Simultaneous determination of calcium,magnesium and zinc in different foodstuffs and pharmaceutical samples with continuous wavelet transforms

This work presents novel and very simple spectrophotometric methods by ratio spectra–continuous wavelet transformation for the simultaneous determination of ternary mixtures of calcium, magnesium and zinc without prior separation steps. The methods are based on the complexation reaction of these elements with bromopyrogallo red (BPR) at pH 9.4. The results showed that calcium, magnesium and zinc could be determined simultaneously in the range of 0.1–3.5 mg L⁻¹, 0.2–3.2 mg L⁻¹ and 0.5–3.8 mg L⁻¹, respectively. Mexican hat and Morlet from the family of continuous wavelet transforms were selected and applied under the optimal conditions for multi-component determinations. In this study for improving the sensitivity the normalized spectra of divisors were used instead of standard spectrum of divisor. The method was tested by analyzing various synthetic ternary mixtures of Ca²⁺, Mg²⁺ and Zn²⁺. Under the working conditions, the proposed methods were successfully applied to simultaneous determination of elements in cows’ milk, powder milk, pharmaceutical product and tea samples.     

Dephosphorylation of myosin regulatory light chain modulates actin–myosin interaction adverse to meat tenderness

The objective of this study was to investigate the relationship between the dephosphorylation of myosin regulatory light chain and actin–myosin interaction after muscle homogenate was treated with alkaline phosphatase and phosphatase inhibitor. The myosin regulatory light chain was significantly dephosphorylated by alkaline phosphatase after incubation. Among different groups, dephosphorylated myosin regulatory light chain to a much greater extent leads to a lower actomyosin dissociation degree, thereby raising the actomyosin ATPase activity, whereas it exhibits a higher actomyosin dissociation degree and a lower actomyosin ATPase activity when the myosin regulatory light chain was in a low dephosphorylated state. The data suggest that the dephosphorylation of myosin regulatory light chain modulates actomyosin dissociation (the number of myosin interact with actin) negatively and has a positive influence on actomyosin ATPase activity (the interacting force between myosin and actin).     

Physicochemical characterization of muscle proteins from different regions of mackerel (Rastrelliger kanagurta)

Physicochemical characteristics of proteins extracted from muscles excised from four distinct regions of mackerel were examined. Three regions were identified based on their fin position; namely anterior muscle, median muscle, posterior muscle and red muscles from beneath the lateral line. The biochemical characteristics like reactive sulphydryl groups, surface hydrophobicity, Ca²⁺ ATPase activity, turbidity, proximate composition and the functional characteristics such as viscosity, emulsion activity index (EAI) and emulsion stability (ES) were studied in the samples, from different regions. Sarcoplasmic protein (SPP) solubility was found to be higher in red muscles compared to that of white muscles, whereas myofibrillar protein (MFP) solubility was higher in white muscles particularly in the posterior portion. The MFP from posterior white muscles showed better viscosity, surface hydrophobicity and Ca²⁺ ATPase activity, which in turn contributed to the higher EAI and ES of this muscle portion. Variations in composition, electrophoretic pattern of proteins and selected functional properties (EAI) were noticed between red and white muscles, which may be of significance from the utilization point of the fish.     

Accurate determination of the Ca activity in milk-based systems by Ca-ISE: Effects of ionic composition on the single Ca activity coefficient and liquid junction potentials

Calcium ion selective electrode (Ca-ISE) was found to underestimate the actual Ca²⁺ ion activity in simulated milk ultrafiltrate (SMUF) and milk. It is shown that the ionic compositional difference between conventional calibration solutions and milk type samples had a significant effect on the single Ca²⁺ activity coefficient, which generates the erroneous estimate of Ca²⁺ activities in SMUF and milk. This study tests new standards with ionic profiles similar to SMUF, aiming at the reduction of the errors generated by the compositional difference between conventional standards and milk samples. As a result, the new standards showed a significant improvement in the accuracy of Ca²⁺ activity and Ca²⁺ activity coefficient over the conventional standards. The systematic error is reduced from 20% to 5% for SMUF and from 44% to 15% for milk. In addition, the new standards generate liquid junction potentials that are practically insignificant.     

