Cascade Rearrangement: Nitro Group-Participating Syntheses of 1,2,5-Thiadiazoles and 1,2,4-Thiadiazolones.

A trifluoroacetic anhydride-mediated cascade process for the synthesis of thiadiazole derivatives is described. 1,2,5-Thiadiazoles and 1,2,4-thiadiazolones could be obtained by variation of the reaction conditions. A group of functionalized thiadiazole derivatives were synthesized in moderate to good yields from nitro-group-containing N-tert-butanesulfinamides. The reactions involved in this tandem process are a Pummerer-like rearrangement of the tert-butanesulfinamide unit, a nitrile oxide formation via nitro group rearrangement, addition of oxygenated nucleophiles, and an N-S bond forming cyclization followed by concomitant elimination.

Urea detection in milk by urease-assisted pH-sensitive carbon dots.

Excessive urea in milk will lead to serious health problems. To detect whether the urea concentration in milk exceeds the standard and ensure the quality of milk, it is necessary to develop detection technology for urea in milk. But it is difficult to detect urea in milk conveniently and accurately by traditional methods. To measure the concentration of urea in milk, stable green light carbon dots (CDs) were synthesized by a one-step method as a fluorescent probe. Then, 3, 5-diaminobenzoic acid was used as the precursor for CD synthesis. Experimental results showed that CDs can generate strong fluorescence when excited by light (350-450 nm). The fluorescence peak wavelength is 490 nm, and the optimum excitation wavelength is 390 nm. The fluorescence intensity of CDs has a significant change with variations of pH (pH of 6-9), and the higher the pH, the lower the fluorescence intensity. Additionally, urea can be hydrolyzed by urease to produce ammonia and carbon dioxide. Ammonia is ionized in water to produce OH-, which increases the pH of the solution. After adding standard urea to milk, urease and CDs are added. The fluorescence intensity of CDs in the mixed solution decreases as the concentration of standard added urea increases. Thus the concentration of urea in milk can be calculated. The experimental results show that the CD method for detecting urea in milk has advantages of high sensitivity and wide measurement range. The linear interval is 25-500 mg/L, R2 is 0.998, and the limit of detection is 6.27 mg/L. The concentration of urea in the milk used in the experiment is 265.46 mg/L. CDs are easy to fabricate, and the advantages of the method are simple operation, no pretreatment, safety, and low cost. A new method for the detection of urea in milk was established, to the best of our knowledge, and this method can aid in food quality control.

[The Study of Three-Dimensional Synchronous Fluorescence Spectral Characteristics of Liuwei Dihuang Pills].

Three-dimensional synchronous fluorescence of each component of Liuwei dihuang pills (Prepared rehmannia root, cornel, yam, alisma, poria cocos, and cortex moutan) is measured by using FLS920P fluorescence spectrometer. Feature parameters were extracted. It can be found that each component is fluorescent material and the lines are all different. Furthermore, Three-dimensional synchronous fluorescence of Liuwei dihuang pills boiling with standard water and non-standard water are all measured and there are significant differences between them. It can be applied in distinguishing different formula of Chinese medicine decoction. Experimental and Theoretical conclusion show that: the three-dimensional fluorescence spectrometry method and the combination of synchronous fluorescence spectroscopy method can further improve the sensitivity and selectivity of fluorescence spectroscopy, have a distinct advantage in a complex multi-component mixture of fluorescence spectroscopic analysis. The study can provide a convenient and reliable method for establishing a complete fingerprint of Chinese traditional medicine. It also can help identifying the component and the quality of Chinese patent medicine.

[Year Discrimination of Mild Aroma Chinese Liquors Using Three-Dimensional Fluorescence Spectroscopy Combined with Parallel Factor and Neural Network].

Three-dimensional fluorescence spectroscopy coupled with parallel factor analysis and neural network was applied to the year discrimination of mild aroma Chinese liquors. The excitation-emission fluorescence matrices (EEMs) of 120 samples with various years were measured by FLS920 fluorescence spectrometer. The trilinear decomposition of the data array was performed and the loading scores of and the excitation-emission profiles of four components were also obtained. The scores were employed as the inputs of the BP neural networks and the PARAFAC-BP identification model was constructed. 10 samples were collected from 10, 20 and 30 years of liquors respectively, and 30 samples were selected as the test sets. The remaining 90 samples were used as the training sets to build the training model. The year prediction of unknown samples was also carried out, and the prediction accuracy was 90%, 100% and 100%, respectively. Meanwhile, the discrimination analysis method and the multi-way partial least squares discriminant analysis were compared, namely PARAFAC-BP and NPLS-DA. The results indicated that parallel factor combined with the neural network (PARAFAC-BP) has higher prediction accuracy. The proposed method can effectively extract the spectral characteristics, and also reduce the dimension of the input variables of neural network. A good year discrimination result was finally achieved.

