Direct molecule-specific glucose detection by Raman spectroscopy based on photonic crystal fiber

This paper reports the first step toward the development of a glucose biosensor based on Raman spectroscopy and a photonic crystal fiber (PCF) probe. Historically, it has been very challenging to detect glucose directly by Raman spectroscopy due to its inherently small Raman scattering cross-section. In this work, we report the first quantitative glucose Raman detection in the physiological concentration range (0–25 mM) with a low laser power (2 mW), a short integration time (30 s), and an extremely small sampling volume (∼50 nL) using the highly sensitive liquid-filled PCF probe. As a proof of concept, we also demonstrate the molecular specificity of this technique in the presence of a competing sugar, such as fructose. High sensitivity, flexibility, reproducibility, low cost, small sampling volume, and in situ remote sensing capability make PCF a very powerful platform for potential glucose detection based on Raman spectroscopy.     

Circularly‐Polarized Electrochemiluminescence from a Chiral Bispyrene Organic Macrocycle

The first observation of circular polarization of electrochemiluminescence (ECL) from a purely organic derivative is reported. A bispyrene scaffold mounted on a constrained polyether macrocycle displaying intense excimer fluorescence and highly circularly‐polarized (CP) photoluminescence has been selected for this purpose. The compound displays an ECL dissymmetry factor of about |8×10^?3|, which is in good agreement with the corresponding photoluminescence value. This observation is the first step towards the molecular engineering of tailored dyes that can act as both ECL and CP‐ECL reporters for (bio)analysis by bringing a new level of information when dealing with chiral environments. Additionally, it provides an extra dimension to the ECL phenomenon and opens the way to chiral detection and discrimination.     

Results of the 16th proficiency test on the determination of pesticide residues in olive oil

Accreditation and Quality Assurance - The Italian National Reference Laboratory (NRL) for pesticide residues yearly organizes proficiency tests (PTs) on olive oil in cooperation with the...     

Integration of grating couplers with a compact photonic crystal demultiplexer on an InP membrane

We demonstrate the integration of a 30% efficient grating coupler with a compact photonic crystal wavelength demultiplexer (DeMUX). The DeMUX has seven output channels that are spaced 10 nm apart and is aimed at coarse WDM applications. The integrated devices are realized on a high-index-contrast InP membrane using a simple benzocyclobutene wafer bonding technique. Cross talks of -10 to -12 dB for four channels 20 nm apart are obtained without optimization.     

An exploration of social identity: The structure of the BBC news‐sharing community on Twitter

Online social media influence the flow of news and other information, potentially altering collective social action while generating a large volume of data useful to researchers. Mapping these networks may make it possible to predict the course of social and political movements, technology adoption, and economic behavior. Here, we map the network formed by Twitter users sharing British Broadcasting Corporation (BBC) articles. The global audience of the BBC is primarily organized by language with the largest linguistic groups receiving news in English, Spanish, Russian, and Arabic. Members of the network primarily “follow” members sharing articles in the same language, and these audiences are primarily located in geographical regions where the languages are native. The one exception to this rule is a cluster interested in Middle East news which includes both Arabic and English speakers. We further analyze English‐speaking users, which differentiate themselves into four clusters: one interested in sports, two interested in United Kingdom (UK) news—with word usage suggesting this reflects political polarization into Conservative and Labour party leanings—and a fourth group that is the English speaking part of the group interested in Middle East news. Unlike the previously studied New York Times news sharing network the largest scale structure of the BBC network does not include a densely connected group of globally interested and globally distributed users. The political polarization is similar to what was found for liberal and conservative groups in the New York Times study. The observation of a primary organization of the BBC audience around languages is consistent with the BBC's unique role in history as an alternative source of local news in regions outside the UK where high quality uncensored news was not available. © 2014 Wiley Periodicals, Inc. Complexity 19: 55–63, 2014     

Evaluation of a fibre optic device in solution equilibria studies. Application to 3-hydroxybenzoic acid ionization

The use of a fibre optic device for spectrophotometric measurements in solution equilibria studies is presented. In particular the precision obtainable with such equipment is evaluated as a function of different experimental conditions, such as path length, averaging time and stirring of the solution. Analysis of 3-hydroxybenzoic acid ionization is presented to assess the results obtained in the study of an equilibrium system.     