C NMR and electrospray ionization mass spectrometric study of sucrose aqueous solutions at high pH: NMR measurement of sucrose dissociation constant

The ¹³C NMR technique is used for the measurement of the first dissociation constant of sucrose (HL) in highly alkaline solutions. In 1.0 M NaCl/NaOH medium and for 25 °C, the concentration dissociation constant (pK₁) was 13.1 ± 0.3; and, for 60 °C, pK₁ = 12.30 ± 0.05. The β-d-fructofuranosyl ring was found to be responsible for dissociation. The NMR data reveal no clear evidence of the second dissociation step below pH 14, either at 25 °C or at 60 °C. In the solutions with 4–10 mol dm⁻³ NaOH content the ¹³C NMR technique indicated the chemical shift changes, treated as the second dissociation step of sucrose and a sodium complex formation. A very rough estimation, for variable ionic strength, gives the value: pK₂ ∼ 15.8 ± 0.8. The anionic species L⁻ and NaH₋₁L⁻ have been registered by electrospray ionization time-of-flight mass spectrometry (ESI-ToF MS) for 0.01 M sucrose solutions with initial pH 13.     

The effects of MgSO4, d-glucono-δ-lactone (GDL), sucrose,and urea on gelation properties of pectic polysaccharide from soy hull

The monosaccharide composition of pectic polysaccharide extracted from soy hull under assistance of microwave was firstly analyzed. Soy hull pectic polysaccharide (SHPP) mainly contains galactose, xylose, galacturonic acid, arabinose, glucose and rhamnose with a molar ratio of 4.7:2.5:1.5:3.8:3.2:3.0. The gelation properties of SHPP as a function of Mg²⁺, GDL, sucrose, and urea concentration were then systematically studied. Mg²⁺ can induce the gelation of SHPP but low concentration Mg²⁺ require more time to cross-linking SHPP molecular chains. GDL can strengthen the elasticity of SHPP/Mg²⁺ gel, while sucrose can also strengthen the network through hydrophobic interaction, however 30 wt% sucrose can weaken the SHPP/Mg²⁺ gel network. 2 mol/L urea can collapse the gel network formed by 3 wt% GDL with 0.1 mol/L Mg²⁺, which suggests that the junction zone of SHPP/GDL/Mg²⁺ system is formed through hydrogen bonding.     

造纸污泥基纳米复合材料的制备及其对废水中重金属的吸附

利用造纸污泥与壳聚糖制备造纸污泥-壳聚糖(SL-CSA)纳米复合吸附材料,研究了SL-CSA纳米复合材料对废水中铬离子(Cd²⁺)和铅离子(Pb2+)的吸附性能。通过傅里叶变换红外光谱仪(FT-IR)和扫描电子显微镜(SEM)表征证明了复合材料的成功制备。吸附实验表明,SL-CSA纳米复合材料对Cd²⁺和Pb²⁺的吸附均遵循准二级动力学方程,属于化学吸附。根据Langmuir模型,SL-CSA纳米复合材料对Cd²⁺和Pb2+的最大吸附量分别为314.05 mg/g和320.06 mg/g。     

Relationship between histochemical, structural characteristics and oxidative stability of rhea limb muscles

Histochemical and structural characteristics were investigated in Gastrocnemius pars interna (GN) and Iliofiburalis (IF) limb muscles of Rhea americana. The average myofibre area cross-section was greater in GN than IF muscle (p < 0.001), whereas the fibre density per section was higher in IF than GN muscle. The only type of myofibre found in both the rhea limb muscles analysed in this study was fast-twitch oxidative-glycolytic fibres (FOG). Immunolabelling analysis and ultrastructural observation of myofibres confirmed the contractile and metabolic characteristics of rhea myofibres, revealing the absolute fast isoform of myosin heavy chain and the abundance of glycogen and mitochondria inside the cells, mainly in IF muscle. These findings converged with previous results on the biochemical and physicochemical characteristics of rhea meat to provide further evidence that myofibre composition substantially influences the oxidative reactions of the muscle and therefore the meat quality, but more in-depth examination is needed to establish the links between myofibre characteristics, myofibre glycogen concentration and meat stability during storage.     