Engineering Photosystem I Complexes with Metal Oxide Binding Peptides for Bioelectronic Applications.

Conventional dye-sensitized solar cells comprise semiconducting anodes sensitized with complex synthetic organometallic dyes, a platinum counter electrode, and a liquid electrolyte. This work focuses on replacing synthetic dyes with a naturally occurring biological pigment-protein complex known as Photosystem I (PSI). Specifically, ZnO binding peptides (ZOBiP)-fused PSI subunits (ZOBiP-PsaD and ZOBiP-PsaE) and TiO2 binding peptides (TOBiP)-fused ferredoxin (TOBiP-Fd) have been produced recombinantly from Escherichia coli. The MOBiP-fused peptides have been characterized via western blotting, circular dichroism, MALDI-TOF, and cyclic voltammetry. ZOBiP-PSI subunits have been used to replace wild-type PsaD and PsaE, and TOBiP-Fd has been chemically cross-linked to the stromal hump of PSI. These MOBiP peptides and MOBiP-PSI complexes have been produced and incubated with various metal oxide nanoparticles, showing increased binding when compared to that of wild-type PSI complexes.

[Quantum Chemistry Calculation of Ponceau 4R Molecule Structure and Research on the Fluorescence Mechanism].

The molecule structures of Ponceau 4R in ground state and the excited state were optimized by employing the Gaussian 09W program package. In addition, the electronic structure and frontier orbital of the ground state, the emission wavelength of the excited state was also investigated. And then, the Edinburgh FLS920P fluorescence spectrometer was applied to the measurement of the fluorescence spectra of cochineal solution, and the emission spectra was obtained. The calculated emission wavelength had a good coincidence with the experiment data, which indicates that the optimized structures mentioned above are reasonable. The structures comparison between the ground state and the excited state was also performed to analyze the mechanism of fluorescence spectrum. It can be concluded that the molecule structure of excited state is nearly planar, so Ponceau 4R is thought to have strong fluorescent characteristics, the emission fluorescence is the result of transition from orbit 139 to orbit 137.

Residual amount of HBV DNA in serum is related to relapse in chronic hepatitis B patients after cessation of nucleos(t)ide analogs.

OBJECTIVE: To investigate the relationship between relapse and the levels of the residual amount of HBV DNA in serum at cessation in chronic hepatitis B patients meeting 2008 Asian Pacific Association for the Study of the Liver (APASL) nucleos(t)ide analogs (NAs) cessation criteria. METHODS: A total of 72 chronic hepatitis B patients who took NAs and had reached 2008 APASL cessation criteria entered the study. Patients were followed up for 6 months or longer after antiviral therapy was stopped. Serum HBV DNA level at cessation was detected by a highly sensitive polymerase chain reaction assay with detection limitation of 2 IU/mL. RESULTS: Of all the 72 patients, 42 patients (65.3%) relapsed after NA cessation. The detectable rate of the trace amount of HBV DNA at cessation was 41.7% by highly sensitive polymerase chain reaction reagents. The detectable rate of patients with consolidation treatment duration of <18 months was higher than that with consolidation duration of ≥18 months (47.5% vs. 15.4%, P=0.034), and the detectable rate of patients with HBeAg seroconversion within 6 months of treatment was lower than that of ≥6 months (25.0% vs. 61.5%, P=0.036). The residual amount of HBV DNA and detectable rate at cessation showed significant differences between relapsed and nonrelapsed patients (130.4±420.90 vs 44.6±155.16 IU/mL, P=0.004; 55.3% vs. 16.0%, P=0.001). The cutoff value predicting relapse was 2.24 IU/mL, with a sensitivity of 0.553 and specificity of 0.840. CONCLUSIONS: Residual amount of HBV DNA in serum at NA cessation is associated with HBV relapse. The cutoff value predicting relapse was 2.24 IU/mL, with a sensitivity of 0.553 and specificity of 0.840.

Determination of components of mixed color solutions by fluorescence spectroscopy combined with calibration algorithms.

