A thienoquinoxaline and a styryl-quinoxaline as new fluorescent probes for amyloid-β fibrils

Simple and easy to prepare quinoxaline derivatives proved able to stain amyloid fibers such as aggregated lysozyme and Aβ(1-40)-peptide by a fluorescence “turn on” mechanism. Thienoquinoxaline 1 allowed the detection of lysozyme and Aβ(1-40) fibers at λ = 555 and 532 nm, respectively, with excitation at λ = 450 nm. Styryl-quinoxaline 2 stained lysozyme and Aβ(1-40) fibers with fluorescence at λ = 579 and 567 nm, respectively, upon excitation at λ = 453 nm. The apparent K_d values for Aβ(1-40) fibers were 77 and 294 nM for 1 and 2, respectively. The sensitivity of the aggregates detection assay with these new dyes was higher than that of thioflavin T. Considering their unique fluorescence properties compared to other dyes reported in the field, they can be considered as additional staining tools for the detection and studies of peptide/protein aggregation.     

Terahertz spectroscopy: a powerful new tool for the chemical sciences?

Terahertz spectroscopy is only now beginning to make its transition from initial development by physicists and engineers to broader use by chemists, materials scientists and biologists, thanks to the increasing availability of commercial terahertz spectrometers. With the unique insights that terahertz spectroscopy can provide into intermolecular bonding and crystalline matter, it could prove to be an invaluable addition to the chemist's analytical toolset. This tutorial review aims to give an introduction to terahertz spectroscopy, its techniques, equipment, current applications and potential for the chemical sciences to a broad readership.     

Droplet microfluidics with magnetic beads: a new tool to investigate drug–protein interactions

In this study, we give the proof of concept for a method to determine binding constants of compounds in solution. By implementing a technique based on magnetic beads with a microfluidic device for segmented flow generation, we demonstrate, for individual droplets, fast, robust and complete separation of the magnetic beads. The beads are used as a carrier for one binding partner and hence, any bound molecule is separated likewise, while the segmentation into small microdroplets ensures fast mixing, and opens future prospects for droplet-wise analysis of drug candidate libraries. We employ the method for characterization of drug–protein binding, here warfarin to human serum albumin. The approach lays the basis for a microfluidic droplet-based screening device aimed at investigating the interactions of drugs with specific targets including enzymes and cells. Furthermore, the continuous method could be employed for various applications, such as binding assays, kinetic studies, and single cell analysis, in which rapid removal of a reactive component is required.     

Separation of dansylated 17β-estradiol, 17α-estradiol, and estrone on a single HPLC column for simultaneous quantitation by LC–MS/MS

We show here that baseline separation of dansylated estrone, 17β-estradiol, and 17α-estradiol can be done, contrary to previous reports, within a short run time on a single RP-LC analytical column packed with particles bonded with phenyl-hexyl stationary phase. The chromatographic method coupled with isotope dilution tandem MS offers a simple assay enabling the simultaneous analysis of these analytes. The method employs ¹³C-labeled estrogens as internal standards to eliminate potential matrix effects arising from the use of deuterated estrogens. The assay also offers adequate accuracy and sensitivity to be useful for biological samples. The practical applicability of the validated method is demonstrated by the quantitative analyses of in vivo samples obtained from rats treated with Premarin®.

Molecular recognition of endocrine disruptors by synthetic and natural 17β-estradiol receptors: a comparative study

A β-estradiol receptor binding mimic was synthesised using molecular imprinting. Bulk polymers and spherical polymer nanoparticles based on methacrylic acid and ethylene glycol dimethacrylate as the functional monomer and crosslinker, respectively, were prepared in acetonitrile. The selectivity was evaluated by radioligand binding assays. The imprinted polymers were very specific to β-estradiol since the control polymers bound virtually none of the radioligand. The bulk polymer was then employed to screen endocrine disrupting chemicals. Structurally related steroids like α-estradiol, estrone and ethynylestradiol showed, respectively, 14.0, 5.0 and 0.7% of relative binding to the β-estradiol polymer, whereas most unrelated chemicals did not bind at all. These results are compared to those obtained with a bioassay using stably transfected yeast cells in culture bearing the human estrogen receptor. The receptor was activated by several estrogen-like chemicals and to a lesser extent by some structurally related chemicals. Figure A molecularly imprinted polymer that was a synthetic receptor for beta-estradiol was used for the screening of endocrine disrupting chemicals that are structurally related or unrelated to beta-estradiol. The results were compared with the recognition of the compounds by the biological estrogen receptor expressed in yeast cells. Related steroids like alpha-estradiol, estrone and ethynylestradiol showed significant binding to the beta-estradiol imprinted polymer, whereas most unrelated chemicals did not bind. The biological receptor was activated by several estrogen-like chemicals, and to a lesser extent by some structurally related chemicals     

Etodolac:β-cyclodextrin inclusion complex as a novel fluorescent chemosensor probe for Ba2+

The inclusion complex of etodolac (ETD) with β-CD was investigated by UV-visible and fluorescence spectroscopy. The chemosensory ability of ETD:β-CD complex for various metal cations was investigated thoroughly, and we found that the emission of the complex showed a drastic increase in the intensity for Ba²⁺. Competitive experiments of ETD:β-CD complex with Ba²⁺ showed that no significant variation was found in the fluorescence intensity of the ETD:β-CD/Ba²⁺ complex upon adding other cations, such as Na⁺, Ag⁺, Hg²⁺, Cd²⁺, Al³⁺, Cr³⁺, Fe³⁺, Se⁴⁺, and Ti⁴⁺. The linearity range, limit of detection (LOD), and limit of quantitation (LOQ) were determined from the selectivity and sensitivity studies.     

