Selection of Anti‐gluten DNA Aptamers in a Deep Eutectic Solvent

Herein, we show the feasibility of using deep eutectic solvents as a faster way of selecting aptamers targeting poorly water‐soluble species. This unexplored concept is illustrated for gluten proteins. In this way, aptamer‐based gluten detection can be performed directly in the extraction media with improved detectability. We envision deep implications for applications not only in food safety control but also in biomedicine.     

A study of the photochemically induced electron-transfer reactions between pyridinedicarbonitriles and primary and secondary aliphatic amines

A study on the photochemically induced electron-transfer from primary and secondary aliphatic amines as donors to pyridinedicarbonitriles as the acceptor is reported. A comparison between the substitution positions and the spin density distributions, obtained via theoretical calculations using the 6-31+G basis set, shows some discrepancies, and forms the basis of a hypothesis on the mechanism of the reaction.     

Regioselective Oligomerization of 3-(Alkylsulfanyl)thiophenes with Ferric Chloride

The action of FeCl(3) on 3-(alkylsulfanyl)thiophenes (3-(alkylthio)thiophenes) leads to the one-step formation of regioregular alpha-conjugated oligothiophenes, from trimer to octamer, depending on the solvent used and on the length of the alkyl chain. The regiochemistry of these oligomers is characterized by one inner head-to-head linkage between adjacent rings and by a variable number of lateral head-to-tail junctions. The reaction of ferric chloride with the head-to-head and head-to-tail bis(methylsulfanyl)-2,2'-bithiophenes gives the corresponding tetramers, while the reaction with the tail-to-tail counterpart affords a high molecular weight insoluble material. With the aid of theoretical calculations, these results are interpreted on the basis of the joint effects of the orienting power of the substituents and of the stability of the radical cations formed during the oxidative process.     

A simple procedure for the chromatographic analysis of nanoliter samples

A simple method for the analysis of nanoliter droplets is proposed, which is profitable when larger samples cannot be collected as, for instance, in the case of several biological fluids and particularly in clinical chemistry. A glass capillary associated to a micromanipulator is used to collect submicroliter volumes which are partially transferred into transparent polymeric tubings with known internal diameters (120–178 μm), where the volumes sampled are measured by meniscus collimations with a collimator microscope at suitable magnification. Both ends of these tubings are preliminarily equipped with ferrules and fittings, so as to make them suitable for connection as the loop to a conventional high-pressure injection valve. The reliability of this procedure has been tested for the analysis of Na⁺, K⁺ and Ca²⁺ present in minute synthetic standard samples (10–200 nL) by a conventional ion-chromatographic instrumentation. Relative standard deviations in peak area measurements (5–6%) are discussed in terms of the whole approximation affecting volume measurements, which depends on both the inconstancy of the inner diameter of the polymeric tubings employed and the uncertainty characterizing meniscus collimations. The proposed procedure can be easily extended to the determination of any organic or inorganic species present in very small samples, provided that their detection can be achieved by any chromatographic approach or, more generally, by flow injection analysis.     

ICP-MS determination of toxic-metal release from pumping systems for food processing

The release of heavy metals from uncovered and nickel-covered brass pumps has been evaluated by ICP-MS analysis in both simple ultrapure water and 3% acetic acid solution (mimic of neutral and acid edible liquids, respectively), following a procedure similar to that recommended by the National Sanitation Foundation (NSF) International, Test Procedure P203. The results found highlight that the main release regards zinc, copper and lead, i.e. the three major metals present in brass alloys. The first contact of brass surfaces with the extraction solvent leads to an extensive Pb release which is comparable with that observed for Cu and Zn. Subsequent washings reduce markedly the Pb release, thus rising in evidence a progressive surface passivation. In particular, the Pb release found after four repeated washings turns out to approach the limit set by both Italian and USA governments for liquids used for food purposes when determined in neutral media, while it remains quite higher when evaluated in acid media. Release analyses conducted on nickel-covered brass pumps point out that the Niploy nickel coating process is very effective for brass surface protection, in that the Pb release is reduced of about three orders of magnitude, but a Ni release exceeding the relevant permitted level is in this case observed.     

Cyclizations of N-stannylaminyl radicals onto nitriles

[reaction: see text] Stannylaminyl radicals derived from radical reactions of Bu(3)SnH with azidoalkylmalononitriles exhibit highly efficient 5- and 6-exo cyclization onto either nitrile group to give aminoiminyl radicals that in turn are reduced to amidines or undergo successive 5-exo cyclization onto an internal alkene.     

Different binding thermodynamics of Ni2+, Cu2+, and Zn2+ to bacitracin A1 determined by capillary electrophoresis

Thermodynamics of the binding of Ni(2+), Cu(2+) and Zn(2+) to bacitracin A(1) was studied by capillary electrophoresis measuring the peptide effective mobility at different pH in the presence of increasing concentration of the three ligands. The affinity follows the order Ni(2+) > Cu(2+) > Zn(2+), with association constant values of (2.3 +/- 0.1)x10(4), (4.9 +/- 0.2)x10(3), and (1.5 +/- 0.1)x10(3) M(-1), respectively. The only model able to rationalize mobility data implies that metal ion binds to the P(0) peptide form. Moreover, mobility values indicated a change of bacitracin A(1) acidic properties on Ni(2+) and Cu(2+) binding, with a shift of the pK(a) of N-terminal Ile-1 from 7.6 to about 5 and of the pK(a) of the delta-amino group of D-Orn-7 from 9.7 to about 7. Even though on Zn(2+) binding a shift of the N-terminal Ile-1 pK(a) was observed, restrictions in the pH range suitable for investigation, due to precipitation phenomena, did not allow establish if the shift of D-Orn-7 lateral chain pK(a) also occurred. Nonetheless, if present, the shift should be limited to the 7.8-9.7 range. Mobility data indicated that the Stokes radius of the complexes is ca. 3 A lower than that of the free peptide. The present results indicate that metal-ion binding to bacitracin A(1) is more complex than previously assumed.     

Chromatographische Trennung der Isomere Pyridyl-3- und -4-acryls?ure

Zusammenfassung Die Isomere Pyridyl-3- und -4-acrylsäure können papierchromatographisch mit dem Lösungsmittelsystem Butanol-Essigsäure-Wasser (501436) nach der auf- oder absteigenden Technik gut voneinander getrennt werden. Der Nachweis erfolgt mit Joddampf. Noch 10g können erfaßt werden.

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Summary The isomers pyridyl-3- and -4-acrylic acid can be well separated by paper chromatography using the ascending or descending technique and the solvent system butanol-acetic acid-water (501436). The spots are developed by iodine vapours. 10 g of each isomer can be detected.