The three-dimensional spectra of mixed solutions of allure red, sunset yellow and brilliant blue were obtained. Then the three synthetic food colors were determined by parallel factor analysis (PARAFAC) and alternating trilinear decomposition (ATLD) algorithms, respectively. The component number of model is three by core-consistency diagnostic. The average recoveries of allure red, sunset yellow and brilliant blue obtained by PARAFAC were 98.75% +/- 8.9%, 97.22% +/- 2.9% and 99.00% +/- 2.9% and those by ATLD algorithm were 99.78% +/- 5.9%, 92.52% +/- 5.5% and 97.23% +/- 5.8%, respectively. Results show that both of the algorithms can be used in direct and rapid determination of multi-components of mixtures. From further comparison, the PARAFAC is more stable and advantageous.

Molecular interactions between photosystem I and ferredoxin: an integrated energy frustration and experimental model.

The stromal domain (PsaC, PsaD, and PsaE) of photosystem I (PSI) reduces transiently bound ferredoxin (Fd) or flavodoxin. Experimental structures exist for all of these protein partners individually, but no experimental structure of the PSI/Fd or PSI/flavodoxin complexes is presently available. Molecular models of Fd docked onto the stromal domain of the cyanobacterial PSI site are constructed here utilizing X-ray and NMR structures of PSI and Fd, respectively. Predictions of potential protein-protein interaction regions are based on experimental site-directed mutagenesis and cross-linking studies to guide rigid body docking calculations of Fd into PSI, complemented by energy landscape theory to bring together regions of high energetic frustration on each of the interacting proteins. The results identify two regions of high localized frustration on the surface of Fd that contain negatively charged Asp and Glu residues. This study predicts that these regions interact predominantly with regions of high localized frustration on the PsaC, PsaD, and PsaE chains of PSI, which include several residues predicted by previous experimental studies.

Accurate and efficient characterization of streak camera using etalon and fitting method with constraints.

Streak camera is widely used in continuous time diagnostics in fast physical process. To produce accurate result, it requires delicate calibration and a reliable analysis method. High quality sweep-rate data with uncertainty smaller than 0.5% are obtained over the full record area by a constrained fitting method of peak position measurement, with a short pulse laser and an etalon as the fiducial source. The temporal response is linearized by this full-screen sweep-rate data, which eliminates errors in measurement due to nonlinearity and space-distortion inherent in streak camera.

[Study on saltation of fluorescence excitation spectra of erythrosine].

The fluorescence excitation spectra and absorption spectra of six kinds of erythrosine solutions with concentrations of 10, 20, 30, 40, 50 and 60 microg x mL(-1) were experimentally measured. It was found that the fluorescence excitation peaks are both located at 530 nm significantly when the concentrations of erythrosine solutions are 10 and 20 microg x mL(-1). However, the linetype saltation of fluorescence excitation spectrum occurs as the concentration of erythrosine solution is above 30 microg x mL(-1). The valley is located at 530 nm and two new peaks appear at both flanks of the valley. Compared with fluorescence excitation spectra, the absorption spectra of erythrosine solutions are without saltation and the peaks are all located at 530 nm. According to calculations and a series of contrast experiments, it was demonstrated that the absorption characteristic of erythrosine and the spectral measurement mode conspire to cause the saltation of fluorescence excitation spectra. The results can provide guidance for further research on physical and chemical properties of erythrosine, and offer help and reference for study on saltation behavior in fluorescence excitation spectra and improvement in spectral measuring mode.

One-dimensional space resolving flat-field holographic grating soft x-ray framing camera spectrograph for laser plasma diagnostics.

A 1D space resolving x-ray spectrum diagnostic system has been developed to study the radiation opacity of hot plasma on SG-II laser facility. The diagnostic system consists of a 2400 lines/mm flat-field holographic grating and a gated microchannel plate coupled with an optical CCD and covers the wavelength range of 5-50 Å. The holographic grating was compared with a ruled one by measuring the emission spectra from a laser-produced molybdenum plasma. The results indicate that the holographic grating possesses better sensitivity than the ruled grating having nearly similar spectral resolution. The spectrograph has been used in radiative opacity measurement of Fe plasma. Simultaneous measurements of the backlight source and the transmission spectrum in appointed time range in one shot have been accomplished successfully with the holographic grating spectrometer. The 2p-3d transition absorption of Fe plasma near 15.5 Å in has been observed clearly.

[Comparative study on UV fluorescence characteristics of Su liquor].

In the present paper, the authors studied Guoyuan and Yanghe which are the most representative types of Su liquor. The authors got the three-dimensional fluorescence spectra of the liquor and analyzed their unique characteristics. Guyuan has obvious characteristics of the fluorescence in the 280-400 nm excitation wavelength range, including a major peak of fluorescence. Yanghe contains five clear fluorescence peaks in the 200-450 nm range of excitation wavelength. The two series of liquor have clear fluorescent characteristics in the 310-350 nm range of excitation wavelength, The range includes some organic compounds which play a decisive role in taste and flavor of Su liquor. The result of research provides a scientific basis for improving the mixing process of Su liquor and enhancing the quality of liquor.

Note: X-ray streak camera sweep speed calibration.

X-ray streak cameras are extensively used to study transient x-ray processes in experiments carried out on various laser facilities at the Research Center of Laser Fusion. Precise calibration and clear description of the sweep speed of the x-ray streak camera are vital for obtaining precise temporal information to understand the fast physics phenomena. An x-ray streak camera named wide-slit x-ray streak camera has been calibrated using a small-scale laser facility with pulse duration of 8 ps. Sweep speeds on most part of the output screen (charge coupled device) are obtained. These calibration results can be used to correct the nonlinearity of sweep speed in measurement of temporal processes.

[Determination and identification of synthetic food colors based on fluorescence spectroscopy and radial basis function neural networks].

Taking ponceau 4R and amaranth as an example, concentration prediction and kind identification of synthetic food colors by fluorescence spectroscopy and radial basis function neural networks are introduced. By using SP-2558 multifunctional spectral measuring system, the fluorescence spectra were measured for solution of ponceau 4R and amaranth excited respectively by the light with the wavelength of 300 and 400 nm. For each sample solution of ponceau 4R, 15 emission wavelength values were selected. The fluorescence intensity corresponding to the selected wavelength was used as the network characteristic parameters, and a radial basis function neural network for concentration prediction was trained and constructed. It was employed to predict ponceau 4R solution concentration of the three kinds of samples, and the relative errors of prediction were 1.42%, 1.44% and 3.93% respectively. In addition, for solution of ponceau 4R and amaranth, the fluorescence intensity corresponding to the fluorescence wavelength was used as the network characteristic parameters, and a radial basis function neural network for kind identification was trained and constructed. It was employed to identify the kind of food colors, and the accuracy is 100%. These results show that the method is convenient, fast, and highly accurate, and can be used for the detection of synthetic food color in food safety supervision and management.

[Quantitative determination of melamine by fluorescence spectroscopy and radial basis function neural networks].

Based on the experimental study, it was found that melamine solution excited by UV light can generate a strong fluorescence. The fluorescence spectrum is within a range from 310 to 600 nm, the peak wavelength of the fluorescence is about 420 nm, and the relationship between fluorescence intensity and melamine solution concentration is nonlinear. A method for the determination of melamine solution concentration was presented, which was based on fluorescence spectroscopy and radial basis function neural networks. For each sample, 30 emission wavelength values were selected, the fluorescence intensity corresponding to the selected wavelength was used as the network data, and a radial basis function neural network was trained and constructed. The trained radial basis function neural network was employed to predict the melamine solution concentration in five kinds of samples, and the relative errors of the results were 0.93%, 0.09%, 0.31%, 1.55% and 4.61%, respectively. The results show that this method can determine the content of melamine quickly and accurately. The whole research outcomes will provide a new method for determining the content of melamine and food safety supervision.

[Application of three-dimensional fluorescence spectra technique to discrimination of distilled spirits based on support vector machines].

In order to study the identifying and classification method of distilled spirits, about 100 kinds of normative distilled spirits were selected as the laboratory samples and their fluorescence spectra induced by ultraviolet light were measured by Roper-Scientific SP-2558 respectively. Then, using the statistics and plot software Origin 7.5, the authors composed the three-dimensional fluorescence spectra of the distilled spirits. In the meanwhile, the three-dimensional fluorescence spectra of the dis tilled spirits were also studied respectively. The authros compared the three-dimensional fluorescence spectra of different distilled spirits with the same brands and that of different spirits with the same brands. The authors are very confident that there must be some typical parameters, by which the authors can distinguish different kinds of distilled spirits with different brands effectively. And the authors found that while the three-dimensional fluorescence spectra of different distilled spirits with different brands are definitely different by their three typical parameters including the number of the major summit, position of the major summit and optimum wavelength, the three typical parameters of the three-dimensional fluorescence spectra of different distilled spirits with the same brand are very similar. Finally, the authors extracted the three typical parameters that are the number of the major summit, position of the major summit and optimum wavelength. Then, the data were processed by computer for emulation. As a result, the authors found that, using the three characteristic parameters, different kinds of distilled spirits can be classified ac curately by the algorithm of LS-SVM (least-squares support vector machine). The outcomes of the data emulated by different algorithms were obtained seriatim. The authors compared the outcomes, and the fact proved that more accurate outcome of identifying and classification can be obtained by LS-SVM.

[Fluorescence spectroscopy study of synthetic food colors].

According to the characteristic of synthetic food colors molecule and the relationship between fluorescence and molecular structure, and through analyzing, it has been concluded that synthetic food colors is fluorescent material. By using SP-2558 multifunctional spectral measuring system, the three-dimensional fluorescence spectra of ponceau 4R, amaranth, tartrazine, sunset yellow and brilliant blue were measured. The results show that ponceau 4R excited by light at the wavelength of 330-430 nm can generate a strong fluorescence at the 621 nm peak wavelength with its best excitation wavelength being 376 nm, amaranth excited by light at the wavelength of 300-440 nm can generate a strong fluorescence at the 643 nm peak wavelength with its best excitation wavelength being 370 nm, tartrazine excited by light at the wavelength of 280-380 nm can generate a strong fluorescence at the 565 nm peak wavelength with its best excitation wavelength being 315 nm, sunset yellow excited by light with wavelength of 310-410 nm can generate a strong fluorescence at the 592 nm peak wavelength with its best excitation wavelength being 348 nm, and brilliant blue excited by light at the wavelength of 320-390 nm can generate a strong fluorescence at the 456 nm peak wavelength with its best excitation wavelength being 350 nm. Moreover, the fluorescence spectra of the five kinds of synthetic food colors were discussed. These results can provide helps for testing of food colors and food safety.

[Fluorescence spectra of ponceau-4R].

The fluorescence spectra of ponceau 4R induced by 220-400 nm light were studied in the present paper. The result shows that ponceau 4R has four obvious fluorescence spectral peaks respectively located at 420, 530, 635 and 687 nm, each of these fluorescence spectral peaks has different best induced light, and the corresponding fluorescence spectra were listed. It was considered that this fluorescence comes from the transition n --> pi* of n electrons in the -OH and pi* --> pi of pi electrons in the naphthalene. The fluorescence spectral peaks at 420 nm come from the transition n --> pi* and the other three fluorescence spectral peaks come from pi* --> pi. But the intensity of the four fluorescence spectral peaks changes differently with the excited wavelength This paper attempted to give the expression of the four fluorescence spectral peaks based on the microcosmic mechanism. The reason for that ponceau 4R has complex fluorescence characteristic is that ponceau 4R not only has big and conjugate structure such as naphthalene and provides electron group -OH which can intensify its ability to emit fluorescence, but also absorbs electron group such as N=N which can depress its ability to emit fluorescence. Investigation on the fluorescence spectra and its characteristics will contribute to the study on the fluorescence spectra of other azo pigment and help find a new way for checking food safety.

[Study on ultraviolet fluorescence spectra of monomers of distilled spirits].

In the present paper, the authors measured the fluorescence spectra of water, alcohols and major microcrystalline substances of different distilled spirits and synthesized their three-dimensional fluorescence spectra. By comparing the fluorescence spectra of major monomers with those of many different kinds of distilled spirits, the authors found that ethanol and many other monomers can influence the fluorescence spectra of distilled spirits. Apart from ethanol, the major microcrystalline substances, such as alcohols, acids, aldehydes and esters influence the fluorescence spectra of distilled spirits respectively. In the meanwhile, their influences are different. The influences of different kinds of monomers differ from each other in the respects of wavelength and intensity. The order of the influences from low level to high level is: alcohols, aldehydes, acids and esters. But the same kind of monomers can bring about almost the same fluorescence spectra. So, the same kind of monomers influences the fluorescence spectra of distilled spirits similarly. To sum up, the authors come to a conclusion that apart from water, every kind of monomers can influence the fluorescence spectra of distilled spirits. And the order of the influences from low level to high level is: alcohols, aldehydes, acids and esters. In the meanwhile, they influence the fluorescence spectra in different spectral range respectively. The outcome of the study is very important for the further detailed research on the fluorescence spectra of distilled spirits in the future.