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61.
Paola Scano Antonella Rosa Emanuela Locci Giorgia Manzo M. Assunta Dessì 《Magnetic resonance in chemistry : MRC》2012,50(6):436-442
1H NMR spectroscopy was employed to study the modifications over time of the water‐soluble low molecular weight metabolites extracted from samples of salted and dried mullet (Mugil cephalus) roes (mullet bottarga) stored at different conditions. Samples of grated mullet bottarga were stored for 7 months at ?20 °C, at 3 °C, and at room temperature in the presence and in the absence of light and then timely extracted and analyzed by NMR. Principal component multivariate data analysis applied to the spectral data indicated that samples stored at ?20 °C maintained similar features over time whereas, along PC1, samples stored at room temperature in the presence and in the absence of light showed, over time, marked metabolite modifications. The comparative analysis of the integrated areas of the selected regions of the 1H NMR spectra indicated that the major compositional changes due to storage conditions were (i) the increase of the derivatives of the breakdown of phosphatidylcholine (choline, phosphorylcholine, and glycerol), (ii) the breakdown of nucleosides, (iii) the decrease of methionine, tryptophan, and tyrosine, and (iv) the cyclization of creatine. These changes were observed at different storage conditions, with more pronounced trends in the samples stored at room temperature. The role of metabolites in food aging is discussed. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
62.
The occurrence of mineral oil in food is known since the early 1990s, and it was discovered by chance in one of the first applications using the hyphenated LC–GC system. Since then, the relationship between hyphenated techniques and mineral oil analysis has been tightly interrelated and successful. This review aims to show and explain how this mutual interaction has driven the development of the hyphenated techniques on one side and has supported the increase of knowledge on the other, supporting the complex task of mineral oil determination in food. The paper presents the background of the mineral oil problem in food (a brief history of its finding, toxicology, and occurrence), moving then toward the analytical determination. The development of different hyphenated techniques in relation to mineral oil determination is discussed, focusing mainly on 2D techniques, such as LC–GC. The necessity of additional dimensions, such as LC–LC–GC and comprehensive approaches, such as GC × GC and LC × GC, is also discussed. Finally, the role of the hyphenation with MS is presented. 相似文献
63.
The urgency of integrating renewable energy sources in the power grid has pushed the development of aqueous metal-ion batteries because of their low cost, nontoxicity, high safety, and environmentally friendliness. Among the variety of aqueous metal-ion batteries that are currently under development, aqueous Zn-ion batteries (A-ZIBs) have recently gained a great attention because of their high specific energy and high reversibility in aqueous solutions, together with the low cost and high abundancy of the zinc. In this article, the authors intend to present an overview of the Prussian blue analogue materials, which are among the most promising materials for positive electrodes in A-ZIBs because of their easier synthesis route, reversible ion-insertion, high safety, and low toxicity, highlighting their strength points and open challenges. 相似文献
64.
Kristian J. Chambers Patthadon Sanghong Daniel Carter Martos Dr. Giorgia Casoni Dr. Rory C. Mykura Dr. Durga Prasad Hari Dr. Adam Noble Prof. Varinder K. Aggarwal 《Angewandte Chemie (International ed. in English)》2023,62(50):e202312054
Enones are widely utilized linchpin functional groups in chemical synthesis and molecular biology. We herein report the direct conversion of boronic esters into enones using commercially available methoxyallene as a three-carbon building block. Following boronate complex formation by reaction of the boronic ester with lithiated-methoxyallene, protonation triggers a stereospecific 1,2-migration before oxidation generates the enone. The protocol shows broad substrate scope and complete enantiospecificity is observed with chiral migrating groups. In addition, various electrophiles could be used to induce 1,2-migration and give a much broader range of α-functionalized enones. Finally, the methodology was applied to a 14-step synthesis of the enone-containing polyketide 10-deoxymethynolide. 相似文献
65.
Giorgia Callegaro M’hamed Gaïgi Simone Scotti Carlo Sgarra 《Mathematics and Financial Economics》2017,11(3):299-322
In this paper we introduce a jump-diffusion model of shot-noise type for stock prices, taking into account over and under-reaction of the market to incoming news. We work in a partial information setting, by supposing that standard investors do not have access to the market direction, the drift, (modeled via a random variable) after a jump. We focus on the expected (logarithmic) utility maximization problem by providing the optimal investment strategy in explicit form, both under full (i.e., from the insider point of view, aware of the right kind of market reaction at any time) and under partial information (i.e., from the standard investor viewpoint, who needs to infer the kind of market reaction from data). We test our results on market data relative to Enron and Ahold. The three main contributions of this paper are: the introduction of a new market model dealing with over and under-reaction to news, the explicit computation of the optimal filter dynamics using an original approach combining enlargement of filtrations with Innovation Theory and the application of the optimal portfolio allocation rule to market data. 相似文献
66.
