Metabonomics studies of intact hepatic and renal cortical tissues from diabetic db/db mice using high-resolution magic-angle spinning 1H NMR spectroscopy

A metabonomics approach based on high-resolution magic-angle spinning (HRMAS) ¹H NMR spectroscopy was applied to investigate the metabolite composition in intact hepatic tissues and renal cortical tissues from db/db mice of 8 weeks old, an animal model of type 2 diabetes mellitus. Compared to the control group, the hepatic tissues of diabetic mice have elevated levels of triglyceride and bile acid and declined levels of trimethylamine-N-oxide, phosphocholine, glycerophosphocholine, and choline. The biochemical changes are less obvious in renal cortical tissues of diabetic mice. The WET_CPMG pulse sequence was selected for our metabonomics study after the quality and reproducibility of the spectra obtained from the NOEPR, NOEPR_CPMG, and WET_CPMG pulse sequences were analyzed together with principal component analysis. The influence of line-broadening factor of exponential window function for spectral manipulation on class separation was paid attention to for the first time, and an optimal value was obtained under our experimental conditions. These studies show the efficiency of HRMAS ¹H NMR spectroscopy for tissue metabonomics study in combination with multivariate statistical analysis, which may help to explore the etiological factor of diabetes mellitus from a new perspective.

Noninvasive depth profiling of walls by portable nuclear magnetic resonance

A compact and mobile single-sided ¹H NMR sensor, the NMR-MOUSE®, has been employed in the nondestructive characterization of the layer structure of historic walls and wall paintings. Following laboratory tests on a model hidden fresco, paint and mortar layers were studied at Villa Palagione and the Seminario Vescovile di Sant’ Andrea in Volterra, Italy. Different paint and mortar layers were identified, and further characterized by portable X-ray fluorescence spectroscopy where accessible. In the detached and restored fresco “La Madonna della Carcere” from the Fortezza Medicea in Volterra, paint and mortar layers were discriminated and differences in the moisture content of the adhesive that fixes the detached wall painting to its support were found in both restored and original sections. These investigations encourage the use of the portable and single-sided NMR technology for nondestructive studies of the layer structure and conservation state of historic walls.

Detection of catecholamines in single specimens of groundwater amphipods

Catecholamines play essential roles in several physiological processes in vertebrates as well as in invertebrates. While several studies have shown the presence of these substances in surface water invertebrates, their occurrence in groundwater fauna is unproven. In the present study, the presence of different catecholamines (i.e., noradrenaline, adrenaline, and dopamine) in individual specimens of groundwater amphipods of the genus Niphargus (mostly Niphargus inopinatus) was investigated via two independent analytical methods: HPLC/EcD and UPLC/TOF-MS. Mean values for catecholamine levels were 533 pg mg^?1 fresh weight for noradrenaline, 314 pg mg^?1 for adrenaline, and 16.4 ng mg^?1 for dopamine. The optimized protocol allowed the detection of CAs in single organisms of less than 1 mg fresh weight. Catecholamine concentration patterns in groundwater invertebrates are briefly discussed here with respect to their evolutionary adaptation to an environmentally stable, energy-poor habitat.

Poly(bismethylene hydroquinone) (PBHQ). I. Synthesis and characterization

Poly(bismethylene hydroquinone) (PBHQ) has been synthesized. Fourier transform infrared, ¹³C solid-state CP/MAS NMR and elemental analysis provide strong evidence of two methylene bridges per hydroquinone molecule. The polymer was (1) air oxidized using ammonia and (2) chemically oxidized using bromine/KOH. The initial structure and oxidation process was studied by comparison of the unoxidized and oxidized polymers using Fourier transform infrared, elemental analysis, and ¹³C solid-state CP/MAS NMR.     

Oxygen consumption by conserved archaeological wood

Rates of oxygen consumption have been measured over extended time periods for 29 whole samples of conserved, archaeological wood and four samples of fresh, unconserved wood, at 50 % relative humidity and room temperature. Samples from the Swedish Warship Vasa and the Danish Skuldelev Viking ships are included. Most rates were close to 1 μg O₂ (g wood)^?1 day^?1 and the process persisted for several years at least. Consumption of oxygen is related to change in chemical composition, which is, in turn, related to degradation. It is thus demonstrated that despite conservation, waterlogged archaeological wood continues to degrade in a museum climate.

Non-invasive NMR stratigraphy of a multi-layered artefact: an ancient detached mural painting

NMR stratigraphy was used to investigate in situ, non-destructively and non-invasively, the stratigraphy of hydrogen-rich layers of an ancient Nubian detached mural painting. Because of the detachment procedure, a complex multi-layered artefact was obtained, where, besides layers of the original mural painting, also the materials used during the procedure all became constitutive parts of the artefact. NMR measurements in situ enabled monitoring of the state of conservation of the artefact and planning of minimum representative sampling to validate results obtained in situ by solid-state NMR analysis of the samples. This analysis enabled chemical characterization of all organic materials. Use of reference compounds and prepared specimens assisted data interpretation.

