微量酸微波消解-原子荧光光谱法同时测定食品中砷、汞

为建立同时测定食品中砷、汞微量酸微波消解-原子荧光光谱法,采用1ml硝酸 0.5ml过氧化氢 6ml水的微波消解体系,用0.5g抗坏血酸 1g硫脲为As5 预还原剂,消解液无需赶酸,直接用原子荧光光谱仪同时测定。砷在0～200ng/ml、汞在0～40ng/ml范围内线性关系良好,相关系数均大于0.9995。方法的检出限砷0.12ng/ml、汞0.04ng/ml。检测国家标准物质GBW08508米粉、GBW08513茶树叶,相对标准偏差砷3.94%,汞3.22%,平均回收率砷96.1%;汞93.6%。该方法试剂用量少,污染小,简便、快速、准确,能满足各类食品中砷、汞检测。     

银纳米簇介导的荧光传感器在重金属离子检测中的应用

重金属离子作为一类环境污染物，常存在于空气、土壤和水体中，由于其易在生物体内富集、难以降解，严重威胁了人类健康，因而成为环境污染和食品安全等领域的重要检测指标。目前，用于检测重金属离子的方法主要有电感耦合等离子体质谱法、原子吸收光谱法等，然而这些方法需要复杂的仪器设备、较长的实验耗时，以及较高的操作要求，具有一定的局限性。因此，开发快速、灵敏、简便的重金属离子检测方法越来越受到研究人员的重视。银纳米簇（AgNCs）作为一种新型纳米材料，具有良好的荧光特性，其介导的荧光生物传感器可以应用于重金属离子的快速检测，并且具有高灵敏性和特异性。本文综述了以不同分子为模板合成的AgNCs，以及其介导的荧光生物传感器在单一和多种重金属离子检测方面的最新研究进展，阐述了AgNCs今后仍需深入研究的部分，并对其发展前景进行了展望。     

Stratification of connective tissue toughness in beef roasts assessed by simultaneous fluorometry and penetrometry

Beef rib roasts were probed to measure connective tissue fluorescence and resistance to penetration at different depths. Data were collected at the aponeurosis on the surface of Longissimus thoracis (site 1), from muscle below the aponeurosis (site 2), and from a major perimysial septum within the muscle (site 3). Penetration force at site 1 was correlated with forces at site 2 (r = 0.51, P < 0.05) and site 3 (r = 0.63, P < 0.025). Fluorescence at site 1 was correlated with fluorescence at site 2 (r = 0.81, P < 0.0005) and at site 3 (r = 0.78, P < 0.005). Thus, the aponeurosis on the muscle surface is related to underlying connective tissues in strength and composition. Aponeurosis was more than three times as strong as muscle alone (P < 0.001). Failure to detect a useful relationship between aponeurosis fluorescence and strength was attributed to loss of linearity (optical saturation) as the aponeurosis wrapped around the probe.     

Chemical, physical and spectroscopic characterization of Posidonia oceanica (L.) Del. residues and their possible recycle

Posidonia is an endemic marine plant of the Mediterranean Basin forming wide grasslands involved in the oxygenation of seawaters, fauna protection and littoral erosion prevention. Starting from September-October, leaves and part of rhizomes detach off the marine plant and reach the beaches. Onshore residues represent a great environmental, economical, social and hygienic problem in all coastal zones of Mediterranean Basin because of the great disturb to the bathers and population, and the high costs for their removal and disposal to landfill.Authors characterized the onshore residues by means of physical, chemical and spectroscopic analyses in order to propose alternative solutions to the landfill and to reutilize them in agricultural applications as well as a source of energy.Physical, chemical and spectroscopic features of posidonia residues indicated a possible utilization in agriculture in their raw state. In facts, provided a reduction in the electrical conductivity and Na content, plant residual materials may be directly used as growing media or appropriately composted with raw materials of different provenance and basically opposite characteristics. In particular, the fibrous debris showed features similar to a bulking agent, while the leaves residues closely resembled a green waste. The fibrous portion of posidonia residues can be also utilized as biofuel according to their lower heating values (LHV) ranging between 13.6 and 15.7 MJ kg⁻¹, whereas leaves debris are not so suitable for the energy recovery because their LHV were around 10 MJ kg⁻¹.     