Tetra-β-nitro-substituted phthalocyanines: a new organic electrode material for lithium batteries

Tetra-β-nitro-substituted nickel phthalocyanine (TN-NiPc) and hollow phthalocyanine (TN-H₂Pc) were synthesized and investigated as novel organic electrode materials for rechargeable lithium batteries. After the two H atoms in the center of TN-H₂Pc were replaced with Ni atoms, the interactive force between the phthalocyanine rings was reduced, which resulted in a fluffy morphology for the TN-NiPc that was beneficial to the transition of Li⁺. As a result, better electrochemical properties and reversibility were observed in the TN-NiPc electrodes compared to the TN-H₂Pc electrode. The capacity of TN-NiPc electrode was stable at about 280 mAh g^?1 at 0.2 C after 250 cycles at several different current rates of 0.1, 0.2, 0.5, and 1 C. The TN-NiPc based cathode materials may provide new opportunities for organic, flexible, and stable secondary lithium batteries.

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Graphical Abstract The TN-NiPc electrode shows better electrochemical properties than that of TN-H ₂ Pc electrode, which is due to the strong hydrogen bond interaction and π-π interaction of TN-H ₂ Pc molecules, resulting in more dense stacking degree of the phthalocyanine ring and restricting the transport of Li⁺ .

     

Molecularly imprinted solid-phase extraction for the selective determination of 17β-estradiol in fishery samples with high performance liquid chromatography

A molecularly imprinted polymer (MIP) has been synthesized by a thermo-polymerization method using methacrylic acid (MAA) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linker, acetonitrile as porogenic solvent, and 17β-estradiol as template. The MIP showed obvious affinity for 17β-estradiol in acetonitrile solution, which was confirmed by absorption experiments. After optimization of molecularly imprinted solid-phase extraction (MISPE) conditions, three structurally related estrogenic compounds (17β-estradiol, estriol, and diethylstilbestrol) were used to evaluate the selectivity of the MIP cartridges. The MIP cartridges exhibited highly selectivity for E₂, the recoveries were 84.8 ± 6.53% for MIPs and 19.1 ± 1.93% for non-imprinted polymer (NIP) cartridges. The detection and quantification limits correspond to 0.023 and 0.076 mg L⁻¹. Furthermore, the MISPE methods were used to selectively extract E₂ from fish and prawn tissue prior to HPLC analysis. This MISPE-HPLC procedure could eliminate all matrix interference simultaneously and had good recoveries (78.3-84.5%).     

β-Sonogel-Carbon electrodes: A new alternative for the electrochemical determination of catecholamines

In this work, a new alternative for the electrochemical determination of catecholamines based on β-cyclodextrin-Sonogel-Carbon electrodes is reported. The incorporation of β-CD and graphite in the preparation of the Sonogel-Carbon material leads to a modification of the electrode surface properties which causes a significant increase in the oxidation peak current of biomolecules such as dopamine, l-epinephrine, d,l-norepinephrine and catechol. This phenomenon might be attributed to the formation of an inclusion complex between β-CD and the catecholamines. The amount of β-CD necessary to form the Sonogel electrode was studied and optimization of electrochemical parameters, perm selectivity and mechanical stability of the sensor are discussed. Scanning electron microscopy and electrochemical impedance spectroscopy measurements were employed to characterize the electrical parameters and the structural properties of the new electrode surface, respectively. Cyclic voltammetry (CV) and Adsorptive differential pulse voltammetry (AdDPV) measurements were also used to explore the electrochemical behaviour of the electrode versus the quoted catecholamines. The β-CD-Sonogel-Carbon electrode offers fast and linear responses towards dopamine, norepinephrine, epinephrine and catechol, with good and low detection limits: 0.164, 0.294, 0.699 and 0.059 μmol L⁻¹, respectively.     

Synthesis and photoluminescence properties of π-extended fluorene derivatives: the first example of a fluorescent solvatochromic nitro-group-containing dye with a high fluorescence quantum yield

Functional π-extended fluorene derivatives, 2,7-di(p-substituted-phenyl)fluorenes containing different functional groups such as hydrogen, trimethylsilyl (TMS), methoxycarbonyl, cyano, and nitro groups, were synthesized. Except for the nitro group, the resulting compounds exhibited extremely high fluorescence quantum yields (Φ_F >0.85 in chloroform). The diphenylfluorene containing nitro groups have higher fluorescence quantum yield (Φ_F = 0.31 in N,N’-dimethyl-formamide) than other nitro-group-containing fluorophores which were previously reported (Φ_F <0.1). Furthermore, this compound exhibited large Stokes’ shift with green to orange emission and unique on-off behavior of the emission by solvents.     