Fluorine Bonding Enhances the Energetics of Protein-Lipid Binding in the Gas Phase

This paper reports on the first experimental study of the energies of noncovalent fluorine bonding in a protein-ligand complex in the absence of solvent. Arrhenius parameters were measured for the dissociation of gaseous deprotonated ions of complexes of bovine β-lactoglobulin (Lg), a model lipid-binding protein, and four fluorinated analogs of stearic acid (SA), which contained (X =) 13, 15, 17, or 21 fluorine atoms. In all cases, the activation energies (E_a) measured for the loss of neutral XF-SA from the (Lg + XF-SA)^7– ions are larger than for SA. From the kinetic data, the average contribution of each?>?CF₂ group to E_a was found to be ~1.1 kcal mol^–1, which is larger than the ~0.8 kcal mol^–1 value reported for?>?CH₂ groups. Based on these results, it is proposed that fluorocarbon–protein interactions are inherently stronger (enthalpically) than the corresponding hydrocarbon interactions.

A sensitive immunosorbent bio-barcode assay based on real-time immuno-PCR for detecting 3,4,3',4'-tetrachlorobiphenyl

A functionalized gold-nanoparticle bio-barcode assay, based on real-time immuno-PCR (IPCR), was designed for the determination of 3,4,3',4'-tetrachlorobiphenyl (PCB77). 15 nm gold nanoparticles were synthesized, and modified with thiol-capped DNA and goat anti-rabbit IgG. The nanoparticle probes were used to replace antibody–DNA conjugate in the IPCR, and were fixed on the PCR tube wall via the immune reaction. Real-time PCR was performed to quantify the DNA signal directly. Under optimized conditions, the new method was used to detect PCB77 with a linearity range from 5 pg L^?1 to 10 ng L^?1, and the limit of detection (LOD) was 1.72 pg L^?1. Real samples of Larimichthys polyactis, collected from the East China Sea, were analyzed. Recovery was from 82 % to 112 %, and the coefficient of variation (CV) was acceptable. The results were compared with GC–ECD, revealing that the method would be acceptable for providing rapid, semi-quantitative, and reliable test results for making environmental decisions.

Comparison of fullerene and large argon clusters for the molecular depth profiling of amino acid multilayers

A major challenge regarding the characterization of multilayer films is to perform high-resolution molecular depth profiling of, in particular, organic materials. This experimental work compares the performance of C₆₀ ⁺ and Ar₁₇₀₀ ⁺ for the depth profiling of model multilayer organic films. In particular, the conditions under which the original interface widths (depth resolution) were preserved were investigated as a function of the sputtering energy. The multilayer samples consisted of three thin δ-layers (~8 nm) of the amino acid tyrosine embedded between four thicker layers (~93 nm) of the amino acid phenylalanine, all evaporated on to a silicon substrate under high vacuum. When C₆₀ ⁺ was used for sputtering, the interface quality degraded with depth through an increase of the apparent width and a decay of the signal intensity. Due to the continuous sputtering yield decline with increasing the C₆₀ ⁺ dose, the second and third δ-layers were shifted with respect to the first one; this deterioration was more pronounced at 10 keV, when the third δ-layer, and a fortiori the silicon substrate, could not be reached even after prolonged sputtering. When large argon clusters, Ar₁₇₀₀ ⁺, were used for sputtering, a stable molecular signal and constant sputtering yield were achieved throughout the erosion process. The depth resolution parameters calculated for all δ-layers were very similar irrespective of the impact energy. The experimental interface widths of approximately 10 nm were barely larger than the theoretical thickness of 8 nm for the evaporated δ-layers.

Colorimetric and visual determination of melamine by exploiting the conformational change of hemin G-quadruplex-DNAzyme

We report on the detection of trace quantities of melamine (MA) by a colorimetric method that exploits the conformational change of hemin G-quadruplex-DNAzyme. The addition of MA to hemin G-quadruplex-DNAzyme structure containing thymine bases causes the thymine in the DNAzyme to interact with MA via a stable triple H-bond and leads to a conformational change. This, in turn, affects the peroxidase-like activity of hemin which is determined colorimetrically at 450 nm by adding 3,3’,5,5’-tetramethylbenzidine and hydrogen peroxide. The method was applied to the colorimetric determination of MA over a wide range of concentrations (0.2 to 24 μM) with a detection limit of 80 nM. The effect also can be detected with bare eyes. The method was successfully applied to the determination of MA in spiked milk powder.

