A Quencher-Based Blood-Autofluorescence-Suppression Strategy Enables the Quantification of Trace Analytes in Whole Blood

Precise quantification of trace components in whole blood via fluorescence is of great significance. However, the applicability of current fluorescent probes in whole blood is largely hindered by the strong blood autofluorescence. Here, we proposed a blood autofluorescence-suppressed sensing strategy to develop an activable fluorescent probe for quantification of trace analyte in whole blood. Based on inner filter effect, by screening fluorophores whose absorption overlapped with the emission of blood, a redshift BODIPY quencher with an absorption wavelength ranging from 600–700 nm was selected for its superior quenching efficiency and high brightness. Two 7-nitrobenzo[c] [1,2,5] oxadiazole ether groups were introduced onto the BODIPY skeleton for quenching its fluorescence and the response of H₂S, a gas signal molecule that can hardly be quantified because of its low concentration in whole blood. Such detection system shows a pretty low background signal and high signal-to-back ratio, the probe thus achieved the accurate quantification of endogenous H₂S in 20-fold dilution of whole blood samples, which is the first attempt of quantifying endogenous H₂S in whole blood. Moreover, this autofluorescence-suppressed sensing strategy could be expanded to other trace analytes detection in whole blood, which may accelerate the application of fluorescent probes in clinical blood test.     

Proof of class number formulae by machine

As an attempt to follow the direction of machine proof, a personal computer LE0386/25 is used to prove some class number formulae for certain imaginary quadratic number fields ,q=3, 7, 11, 19, 23, 31, 43 and 47) if the real quadratic number field has class number one for a primep = 4N ² + 1 (N is a positive integer). Project supported by the National Natural Science Foundation of China.     

Crystal and molecular structure of 3-chloro-3,6-dinitro-2,2-dimethyl-4-chromanone, C11H9N2O6Cl

3-Chloro-3,6-dinitro-2,2-dimethyl-4-chromanone is the first 3-chloro-3-nitro-4-chromanone to be synthesized by nitrating its corresponding 4-chromanone at the 3 position and then chlorinating the nitration product. Its structure was determined by IR, NMR, MS and x-ray crystallography. It crystallizes as a pair of enantiomers with 2 molecules in the primitive triclinic space group P (#2) with a = 9.476(2), b = 10.906(3), c = 6.578(5) Å, and = 101.08(3), = 90.13(3), = 73.23(1)°, V = 637.7500 ų, and Z = 2. The nitro group at the 6 position conjugates with the benzene ring. The pyranone ring has a half-chair conformation; the chloro group occupies the pseudoequatorial position, and the nitro group occupies the pseudoaxial position. The 2 and 3 positions are essentially antiperiplanar, minimizing steric interaction.     

在三乙酸锰引发下芳烃与β-二羰基化合物的反应

在三乙酸锰和磷酸作用下,芳烃和乙酰乙酸乙酯反应,生成芳基乙酰乙酸乙酯和亚芳基二乙酰乙酸乙酯。反应是通过生成CH_3COCHCO_2C_2H_5自由基进行的。丙二酸二乙酯和芳烃在三乙酸锰和磷酸作用下也能发生同样的反应。     

银离子对DNA碱基对的横向电输运特性的影响

以密度泛函理论为基础,利用非平衡格林函数方法研究DNA的两碱基对分别与Au电极耦合的两电极体系的电输运特性.首先计算电极-碱基对间距对碱基对横向输运性质的影响,发现碱基对的电导对距离的变化非常敏感,呈剧烈的振荡变化.然后在电极距离固定的情况下,计算系统在低偏压下的横向传输特性,并对与银离子结合前后的碱基对的横向传输特性进行比较.结果发现,加入银离子后,G-C碱基对的导电能力下降,A-T碱基对的电导增大.     

