500),研究其去除水中苯酚的效果。吸附实验结果表明,生物炭的制备温度明显影响其对苯酚的吸附效果,3种温度制备的生物炭对苯酚的吸附能力表现为BC500BC400BC300。苯酚的初始浓度、吸附温度、时间等因素均影响吸附效果。45℃下苯酚初始浓度为20mg/L时,BC500对苯酚的去除率最高,达92.1%,生物炭对苯酚的等温吸附线符合Langmuir模式和Freundlich模式。探明了沙棘籽制备生物炭吸附剂及其去除苯酚的最适条件,可为沙棘籽应用于苯酚等有机污染物的去除提供理论依据。     

Adsorption dynamics and surface activity at equilibrium of whey proteins and hydroxypropyl–methyl–cellulose mixtures at the air-water interface

In this work the competitive behaviour of whey protein concentrate (WPC) and three well-characterized hydroxypropyl–methyl–celluloses (HPMCs), so-called E4M, E50LV and F4M, with different interfacial properties, were studied by measurement of the dynamics of adsorption and surface pressure isotherms. Such differences may be attributed to differences in the molecular weight and degree and molar substitution among the HPMCs. Thus, E4M having the highest molecular weight showed the highest surface activity among the HPMCs. The lower surface activity of F4M, in comparison to E50LV, may be attributed to its lower degree of total substitution. The experiments were performed at constant temperature (20 °C), pH 7, ionic strength 0.05 M and variable concentrations of the components.The differences observed between mixed systems were according to the relative bulk concentration of biopolymers and molecular structure of HPMC. In the presence of E4M a strong competence for the interface can be observed at short adsorption time. As E4M is more surface active than WPC, the replacement of E4M at the interface by WPC resulted in lower surface pressure. The mixture approached E4M behaviour at longer adsorption time. An additive or synergistic behaviour was observed for celluloses with lower surface activity (E50LV and F4M) at the lowest WPC and HPMC concentrations in the aqueous phase. A depletion mechanism in the vicinity of the interface would predominate in the presence of E50LV and F4M over the competence for the interface, giving rise to a cooperative behaviour. When WPC saturated the interface and the HPMC concentration in the aqueous phase was low enough, WPC dominated the surface pressure at long-term adsorption.     

我国不同品种黄牛肉质研究概述

我国黄牛品种较多,了解其牛肉本质特性对于优质黄牛资源的开发利用具有重要意义。该文就我国不同品种肉用黄牛及其杂交牛的肉品品质进行了总结,包括其肉色和嫩度等食用品质及蛋白质、脂肪、氨基酸、脂肪酸、矿物质与维生素等营养品质。我国黄牛(尤其是杂交肉牛品种)食用品质较好,具有高蛋白低脂肪、富含矿物质、氨基酸评价优良等特征,但是不同品种之间的脂肪酸的含量及组分等信息匮乏,亟需开展大量的系统性研究工作填补这一空白。     

Fat spectro-colorimetric characteristics of lambs switched from a low to a high dietary carotenoid level for various durations before slaughter

This study investigated the changes in fat reflectance spectrum characteristics and color in lambs switched from a low to a high dietary carotenoid level for various durations before slaughter. Six treatments, feeding a high dietary carotenoid level for 0, 15, 30, 45, 60 or 75days before slaughter, were compared in individually indoor penned lambs. Each treatment used 10 Romane lambs; feeding management ensured similar growth pattern and carcass weight for all the treatment groups. There was a change in reflectance spectrum characteristics and yellowness of subcutaneous fat as early as 15days after the switch. Mean concentration of carotenoid pigments and yellowness of subcutaneous fat increased linearly with the duration of the high dietary carotenoid level. In perirenal fat, the change in reflectance spectrum characteristics was observed as early as 15days after the switch, but the response to the duration of the high dietary carotenoid level was curvilinear.     