Green biosynthesis of silver nanoparticles and nanomolar detection of p-nitrophenol

Green biosynthesis of nanoparticles and their applications in sensor field is of great interest to the researchers. We report herein a simple green approach for the synthesis of silver nanoparticles (Ag-NPs) using Acacia nilotica Willd twig bark and its application for the detection of 4-nitro phenol (4-NP). The synthesized Ag-NPs were characterized by Transmission electron microscopy, X-ray diffraction and elemental analysis. The size of synthesized Ag-NPs was in the range of 10–50 nm. The Ag-NPs modified electrode shows a high sensitivity and selectivity towards the sensing of 4-NP. The fabricated modified electrode shows a low detection limit of 15 nM on the wider linear response range from 100 nM to 350 μM with the sensitivity of 2.58?±?0.05 μAμM^?1 cm^?2. In addition, the fabricated sensor shows good repeatability and reproducibility.

Determination of organophosphate pesticides using an acetylcholinesterase-based biosensor based on a boron-doped diamond electrode modified with gold nanoparticles and carbon spheres

We report on a biosensor for organophosphate pesticides (OPs) by exploiting their inhibitory effect on the activity of acetylcholinesterase (AChE). A boron-doped diamond (BDD) electrode was modified with a nanocomposite prepared from carbon spheres (CSs; with an average diameter of 500 nm) that were synthesized from resorcinol and formaldehyde, and then were coated with gold nanoparticles (AuNPs) by chemically growing them of the CSs. Compared to a bare BDD electrode, the electron transfer resistance is lower on this new electrode. Compared to an electrode without Au-NPs, the peak potential is negatively shifted by 42 mV, and the peak current is increased by 55 %. This is ascribed to the larger surface in the AuNP-CS nanocomposite which improves the adsorption of AChE, enhances its activity, and facilitates electrocatalysis. Under optimum conditions, the inhibitory effect of chlorpyrifos is linearly related to the negative log of its concentration in the 10^?11 to 10^?7 M range, with a detection limit of 1.3?×?10^?13 M. For methyl parathion, the inhibition effect is linear in the 10^?12 to 10^?6 M range, and the detection limit is 4.9?×?10^?13 M. The biosensor exhibits good precision and acceptable operational and temporal stability.

Quantum dot induced phototransformation of 2,4-dichlorophenol, and its subsequent chemiluminescence reaction

We have studied the CdTe quantum dot-induced phototransformation of 2,4-dichlorophenol (2,4-DCP) and its subsequent chemiluminescence (CL) reaction. Quantum dots (QDs) of different size and capped with thioglycolic acid were prepared and characterized by molecular spectroscopy, X-ray diffraction and transmission electron microscopy. In the presence of QDs, 2,4-DCP is photochemically transformed into a long-living light emitting precursor which can react with N-bromosuccinimide to produce CL with peak wavelengths at 475 and 550 nm. The formation of singlet oxygen during the phototransformation process was confirmed by the enhancement effect of deuterium oxide on the CL reaction and the change in the UV spectrum of a chemical trap. The CL intensity is linearly related to the concentration of 2,4-DCP in the range from 0.36 to 36 μmol L^?1, and the detection limit (at 3σ) is 0.13 μmol L^?1.

Simple optical determination of silver ion in aqueous solutions using benzo crown-ether modified gold nanoparticles

We describe a method for the modification of gold nanoparticles (Au-NPs) with benzo-15-crown-5 that led to the development of a colorimetric assay for Ag(I) ion. The brown color of a solution of the modified Au-NPs turns to purple on addition of Ag(I) ion. The ratio of the UV–vis absorption at 600 nm and 525 nm is proportional to the concentration of Ag(I) ions in the range from 20 to 950 nM, and the detection limit is 12.5 nM. Other metal ions do not interfere if present in up to millimolar concentrations. The method enables a rapid determination of Ag(I) in lake and drinking water and is amenable to bare-eye readout.

Continuous flow synthesis and characterization of tailor-made bare gold nanoparticles for use in SERS

We describe a method for the synthesis of gold nanoparticles in a stainless steel continuous flow tubular reactor using tetrachloroauric acid as a precursor but without using a classical reducing agent. Gold(III) ion is reduced by stainless steel to form gold nanoparticles which are collected at the end of the coil. A single-phase system is introduced that generates dispersed nanoparticles in the absence of reducing agents on their surface. By controlling flow rates and temperature, the size of the nanoparticles can be tuned in the range from 24 nm to 36 nm. The reproducibility of the preparation was investigated, relative standard deviation of both the wavelength of the peak and the intensity of the plasmonic absorption band were determined and found to vary by 0.15 % and 6.5 %, respectively. Flow synthesis is found to be an excellent alternative to chemical methods to produce stable gold nanoparticles of varying size in an efficiently way. The particles obtained also perform very well when used as a substrate in surface enhanced Raman scattering as shown by the characterization of carboxylated single walled carbon nanotubes.