Temperature induced denaturation of myosin: Evidence of structural alterations of myosin subfragment-1

Denaturation of myofibrillar proteins in porcine longissimus thoracis et lumborum muscle was investigated after pre-rigor temperature incubation at 20, 30 and 40 °C. At 24 h myofibrils were isolated and myosin was further cleaved by chymotrypsin. High temperature pre-rigor induced release of myosin S1 (subfragment-1), less (P < 0.05) Ca²⁺-ATPase activity and structural alterations of the region of the myosin molecule that harbors S1. Surface hydrophobicity of myofibrils from the 40 °C group increased (P < 0.001), suggesting a temperature-induced structural rearrangement exposing hydrophobic groups on the surface of myofibrils which in turn may explain the reduced water-holding of PSE meat.     

Influence of Ni and Co on methanogenic activity and the amounts of coenzymes involved in methanogenesis

The requirement of Ni²⁺ and Co²⁺ addition on methanogenic activity and the coenzymes involved in methanogenesis were investigated in anaerobic continuous cultivation with synthetic wastewater using acetate as the sole carbon source. Addition of Ni²⁺ and Co²⁺ to the synthetic wastewater drastically increased the maximum dilution rate of the cultivation. The concentrations of coenzymes F₄₃₀ and corrinoids in the biomass increased to 0.62 μmol-Ni/g-VSS and 0.67 μmol-Co/g-VSS, respectively with the increase of the dilution rate. Methanogenic activity of the culture broth also increased with an increase of dilution rate. However, without addition of Ni²⁺ and Co²⁺, F₄₃₀ and corrinoids were not detected in the biomass and methanogenic activity was only a trace level at a dilution rate of 0.025 d⁻¹. When the amounts of Ni²⁺ and Co²⁺ added at a dilution rate of 0.6 d⁻¹ were lowered in steps, the concentrations of F₄₃₀ and corrinoids in the biomass and methanogenic activity decreased with decreasing amounts of Ni²⁺ and Co²⁺ added. These results suggest that Ni²⁺ and Co²⁺ were required for the methane-producing reactions via increases of coenzymes F₄₃₀ and corrinoids.     

两株乳酸菌对铅的吸附作用

以双歧杆菌和鼠李糖乳杆菌为研究对象,研究其对不同浓度铅的耐受性和吸附性,对pH值、初始湿菌量以及初始铅离子浓度进行单因素试验,利用热力学及动力学模型对两株乳酸菌结合铅离子的过程进行模拟。分析结果表明:两株菌对铅的耐受性较好,初始铅离子浓度为50 mg/L,吸附最佳条件是pH值6,初始湿菌添加量1g/L,该条件下双歧杆菌和鼠李糖乳杆菌对铅的吸附率分别为97.44%,96.87%;Langmuir-Freundlich模型比Langmuir模型和Freundlich模型更适合其结合铅离子的过程,准二级动力学模型比准一级动力学模型更适合,说明两株菌与铅的作用机制为化学吸附和物理吸附。     

Effect of reaction pH on the photodegradation of model melanoidins

The effect was studied of the pH of the amino-carbonyl reaction on the photodegradation of model melanoidins. Nondialyzable model melanoidins were prepared from glucose and lysine with or without initial pH control to 7.0.: 2 mol/l phosphate buffer (buffer-melanoidin) and pH adjustment at the reaction start with NaHCO₃ (NaHCO₃-melanoidin). Melanoidin was also prepared from glucose and the lysine-Cu²⁺complex to investigate the difference of complexes between melanoidin and Cu²⁺ (Cu²⁺-melanoidin). Each melanoidin solution was irradiated with a Xe or tungsten-halogen lamp under dissolved oxygen or by the continuous supply of oxygen in a Cu²⁺/O₂ or ascorbic acid/Cu²⁺/O₂ system. The effects of the concentrations of Cu²⁺ and melanoidin, reaction pH value, and metal ion species on the decolorization rate in the Cu²⁺/O₂ system were investigated. The most effective factor for decolorization was found to be the melanoidin concentration. The decolorization rate was negligible when 14 g/l of Cu²⁺-melanoidin was photodegraded in the ascorbic acid/Cu²⁺/O₂ system under dissolved oxygen, although depolymerization was observed. Photodegradation of NaHCO₃-melanoidins in the Cu²⁺/O₂ system by the continuous supply of oxygen resulted in an increased decolorization rate, decreased molecular mass, production of low-molecular-weight compounds, release of free lysine, and pI change. The buffer- and Cu²⁺-melanoidins did not show changes in chemical characteristics similar to those of the NaHCO₃-melanoidin.     