Sciutto G Dolci LS Buragina A Prati S Guardigli M Mazzeo R Roda A 《Analytical and bioanalytical chemistry》2011,399(9):2889-2897
The identification and localization of organic components in the complex stratigraphy of paintings play a crucial role in
studies of painting techniques and authentication, restoration, and conservation of artworks. Much scientific effort has been
expended for the development of analytical approaches suitable for the investigation and characterization of organic substances,
allowing high sensitivity, specificity, and spatial resolution. Proteins (e.g., ovalbumin, casein, and collagen from different
animal sources) are one of the classes of organic substances most widely used as painting materials. The analytical techniques
commonly used for their analysis (micro Fourier transform infrared spectroscopy, chromatographic techniques, and proteomic
approaches) have limits related to the lack of specificity or to the absence of information concerning the stratigraphic localization
of the detected proteins. Immunological techniques are a promising alternative approach for the characterization of proteins
in artworks. Thanks to the high specificity of antigen–antibody reactions, these techniques are widely used for the analysis
of proteins in bioanalytical and clinical chemistry and recently they have been successfully applied in the field of science
for conservation of cultural heritage. The present research aimed to develop an ultrasensitive chemiluminescent immunochemical
procedure for the simultaneous localization of ovalbumin and bovine casein (two common proteins found in binding media or
varnishes of artistic and archaeological samples) in resin-embedded painting micro cross-sections. The possibility of performing
the simultaneous identification of different proteins in painting cross-sections is of particular relevance in the field of
cultural heritage because samples are often small and available in a limited number; therefore, the maximum amount of information
must be obtained from each of them. 相似文献
67.
De Mori G Fu Z Viola E Cai X Ercolani C Donzello MP Kadish KM 《Inorganic chemistry》2011,50(17):8225-8237
A series of pyrazinoporphyrazine macrocycles carrying externally appended 2-thienyl rings, represented as [Th(8)TPyzPzM], where Th(8)TPyzPz = tetrakis-2,3-[5,6-di(2-thienyl)pyrazino]porphyrazinato anion and M = Mg(II)(H(2)O), Zn(II), Co(II), Cu(II), or 2H(1), were prepared and isolated as solid air-stable hydrated species. All of the compounds, completely insoluble in water, were characterized by their UV-visible spectra and electrochemical behavior in solutions of dimethylformamide (DMF), dimethyl sulfoxide, and pyridine. Molecular aggregation occurs at concentrations of ca. 10(-4) M, but monomers are formed in more dilute solutions of 10(-5) M or less. The examined octathienyl compounds [Th(8)TPyzPzM] behave as electron-deficient macrocycles, and UV-visible spectral measurements provide useful information about how the peripheral thienyl rings influence the electronic distribution over the entire macrocyclic framework. Cyclic voltammetric and spectroelectrochemical data confirm the easier reducibility of the compounds as compared to the related phthalocyanine analogues, and the overall redox behavior and thermodynamic potentials for the four stepwise one-electron reductions of the compounds are similar to those of the earlier examined octapyridinated analogues [Py(8)TPyzPzM]. Quantum yields (Φ(Δ)) for the generation of singlet oxygen, (1)O(2), the cytotoxic agent active in photodynamic therapy (PDT), and fluorescence quantum yields (Φ(F)) were measured for the Zn(II) and Mg(II) complexes, [Th(8)TPyzPzZn] and [Th(8)TPyzPzMg(H(2)O)], and the data were compared to those of corresponding octapyridino macrocycles [Py(8)TPyzPzZn] and [Py(8)TPyzPzMg(H(2)O)] and their related octacations [(2-Mepy)(8)TPyzPzZn](8+) and [(2-Mepy)(8)TPyzPzMg(H(2)O)](8+). These measurements were carried out in DMF and in DMF preacidified with HCl (ca. 10(-4) M). All of the examined Zn(II) compounds behave as excellent photosensitizers (Φ(Δ) = 0.4-0.6) both in DMF and DMF/HCl solutions, whereas noticeable fluorescence activity (Φ(F) = 0.36-0.43) in DMF/HCl solutions is shown by the Mg(II) derivatives; these data might provide perspectives for applications in PDT (Zn(II)) and imaging response and diagnosis (Mg(II)). 相似文献
68.
Piccialli V Zaccaria S Centore R Tuzi A Borbone N Oliviero G 《Molecules (Basel, Switzerland)》2011,16(7):5362-5373
A novel bis-iodurated polyether compound, based on an unprecedented tetra-THF backbone, has been isolated as a trace by-product of the oxidation of squalene with the catalytic system RuO?(cat.)/NaIO?. The double erythro configuration of the central portion of the molecule furnishes the first indirect support of the previously postulated pathway operating in the oxidative pentacyclization of the isoprenoid substrate. A bidirectional double oxidative bis-cyclization is invoked to explain the formation of this compound. The isolated substance was successfully subjected to a double rearrangement-ring expansion to give a novel bis-THF-bis-THP compound. 相似文献
69.
Greco G Panzella L Gentile G Errico ME Carfagna C Napolitano A d'Ischia M 《Chemical communications (Cambridge, England)》2011,47(37):10308-10310
An oxygen-dependent biomimetic system for DOPA, dopamine and norepinephrine polymerization exploiting the redox properties of a 5-S-cysteinylDOPA (CD)-melanin polymer is disclosed. Kinetic, chemical and scanning electron microscopy (SEM) evidence indicates conversion of DOPA into a black insoluble polymer encapsulating the active CD-melanin core. 相似文献
70.
The photostability of quercetin in alcoholic solutions was studied. Both UVA and UVB light induced degradation of quercetin, yielding a single product 1 deriving from oxidation and addition of an alcohol molecule to the 2,3 double bond. The same mechanism operated when quercetin was dissolved in alkaline solutions, and again a product 2 due to oxidation and addition of water was characterized. Comparison with quercetin analogs confirmed that, despite the presence of five hydroxy groups in quercetin, those in positions 3, 3', and 4' are mainly involved in the antioxidant activity of the compound , as well as in its photolability. 相似文献