可利用酸碱控制的分子器件：准轮烷的“开”与“关”

4,4‘－二氨基二苯醚衍生物（A）和缺电子联吡啶大环（CPQT）发生π-π堆积作用进行自组装形成准轮烷;准轮烷的“开”与“关”可以利用酸碱调控。此过程可利用体系的氢的化学位移变化来进行跟踪。     

MCA-Donnan模型对重金属吸附的应用进展

Koopal等荷兰、英国和法国的学者在对腐殖酸吸附重金属研究提出了NICA-Donnan模型,它提出质子结合和金属离子结合的相关性,以扩展Henderson-Hasselbalch模型或Hill模型作为局部吸附等温模型,采用连续亲和分布解释了吸附剂异相性,并引入Donnan模型来解释非特异吸附和静电吸附.NIcA-DPonnan模型具有很大灵活性和适应性,在环境科学领域得到广泛应用.     

Serial mixed-mode cation- and anion-exchange solid-phase extraction for separation of basic,neutral and acidic pharmaceuticals in wastewater and analysis by high-performance liquid chromatography–quadrupole time-of-flight mass spectrometry

A novel solid-phase extraction (SPE) method is presented whereby 15 basic, neutral and acidic pharmaceuticals in wastewater were simultaneously extracted and subsequently separated into different fractions. This was achieved using mixed-mode cation- and anion-exchange SPE (Oasis MCX and MAX) in series. Analysis was performed by high-performance liquid chromatography–quadrupole time-of-flight mass spectrometry (HPLC/QTOF-MS). A fast separation was achieved, with all compounds eluting within 6 min, narrow chromatographic peaks, with a peak base width of 6 s on average, and a high mass accuracy of quantified wastewater sample ions, with average mass errors in absolute value of 0.7 mDa or 2.7 ppm. The recovery of the SPE method in the analysis of sewage treatment plant (STP) influent and effluent wastewater was on average 80% and the ion suppression 30%. For less demanding samples Oasis MCX used alone may be an alternative method, although for STP influent waters containing high loads of organic compounds the clean-up achieved using only Oasis MCX was insufficient, leading to unreliable quantitation. Furthermore, serial SPE separation according to molecular charge added an additional degree of analyte confirmation. For quantitation, an approach combining external standard calibration curves, isotopically labelled surrogate standards and single-point standard addition was used. The applicability of the method was demonstrated in the analysis of influent and effluent wastewater from an STP, using small sample volumes (25–50 mL). The effluent wastewater had been subjected to three different treatments; activated sludge, activated sludge followed by ozonation, and a membrane bioreactor (MBR). Ozone treatment proved superior in removal of the analysed pharmaceuticals, while the MBR provided higher removal efficiencies than the activated sludge process.     

Liquid chromatography/mass spectrometry analysis of perfluoroalkyl carboxylic acids and perfluorooctanesulfonate in bivalve shells: Extraction method optimization

Different extraction methods, including extraction by organic solvents with and without acetic acid digestion, and mixed inorganic acid digestion coupled with solid phase extraction (SPE), were developed for the analysis of perfluorinated carboxylic acids (PFCAs) and perfluorooctanesulfonate (PFOS) in bivalve shells. The extracts were separated, identified and quantified by liquid chromatography–electrospray ionization–tandem mass spectrometry (LC–ESI–MS/MS). The method utilizing mixed acid digestion coupled with SPE performed more efficiently than other extraction methods. Matrix recoveries of the optimized methods ranged from 92% to 104%, with limits of detection of 0.05–0.43 ng/g. The optimized method was successfully applied to the analysis of PFCAs and PFOS in shell samples of two bivalves from Bohai Bay, China. PFCAs and PFOS concentrations in the shells ranged from 0.3 ng/g to 4.1 ng/g, 1–50 times lower than those in the soft tissues of bivalves for most target analytes. No relationship between PFCAs and PFOS in shells and in soft tissues was found; this is explained by the different contaminant uptake mechanism of shells and soft tissues.