Oxidation of corn oil at room temperature: Primary and secondary oxidation products and determination of their concentration in the oil liquid matrix from H nuclear magnetic resonance data

The oil liquid matrix of several corn oil samples that have been stored at room temperature in closed receptacles for different periods of time is studied by means of ¹H nuclear magnetic resonance (¹H NMR), in order to further knowledge about this type of edible oil oxidation. As expected, the degradation of linoleic acyl groups predominates. In samples at early oxidation stages the presence of hydroperoxides and of (Z,E) conjugated-dienic systems is demonstrated, the concentration of the first group being higher than that of the second. In addition to these compounds, the presence of hydroxy derivatives supporting (Z,E) conjugated-dienic systems, as well as of hydroperoxy derivatives supporting (E,E) conjugated-dienic systems, in samples at intermediate and advanced oxidation stages, is also shown. Corn oil samples at advanced stages of oxidation also contain aldehydes, among which there are alkanals, (E)-2-alkenals, (E,E)-2,4-alkadienals, 4-hydroxy-(E)-2-alkenals, 4-hydroperoxy-(E)-2-alkenals and 4,5-epoxy-(E)-2-alkenals. The concentrations of the different kinds of intermediate compounds above mentioned as well as of the different kinds of aldehydes present in the oil liquid matrix were determined. These latter compounds can be either free or joined to truncated structures of triglycerides. In addition, a principal component analysis between storage conditions and oxidation level of the samples was carried out.     

Study on the structural and luminous properties of two kinds self-luminous fibers

Abstract

Reports on the structural and optical characteristics of rare earth luminous fibers have been launched, two kinds of red light emitting luminous fibers: SrAl₂O₄:Eu²⁺,Dy³⁺/light conversion agent-PET as well as SrAl₂O₄:Eu²⁺,Dy³⁺-light conversion agent-PET were artificially manufactured, using rare-earth strontium aluminate SrAl₂O₄:Eu²⁺, Dy³⁺ as the rare-earth luminescent material. Their luminous properties depended on Eu²⁺, Dy³⁺ and fiber-forming polymers, with dispersion agent as a matrix. Herein, studies related to emitting red light of this two kinds of luminous fibers have been widely carried out. The morphology and EDS as well as luminous properties of the resulting samples were characterized. The results showed that the emission spectrum had a broad band from 450 to 590?nm with the two highest excitation intensity located at 520 and 580?nm for SrAl₂O₄:Eu²⁺, Dy³⁺-light conversion agent-PET, and at 520 and 605?nm for SrAl₂O₄:Eu²⁺, Dy³⁺/light conversion agent-PET. The brightness and the afterglow time of SrAl₂O₄:Eu²⁺, Dy³⁺-light conversion agent-PET were lower than that of SrAl₂O₄:Eu²⁺, Dy³⁺/light conversion agent-PET.     

Rheological properties of sodium alginate in an aqueous system during gelation in relation to supermolecular structures and Ca binding

Gelation behavior of sodium alginate was investigated in an aqueous system at various CaCO₃ doses using two alginate samples of different mannuronate (M)/guluronate (G) ratios but with comparable molecular masses. Macroscopic rheological properties of the polysaccharide were discussed during gelation in relation to microscopic supermolecular structures imaged by atomic force microscopy and Ca²⁺ binding. At fixed concentrations of the polysaccharide (0.5 w/v%) and glucono-δ-lactone (15 mM) as an acidic material, the G-rich sample was higher in elasticity with rod-like molecular assemblies at the highest CaCO₃ dose; 15 mM, while the M-rich sample was higher in elasticity with network-like molecular assemblies at the lowest CaCO₃ dose; 3.75 mM. Gelation behavior near the sol-to-gel transition was generally described by the percolation model, except for the M-rich sample at the lowest CaCO₃ dose. A critical CaCO₃ dose corresponded to 7.5 mM at which both alginate samples showed essentially the same gelation kinetics. In an equilibrium state, it was estimated that the G-rich sample was bound to larger amount of Ca²⁺ at the lowest CaCO₃ dose, while the M-rich sample was bound to larger amount of Ca²⁺ at the highest CaCO₃ dose. The amount of bound Ca²⁺ did not directly relate to elasticity of the system. Based on these results, dominant block structures are suggested for gelation.     