β-Trimethylsilylethanesulfonyl chloride (SES-Cl): A new reagent for protection of amines

The title compound, easily prepared in two steps from vinyltrimethylsilane, is a useful reagent for the protection of primary and secondary amines as their sulfonamides, which are cleaved by fluoride ion.     

2H stable isotope analysis of human tooth enamel: a new tool for forensic human provenancing?

Stable isotope analysis of biogenic tissues such as tooth enamel and bone mineral has become a well-recognised and increasingly important method for determining the provenance of human remains, and it has been used successfully in bio-archaeological studies as well as forensic investigations. In particular, (18)O and (2)H stable isotope signatures of bone and hair, respectively, are well-established proxies of climate (temperature) and source water and are therefore considered as indicators of geographic life trajectories of animals and humans. While the methodology for (2)H analysis of human hair, fingernails, and bone collagen is currently used to determine human provenance, i.e. geographic origin and identify possible migration patterns, studies involving the analysis of (2)H in tooth enamel appear to be nonexistent in the scientific literature. Ground tooth enamel was analysed by continuous-flow isotope ratio mass spectrometry (IRMS) coupled on-line to a high-temperature conversion elemental analyser (TC/EA). An array of tooth enamel samples from archaeological and modern teeth has been analysed under different experimental conditions, and the results of this proof-of-concept study are presented. While no significant differences in (2)H abundance were noted as a result of H exchange studies or different sample preparation protocols, no significant differences or trends in measured δ(2)H-values were observed either with regard to known differences in geographical provenance. We concluded that the δ(2)H-values obtained from tooth enamel could not be used as proxy for a person's geographical origin during adolescence.     

A new sesquiterpene with a novel 1β, 8β-oxygen bridge from Heteropappus altaicus (willd.) Novopokr

A new guaiane-type sesquiterpene, 4α,7β-dihydroxy-10βH-guai-5-en-1β,8β-endoxide (1), was isolated from Heteropappus altaicus (Compositea). The structure of compound 1, which contains exhibited a rare 1,8-oxide bridge, was established on the basis of spectroscopic data.     

A fluorescent turn-on detection scheme for α-fetoprotein using quantum dots placed in a boronate-modified molecularly imprinted polymer with high affinity for glycoproteins

This article describes a fluorescent molecularly imprinted polymer (MIP) capable of selective fluorescent turn-on recognition of the tumor biomarker α-fetoprotein. The technique is making use of amino-modified Mn-doped ZnS quantum dots (QDs) as solid supports, 4-vinylphenylboronic acid and methyl methacrylate as the functional monomers, γ-methacryloxypropyl trimethoxysilane as the grafting agent, and α-fetoprotein as a template. A graft imprint is created on the surface of the QDs. The functional monomers are shown to play an important role in the formation of the binding sites and in preventing nonspecific protein binding. The resulting MIP-QDs display a good linear response to α-fetoprotein in the 50 ng · L⁻¹ to 10 μg · L⁻¹ concentration range, and the limit of detection is 48 ng · L⁻¹. In our perception, the method has a wide scope in that it may be adapted to various other glycoproteins.

Schematic illustration of the synthesis of the MIP-QDs composites

     

Carbonyl olefination with a-stannyl ester enolates: A new synthesis of α,β-unsaturated esters

The reaction of α-stannyl ester enolates with carbonyl compounds is described. α,β-Unsaturated esters are obtained in good yields. A reaction mec     

A new method for loading mesoporous silica nanoparticles with drugs: Sol–gel synthesis using drug micelles as a template

It has been shown that mesoporous nanocontainers from SiO₂ may be obtained by the sol–gel synthesis using drug (Miramistin) micelles as a template. The nanocontainers resulting from the combination of the stages of their synthesis and loading are characterized by a very high content of the drug (no less than 0.9 g per 1 g of SiO₂). The kinetics of Miramistin desorption from the mesoporous particles into an aqueous medium has been studied under static and quasi-dynamic conditions. The desorption has been shown to rather strongly depend on pH. Possible mechanisms of the desorption process have been discussed.     

A new use for an old molecule: N-phenyl-2-(2-hydroxynaphthalen-1-ylmethylene)hydrazinecarbothioamide as a ratiometric ‘Off–On’ fluorescent probe for iron

N-Phenyl-2-(2-hydroxynaphthalen-1-ylmethylene)hydrazinecarbothioamide has been investigated as a fluorescent sensor for the determination of Fe(III) in aqueous solutions. The probe was prepared by the facile Schiff base condensation of 2-hydroxy-1-napthaldehyde with N-phenylhydrazinecarbothioamide. The sensor displayed good selectivity for Fe(III) when tested against a range of biologically and environmentally important cations. A concentration dependent increase in the emission of two fluorescent bands at 425 and 495 nm was observed upon increasing Fe(III) addition resulting in a linear ratiometric response in the 17–37 μM range. The binding stoichiometry was confirmed as 1:1 (host/guest) with the binding constant (log β) calculated as 4.56.