Macrotricyclic Steroid Receptors by Pd°-Catalyzed Cross-Coupling Reactions: Dissolution of cholesterol in aqueous solution and investigations of the principles governing selective molecular recognition of steroidal substrates

Three double-decker cyclophane receptors, (±)- 2 , (±)- 3 , and (±)- 4 with 11–13-Å deep hydrophobic cavities were prepared and their steroid-binding properties investigated in aqueous and methanolic solutions. Pd°-Catalyzed cross-coupling reactions were key steps in the construction of these novel macrotricyclic structures. In the synthesis of D₂-symmetrical (±)- 2 , the double-decker precursor (±)- 7 was obtained in 14% yield by fourfold Stille coupling of equimolar amounts of bis(tributylstannyl)acetylene with dibromocyclophane 5 (Scheme 1). For the preparation of the macrotricyclic precursor (±)- 15 of D₂-symmetrical (±)- 3 , diiodocylophane 12 was dialkynylated with Me₃SiC?CH to give 13 using the Sonogashira cross-coupling reaction; subsequent alkyne deprotection yielded the diethynylated cyclophane 14 , which was transformed in 42% yield into (±)- 15 by Glaser-Hay macrocyclization (Scheme 2). The synthesis of the C₂-symmetrical conical receptor (±)- 4 was achieved via the macrotricyclic precursor (±)- 25 , which was prepared in 20% yield by the Hiyama cross-coupling reaction between the diiodo[6.1.6.1]paracyclophane 19 and the larger, dialkynylated cyclophane 17 (Scheme 4). Solid cholesterol was efficiently dissolved in water through complexation by (±)- 2 and (±)- 3 , and the association constants of the formed 1:1 inclusion complexes were determined by solid-liquid extraction as K_a = 1.1 × 10⁶ and 1.5 × 10⁵ l mol^?1, respectively (295 K) (Table 1). The steroid-binding properties of the three receptors were analyzed in detail by ¹H-NMR binding titrations in CD₃OD. Observed steroid-binding selectivities between the two structurally closely related cylindrical receptors (±)- 2 and (±)- 3 (Table 2) were explained by differences in cavity width and depth, which were revealed by computer modeling (Fig. 4). Receptor (±)- 2 , with two ethynediyl tethers linking the two cyclophanes, possesses a shallower cavity and, therefore, is specific for flatter steroids with a C(5)?C(6) bond, such as cholesterol. In contrast, receptor (±)- 3 , constructed with longer buta-1,3-diynediyl linkers, has a deeper and wider hydrophobic cavity and prefers fully saturated steroids with an aliphatic side chain, such as 5α-cholestane (Fig. 7). In the 1:1 inclusion complexes formed by the conical receptor (±)- 4 (Table 3), testosterone or progesterone penetrate the binding site from the wider cavity side, and their flat A ring becomes incorporated into the narrower [6.1.6.1]paracyclophane moiety. In contrast, cholesterol penetrates (±)- 4 with its hydrophobic side chain from the wider rim of the binding side. This way, the side chain is included into the narrower cavity section shaped by the smaller [6.1.6.1]paracyclophane, While the A ring protrudes with the OH group at C(3) into the solvent on the wider cavity side (Fig. 8). The molecular-recognition studies with the synthetic receptors (±)- 2 , (±)- 3 , and (±)- 4 complement the X-ray investigations on biological steroid complexes in enhancing the understanding of the principles governing selective molecular recognition of steroids.     

Synthese einiger 8-substituierter 2-Methyl-1,2,3,4-tetrahydroisochinoline

Synthesis of Some 8-Substituted 2-Methyl-1,2,3,4-tetrahydroisoquinolines A general route to 8-substituted tetrahydroisoquinolines is exemplified by the preparation of the 2-methyl-1,2,3,4-tetrahydroisoquinolin-8-ol ( 11 ), the -8-carbaldehyde oxime ( 12 ) and the -8-carbonitrile ( 13 ). It involves the conversion of isoquinoline ( 1 ) by partially modified Steps 1, 2, 3, and 5 (see the Scheme) into the 5-bromo-8-nitro derivative 5 , reduction of the latter to the 8-amino derivative 8 and replacement of the NH₂-group with an appropriate substituent by a Sandmeyer-like reaction. The selective reductions of the N-containing ring in 6 (Steps 5, 6, and 8) and of the NO₂-group in 5 (Steps 4 and 7) were also studied.