木素胺化改性制备重金属吸附剂

以木素为原料,通过胺化改性制备木素基重金属吸附剂,吸附Pb2+。实验中首先将木素用琥珀酸酐进行酸酐改性,然后以对甲苯磺酰氯为催化剂与三乙烯四胺反应,得到胺化改性木素。以琥珀酸酐与木素摩尔比及反应时间为变量优化酸酐改性条件。通过测定羧基含量、红外光谱分析(FT-IR)和吸附性能分析对产物性能进行表征。结果表明,琥珀酸酐与木素摩尔比1.5∶1、反应时间1 h、温度28℃、pH值8.5~9.0时,所得酸酐改性木素中羧基含量最高,达1.98 mmol/g;FT-IR谱图分析显示木素改性成功;胺化改性木素对Pb~(2+)吸附符合拟二阶动力学模型和Freundlich模型,同时随着pH值的升高,产物吸附性能随之提高,p H值5时吸附性能降低,在p H值为5时胺化改性木素对Pb~(2+)的吸附量达到152.95 mg/g。     

Molecular structure of La3+-induced methanol dehydrogenase-like protein in Methylobacterium radiotolerans

La(3+) and not Ca(2+) increases methanol dehydrogenase (MDH) activity in Methylobacterium radiotolerans NBRC15690. La(3+)- and Ca(2+)-MDH-like proteins were found to be homodimeric (α(2)) and heterotetrameric (α(2)β(2)), respectively. N-terminal amino acid sequences of these proteins revealed that La(3+)- and Ca(2+)-MDH-like proteins were encoded by xoxF and mxaFI, respectively.     

Phenol content related to antioxidant and antimicrobial activities of Passiflora spp. extracts

Methanolic extracts were prepared from different organs of plants from five Passiflora species obtained by zygotic embryo culture and evaluated for their capacity to quench DPPH and ABTS^•+ radicals in comparison to that of Trolox, a water soluble vitamin-E analogue. Moreover their antimicrobial activity against E. coli was tested by agar diffusion and turbidity assays. P. nitida, P. foetida, and P. palmeri showed antimicrobial activity. P. nitida and P. palmeri also showed high antioxidant activity. P. tenuifila and P. coriacea demonstrated antioxidant power but not antimicrobial activity. The phenolic content of the different extracts was studied and quantified by spectrophotometric methods, HPLC, and mass spectrometry. High antioxidant activity correlated with high amounts of o-diphenol and catechin. An unknown component, tentatively identified as structural isomer of isoschaftoside, appeared to correlate with antimicrobial activity.     

OCC造纸废水中微细胶黏物及Ca2+协同去除的研究

废旧箱纸板（OCC）造纸废水回用过程中面临着微细胶黏物沉积和因Ca²⁺浓度过高引起的厌氧颗粒污泥钙化两大难题。本研究对比评估了电絮凝法、物理法、化学法、生物酶法对模拟OCC造纸废水的处理效果;结果表明,电絮凝法能够更好去除OCC造纸废水中的微细胶黏物和Ca²⁺。在此基础上研究了电絮凝处理的最佳条件：铝为阳极材料,电流密度、电极间距和反应时间的最佳处理条件分别为115 A/m²、5 cm和60 min。在最佳条件下,经电絮凝处理后得到的絮凝体中,Al³⁺和Ca²⁺的相对含量高于对照组,表明电絮凝法能有效去除OCC造纸废水中的微细胶黏物、COD和Ca²⁺,且该方法绿色无污染,符合可持续发展的要求。