Biosynthesis of proteins containing modified lysines and fluorescent labels using non-natural amino acid mutagenesis

The preparation of posttranslationally modified proteins is required to investigate the function and structure of modified proteins. However, homogeneously modified proteins are not easily isolated from natural sources or prepared using modification enzymes. Non-natural amino acid mutagenesis has enabled us to incorporate modified amino acids into specific positions of proteins in both cell-free and in-cell translation systems using tRNAs that are aminoacylated with modified amino acids. Here, we developed a method of double incorporation of modified amino acids and fluorescent non-natural amino acids in a quantitative, position-specific manner to obtain modified and fluorescently labeled proteins. To introduce methyllysine, dimethyllysine, trimethyllysine, and acetyllysine, frameshift and amber suppressor tRNAs aminoacylated with modified lysines were synthesized by chemical aminoacylation and supplied to an Escherichia coli cell-free translation system. The immunodetection of the translation products indicated that the modified lysines were incorporated into streptavidin and histone H3 in a quantitative, position-specific manner. Calmodulin derivatives containing a fluorescent non-natural amino acid at the N-terminal region and modified lysines at the Lys115 position were also synthesized, and their binding activity to a calmodulin-binding peptide was analyzed by fluorescence correlation spectroscopy. The results obtained here demonstrate that this method is useful in preparing and analyzing naturally occurring and non-natural modified proteins.     

Cu(II) complexation of high molecular weight (HMW) fluorescent substances in root exudates from a wetland halophyte (Salicornia europaea L.)

High molecular weight (HMW) fractions are important components in root exudates. However, there is little available information concerning complexation of Cu(II) to the HMW fractions in root exudates. In the present study, complexation of root exudates from Salicornia europaea L. with Cu(II) was investigated using excitation emission matrix (EEM) fluorescence spectroscopy. Two protein-like fluorescence peaks were identified in the EEM spectra of root exudates. Fluorescence of both peaks was clearly quenched by Cu(II). The increase of conditional stability constant with increasing temperature indicates that the fluorescence quenching of the protein-like fluorescence by Cu(II) may be controlled by a dynamic process. The values of conditional stability constants (logK(a)) were in the range of 4.32-4.69, which were close to those of complexation of fulvic acid with Cu(II). This shows that the HMW fluorescent substances in root exudates from S. europaea L. were strong organic ligands for Cu(II). Our study suggests that the HMW fluorescent substances may affect chemical forms, mobility, and thus the fate of copper in wetland.     

TaqMan探针法实时荧光定量PCR快速检测沙门菌的探讨

为建立一种快速、灵敏、特异的实时荧光定量PCR法用于沙门菌的检验，根据GenBank上登录的编号为AE016841的沙门菌序列，应用生物学软件在fimY基因的保守区设计引物和TaqMan探针，同时应用BLAST程序进行网上序列比对，并进行筛选、优化。用鼠伤寒标准菌和60份食品样本进行本检测方法的特异性、敏感性和重复性试验，并与常规法和科玛嘉平板分离法做比较。本方法对沙门菌的检测具高度的特异性，检测的灵敏度这102CFU／ml，从增菌至完成检测仅需24h左右，是一种快速检测沙门菌的敏感、特异的新方法。     

Determining the geographic origin of Emmental cheeses produced during winter and summer using a technique based on the concatenation of MIR and fluorescence spectroscopic data

A technique that used multivariate data analysis to combine mid-infrared (MIR) spectroscopy with front-face fluorescence spectroscopy was used to discriminate between Emmental cheeses originating from different European countries: Austria (n=12), Finland (n=10), Germany (n=19), France (n=57), and Switzerland (n=65). In total, 163 Emmental cheeses produced in winter (n=91) and summer (n=72) periods were investigated. When Factorial Discriminant Analysis was applied to either the infrared or fluorescence spectral data the classifications were not satisfactory. Therefore, the first twenty principal components (PCs) of the PCA extracted from each data set (MIR and tryptophan fluorescence spectra) were pooled (concatenated) into a single matrix and analysed by Factorial Discriminant Analysis. Correct classifications were obtained for the samples for 89% of the calibration spectra and 76.7% of the validation spectra. The discrimination for cheeses from Finland was excellent, while Austrian, German, French and Swiss cheeses were also discriminated well although a few samples were misclassified. It was concluded that concatenation of the data from the two spectroscopic techniques is an efficient technique for authenticating Emmental cheeses independently of their manufacturing period.     

Electrochemical polymerization of an electron deficient fluorene derivative bearing ethylenedioxythiophene side groups

A new low band gap polyfluorene derivative, poly(2,7-bis-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)-fluoren-9-one) (PEFE), containing ethylenedioxythiophene as donor and fluorenone (FO) as an acceptor groups was electrochemically synthesized. Electrochemical polymerization of 2,7-bis-(2,3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)-fluoren-9-one (EFE) was achieved in dichloromethane with 0.1 M tetrabutylammonium-hexafluorophosphate both via and potentiostatic methods. The polymer was characterized by cyclic voltammetry, UV-vis, FT-IR and NMR spectroscopic techniques. Spectroelectrochemical and electrochemical analysis revealed that the polymer film is both p- and n-dopable and can be successfully cycled and switched between its neutral and oxidized/reduced states. Furthermore, PEFE shows electrochromic behavior by a color change from brown to blue with a switching time of 1.65 s during oxidation with a high coloration efficiency (250 cm²/C). Fluorescence studies were also performed.