Solvent extraction of europium trifluoromethanesulfonate into nitrobenzene by using three electroneutral receptors

From extraction experiments and $ \gamma $ -activity measurements, the extraction constants corresponding to the general equilibrium Eu³⁺(aq) + 3 A^?(aq) + L(nb) $ \Leftrightarrow $ EuL³⁺(nb) + 3A^?(nb) taking place in the two-phase water–nitrobenzene system ( $ {\text{A}}^{ - } = {\text{CF}}_{ 3} {\text{SO}}_{3}^{ - } $ ; L = electroneutral receptors denoted by 1, 2, and 3 – see Scheme 1; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the EuL³⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the series of 3 < 2 < 1.

Tetraphenylantimony(V) O,O′-dialkyl dithiophosphates [Sb(C6H5)4{S2P(OR)2}] (R = s-C4H9, c-C6H11): Synthesis, structures, and 13C and 31P CP/MAS NMR spectra

Tetraphenylantimony(V) O,O′-di-sec-butyl dithiophosphate (I) and tetraphenylantimony(V) O,O′-dicyclohexyl dithiophosphate (II) [Sb(C₆H₅)₄{S₂P(OR)₂}] (R = sec-C₄H₉ or cyclo-C₆H₁₁) were obtained. Their structures and spectroscopic properties were studied by X-ray diffraction analysis and ¹³C and ³¹P CP/MAS NMR spectroscopy. The dithiophosphate (Dtph) ligands in complexes I and II were found to be coordinated in S-monodentate and S,S′-bidentate fashions, respectively (MAS NMR data). According to X-ray diffraction data, the coordination polyhedron of antimony in molecular structure I is a trigonal bipyramid with unusual monodentate coordination of the Dtph group in the axial position.     

Effects of type of nanosized carbon black on the performance of an all-solid-state potentiometric electrode for nitrate

The potentiometric properties of all-solid-state nitrate-selective electrodes based on plasticized PVC and containing different types of nanosized carbon black were investigated. The use of a carbon black interlayer is shown to significantly improve the potentiometric response. The electrodes display a close-to-Nernstian slope in the range from 10^?1 to 10^?6 M, highly stable potentials and low membrane resistance. However, different analytical features were found depending on the type of carbon black used. The best long-term potential stability was observed for the electrode with Printex XE2-B carbon black that has a relatively high BET surface area (1000 m²?·?g^?1) and an average particle size of 30 nm. Nevertheless, the electrodes with the Vulcan XC-72 (BET surface: 240 m²?·?g^?1; average size: 55 nm) showed the most repeatable and reproducible standard potential. The lowest detection limit for nitrate (2.5·10^?7 M) is observed for an electrode containing Vulcan XC-72.

Synthesis and application of a thermosensitive tri-block copolymer as an efficient sample treatment technique for preconcentration and ultra-trace detection of lead ions

We have designed and synthesized a thermosensitive tri-block copolymer for selective trace extraction of Pb(II) ions from biological and food samples. The polymer was characterized by Fourier transform IR and NMR spectroscopy, and by gel permeation chromatography. The critical aggregation concentration and lower critical solution temperature were determined via fluorescence and UV spectrophotometry, respectively. The effects of solution pH value, amount of copolymer, of the temperature on extraction and on phase separation, and of the matrix on the extraction of Pb(II) were optimized. Pb(II) ions were then quantified by FAAS. The use of this copolymer resulted in excellent figures of merit including a calibration plot extending from 0.5 to 160 μg L^?1 (with an R² of >0.99), a limit of detection (LOD) as low as 90 pg L^?1, an extraction efficiency of >98 %, and relative standard deviations of <4 % for eight separate extraction experiments.

The development and optimization of a modified single-drop microextraction method for organochlorine pesticides determination by gas chromatography-tandem mass spectrometry

We have developed a new method for single-drop microextraction (SDME) for the preconcentration of organochlorine pesticides (OCP) from complex matrices. It is based on the use of a silicone ring at the tip of the syringe. A 5 μL drop of n-hexane is applied to an aqueous extract containing the OCP and found to be adequate to preconcentrate the OCPs prior to analysis by GC in combination with tandem mass spectrometry. Fourteen OCP were determined using this technique in combination with programmable temperature vaporization. It is shown to have many advantages over traditional split/splitless injection. The effects of kind of organic solvent, exposure time, agitation and organic drop volume were optimized. Relative recoveries range from 59 to 117 %, with repeatabilities of <15 % (coefficient of variation) were achieved. The limits of detection range from 0.002 to 0.150 μg kg^?1. The method was applied to the preconcentration of OCPs in fresh strawberry, strawberry jam, and soil.