Fat spectro-colorimetric characteristics of lambs switched from a low to a high dietary carotenoid level for various durations before slaughter

This study investigated the changes in fat reflectance spectrum characteristics and color in lambs switched from a low to a high dietary carotenoid level for various durations before slaughter. Six treatments, feeding a high dietary carotenoid level for 0, 15, 30, 45, 60 or 75 days before slaughter, were compared in individually indoor penned lambs. Each treatment used 10 Romane lambs; feeding management ensured similar growth pattern and carcass weight for all the treatment groups. There was a change in reflectance spectrum characteristics and yellowness of subcutaneous fat as early as 15 days after the switch. Mean concentration of carotenoid pigments and yellowness of subcutaneous fat increased linearly with the duration of the high dietary carotenoid level. In perirenal fat, the change in reflectance spectrum characteristics was observed as early as 15 days after the switch, but the response to the duration of the high dietary carotenoid level was curvilinear.     

二氧化钛/石墨氮化碳复合材料对棒曲霉素的吸附与光催化降解作用研究

摘 要：目的 探究TiO2/g-C3N4复合材料对棒曲霉素(patulin, PAT)的吸附与光催化降解作用研究。方法 通过超声混合后再煅烧的方法制备二氧化钛(Titanium dioxide, TiO2)和石墨氮化碳(Graphite carbon nitride, g-C3N4)的复合材料(TiO2/g-C3N4)。分别使用傅里叶转换红外光谱分析仪(Fourier Transform Infrared Spectrometer, FTIR)和比表面及孔径分析仪(BET)对3种材料进行测试分析,并研究单一材料与复合材料分别对PAT的吸附作用、复合材料在可见光下的光催化效果及及暗吸附与光降解之间的协同作用。结果 TiO2/g-C3N4复合材料的FTIR图中出现了TiO2的特征峰O-H基团和Ti-O、g-C3N4的特征峰C=N和CN,表明成功合成了TiO2/g-C3N4复合材料。结果表明TiO2和g-C3N4复合后的吸附及光催化降解效果明显优于单一材料,且TiO2/g-C3N4复合材料暗吸附与光降解之间存在协同作用,在温度为30℃、复合材料添加量为10 mg、吸附时间3 min、光照时间5 min时,可完全降解初始质量浓度为0.5 μg/mL的PAT。此外,TiO2/g-C3N4对PAT的吸附存在多分子层化学吸附,且过程符合准二级动力学模型,对PAT的光催化降解过程符合准一级动力学模型。结论 该复合材料可快速、高效地去除PAT,因此在果蔬及其制品、谷物和饲料中PAT的去除方面有较好的应用前景。     

Ultrasound and effect on the surface hydrophobicity of proteins: a meta-analysis

This review aims to investigate and evaluate the effect of ultrasound process parameters on the interfacial properties (surface hydrophobicity) of food proteins. The data obtained from English published papers accessed on Web of Science, PubMed and Wiley published from 2013 to 2021 allowed a table overview construction and a meta-analysis. Study selection was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses method. A total of 40 relevant reports and 185 data used for meta-analysis were considered. In general, the results revealed that the use of the ultrasound process increased the surface hydrophobicity of proteins. Processing time, power, amplitude and ultrasound frequency were significant in protein modification. The findings showed that the ultrasound process parameters should be considered to assess the effect on the modification and improvement of the interfacial properties of proteins.     

新生磷酸钙对没食子酸的吸附性能研究

研究了新生磷酸钙对没食子酸的吸附特性。根据对吸附动力学数据进行的粒内扩散模型、准一级动力学模型和准二级动力学模型的拟合结果可知,当没食子酸的初始浓度分别为25、50、75mg/L时,新生磷酸钙对没食子酸的吸附过程均可用准二级动力学方程描述(R2=0.9943~0.9946)。pH是影响吸附作用的重要因素,当pH在7.2~7.5之间时,没食子酸的吸附量达到最大值。吸附等温曲线符合Langmuir模型(R2=0.9965),由Langmuir线性拟合方程可得新生磷酸钙对没食子酸的饱和吸附量为8.4317mg/g。