Determination of Microamouts of Ammonia in Meat by Nessler's Reagent Spectrophotometry

本文提出了一种测定肉中粗氨的方法,可用于肉品新鲜度的检验。在常温下,纳氏试剂与肉中粗氨反应生成淡红棕色胶态化合物,最大吸收波长为400nm,表观摩尔吸光系数为1.404×104L/mol·cm,线性方程为y=0.52x+0.0001,r=0.9997,线性范围为0～1.0μg/ml,回收率在97.8%～104.8%之间。A method for the determination of the crude ammonia in meat was presented in this paper. The method based on the color reaction of ammonia-Nessler's Reagent in room temperature. The results showed that the apparent molar absorptivity is 1.404 ×104 L/mol·cm at the wavelength of 400nm. Beer's law is obeyed for the ammonia in the range of 0～1.0 μg/ml. The correlation coefficient is 0.9995. The recovery rate is 97.8%～104.8%. The method has been applied satisfactorily to crude ammonia in meat.福建省科技计划重点项目(2004Y012

Determination of Lead Content in Standard Materials of Lake Sediment and Tea by ID-ICP-MS

采用2种微波消解体系(HNO3-H2O2和HNO3-H2O2-HF)及3种定量模式(同位素稀释法、标准工作曲线法和标准加入法),对沉积物和茶叶标准物质中的铅进行测定,结果表明:同位素稀释质谱法的各项检测指标显著优于其它两种定量模式(茶叶中铅含量测定值为4.30μg/g),标准加入法次之(3.75μg/g),标准工作曲线法较差(3.61μg/g)。二种微波消解体系中,加HF酸优于不加HF酸,不加HF,茶叶中铅的回收率仅有89%,加入HF则上升为98%。Three different quantitative modes,namely external calibration,standard addition and isotope diluˉtion were compared for the determination of lead contents in lake sediment and tea standard materials with two digestion systems.The results showed that the isotope dilution gave the highest accuracy and precision in comˉparison with the other two modes.But the results were affected by the digestion system.For example,the reˉcoveries of lead content for tea were98%and89%for HNO 3 -H 2 O 2 -HF and HNO 3 -H 2 O 2 digesting sysˉtem,respectively.福建省重大科技项目子课题(2003Y005-04);; 厦门大学现代分析科学教育部重点实验室开放课题(B40402

Studies on activity of pork peroxidase using TMB

以3,5,3,′5′-四甲基联苯胺(TMB)为底物对猪肉过氧化物酶(POD)的酶学特性以及猪肉不同部位过氧化物酶活性水平进行了较为系统的研究,并以辣根过氧化物酶(HRP)为标准酶获得了酶活性标准曲线。猪肉过氧化物酶在温度38℃,pH 4.80时活性最高。酶浓度与酶反应初始阶段的酶活性有较好的线性关系,氢供体底物TMB的最佳浓度为2.80×10-4mol/L,浓度过大则会抑制酶的活性,氢受体底物过氧化氢的浓度与酶活性有较好的线性关系和较宽的线性范围(0~4.20×10-3mol/L)。猪肉不同部位如腰条(指外腰条)、里脊(指内腰条)、后腿、前腿、三层、腱子中POD活性大小不同,前三者的POD活性相近且活性较小,而后三者活性较为相近且活性较大。通过辣根过氧化物酶标准曲线可以求估待测样品中POD的活性值。The pork peroxidase(POD) and its activity in different parts of pork using 3,5,3′,5′-tetramethylbenzidine(TMB) were detected and studied.The POD activity was evaluated using horseradish peroxidase(HRP) as a standard enzyme.The pork POD kept its best activity at the temperature of 38 ℃ and pH of 4.80,respectively.The concentration of POD was linear with the POD activity at the initial stages of enzyme reaction.The optimal concentration of TMB for POD activity measurement was 2.80×10-4 mol/L,and the activity would be inhibited if the concentration of TMB was over the value.The concentration of H2O2 was also linear with the POD activity and the linear range was 0～4.20×10-3 mol/L.The POD activities of the pork in the part of outer-tenderloin,inner-tenderloin and hind leg nearly kept the same and lower than those of the part of foreleg,streaky pork and tendon.The activity value of sample could be estimated according to the standard curve of HRP.福建省科技计划重点(2004Y012)项目资

Fine root morphology of different branch orders of three dominant subalpine tree species in western Sichuan

林木细根(直

Assembled 3D cell niches in chitosan hydrogel network to mimic extracellular matrix

 Extracellular matrix (ECM) is a composite material which contains a complex mixture of fibrous proteins and heteropolysaccharides, providing an important model for designing biomaterials. To mimic ECM, we fabricated 3D cell niches in chitosan hydrogel network via the layer-by-layer (LbL) molecular self-assembly method. Compression modulus of genipin-crosslinked chitosan hydrogel could be regulated from 0.014 +/- 0.003 MPa to 0.24 +/- 0.009 MPa as chitosan concentration increased from 1 wt.% to 5 wt.%, which reached the requirements of soft tissue. The 10 mu m CaCO3 microparticles as porogens were embedded into hydrogel network to resemble in vivo 3D microstructure. Porosity could be modulated from 32.10 +/- 5.08% to 91.41 +/- 6.56% as more CaCO3 microparticles embedded. The ECM component of chondroitin sulfate (CS) was layer-by-layer assembled into hydrogel network via electrostatic interactions between negative-charged CS molecules and positive-charged chitosan molecules. Subsequently, the process of delivering fibroblast growth factor (FGF) in hydrogel network could be precisely controlled due to CS molecules' affinity interactions with FGF. In vitro 3D cell culture experiments revealed that human lung fibroblast (HLF) grew better in the scaffolds as fabricated than that in untreated chitosan hydrogel. These results suggest adaptive 3D cell niches can be fabricated through molecular self-assembly of the ECM components for engineering the aimed tissues. (C) 2013 Elsevier B.V. All rights reserved

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel