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Fatty acid (FA) profiling provides phenotypic information and is increasingly used in a broad range of biological and biomedical studies. Quantitation of unsaturated FAs with confident carbon-carbon double bond (C=C) location assignment is both sample and time consuming using traditional gas chromatography mass spectrometry analysis. In this study we developed a rapid, sensitive, and quantitative method for profiling unsaturated FAs without using chromatographic separations. This method was based on a combination of in-solution photochemical tagging of a C=C in FAs and a subsequent gas-phase de-tagging via tandem (neutral loss scan) mass spectrometry. It enabled quantitation of unsaturated FAs from various biological samples (blood, plasma, and cell lines). More importantly, quantitative information of FA C=C location isomers, which was traditionally overlooked, could now be obtained and applied to studying FA changes between normal and cancerous human prostate cells.

Unsaturated fatty acids (FAs) serve as nutrients, energy sources, and signaling molecules for organisms, which are the major components for a large variety of lipids. However, structural characterization and quantitation of unsaturated FAs by mass spectrometry remain an analytical challenge. Here, we report the coupling of epoxidation reaction of the C═C in unsaturated FAs and tandem mass spectrometry (MS) for rapid and accurate identification and quantitation of C═C isomers of FAs in a shotgun lipidomics approach. Epoxidation of the C═C leads to the production of an epoxide which, upon collision induced dissociation (CID), produces abundant diagnostic ions indicative of the C═C location. The total intensity of the same set of diagnostic ions for one specific FA C═C isomer was also used for its relative and absolute quantitation. The simple experimental setup, rapid reaction kinetics (<2 min), high reaction yield (>90% for monounsaturated FAs), and easy-to-interpret tandem MS spectra enable a promising methodology particularly for the analysis of unsaturated FAs in complex biological samples such as human plasma and animal tissues.

Comprehensive analysis of single-cell metabolites is critical since differences in cellular chemical compositions give rise to specialized biological functions. Herein, we propose a label-free mass cytometry by coupling flow cytometry to ESI-MS (named CyESI-MS) for high-coverage and high-throughput detection of cellular metabolites. Cells in suspension were isolated, online extracted by sheath fluid, and lysed during gas-assisted electrospray, followed by real-time MS analysis. Hundreds of metabolites, including nucleotides, amino acids, peptides, carbohydrates, fatty acyls, glycerolipids, glycerophospholipids, and sphingolipids, were detected and identified from one single cell. Discrimination of four types of cancer cell lines and even three subtypes of breast cancer cells was readily achieved using their distinct metabolic profiles. Furthermore, we screened out 102 characteristic ions from 615 detected peak signals for distinguishing breast cancer cell subtypes and identified 40 characteristic molecules which exhibited significant differences among these subtypes and would be potential metabolic markers for clinical diagnosis. CyESI-MS is expected to be a new-generation mass cytometry for studying cell heterogeneity on the metabolic level.

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Being motivated by the issue of waste electrical and electronic equipment (WEEE) collection, we consider a contract design problem for a manufacturer with entrusting the collection of WEEE to a retailer. However, the manufacturer has asymmetric information on the collection effort level of the retailer. This paper designs an information screening contract for the manufacturer to obtain the information of collection effort level, and the optimal decision-making with several properties of contract parameters are derived. The results indicate that the manufacturer would offer lower wholesale price and higher buy-back price for the H-type retailer while charge more franchise fee to the H-type retailer. Considering the government intervention, reward-penalty mechanism (RPM) is developed to stimulate the asymmetric information closedloop supply chain (CLSC). We also analyze the impacts of RPM by comparing the cases whether or not RPM is implemented. The comparison results show that the RPM can lower the wholesale price and retail price meanwhile raise buy-back price and collection quantity. Finally, several numerical studies are conducted for more managerial insights.

Poly(vinylidene fluoride) (PVDF) chains with the same expanded state were obtained by dissolving PVDF resin in good solvent. Then, the crystallization of PVDF chains from mixed solvents composed of its good solvent and nonsolvent was investigated. N,N-dimethylformamide (DMF) and ethanol were used as good solvent and nonsolvent of PVDF, respectively. The crystalline phases of PVDF were characterized by Fourier transform infrared (FTIR) spectroscopy and wide angle X-ray diffraction (WAXD). For the crystallization of PVDF chains from mixed solvents, low ethanol content favored the formation of b phase, while high ethanol content resulted predominantly in the a phase. Different crystallization morphology was observed from the scanning electron microscopy (SEM) images. The obvious spherulite morphol-ogy disappeared with the increase in ethanol content in mixed solvent. According to thermal analyses, the crystallized PVDF from mixed solvents with high ethanol content had lower onset melting temperatures than that from low ethanol content. Smaller lamellar thickness calculated from WAXD data reasoned the low onset melting temperatures. The above results indicated that the crystallization of PVDF chains from mixed solvent was a ''controlled'' process by ethanol content. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 575-581, 2010

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