Aqueous Photocatalytic Oxidation of Thioethers with Polydiacetylene Micelle Nanoreactors.

A semi-heterogeneous photocatalytic system was assembled through encapsulation of a lipophilic porphyrin in stabilized polydiacetylene micelles. The colloidal nanohybrid catalyst was valorized in the aerobic photo-oxidation of sulfides to the corresponding sulfoxides. Micelles behaved as nanoreactors by creating a favorable environment for the photo-activation of oxygen nearby thioethers and subsequent sulfoxidation.

Interplay of structure and photophysics of individualized rod-shaped graphene quantum dots with up to 132 sp² carbon atoms.

Nanographene materials are promising building blocks for the growing field of low-dimensional materials for optics, electronics and biophotonics applications. In particular, bottom-up synthesized 0D graphene quantum dots show great potential as single quantum emitters. To fully exploit their exciting properties, the graphene quantum dots must be of high purity; the key parameter for efficient purification being the solubility of the starting materials.

General Guidelines for Sample Preparation Strategies in HR-µMAS NMR-based Metabolomics of Microscopic Specimens.

The study of the metabolome within tissues, organisms, cells or biofluids can be carried out by several bioanalytical techniques. Among them, nuclear magnetic resonance (NMR) is one of the principal spectroscopic methods. This is due to a sample rotation technique, high-resolution magic angle spinning (HR-MAS), which targets the analysis of heterogeneous specimens with a bulk sample mass from 5 to 10 mg.

Single-Scan Diffusion-Ordered NMR Spectroscopy of SABRE-Hyperpolarized Mixtures.

The analysis of complex mixtures of dissolved molecules is a major challenge, especially for systems that gradually evolve, e. g., in the course of a chemical reaction or in the case of chemical instability.

HR-μMAS NMR-Based Metabolomics: Localized Metabolic Profiling of a Garlic Clove with μg Tissues.

The localization of metabolic profiles within a tissue sample is of particular interest when the sampling size is considerably small, i.e., in the order of a microgram (μg) scale.

Functionalization of Bambusurils by a Thiol-Ene Click Reaction and a Facile Method for the Preparation of Anion-Free Bambus[6]urils.

Sulfide-functionalized bambus[4]urils ((RS) BU[4]) and bambus[6]urils ((RS) BU[6]) were synthesized through thiol-ene click coupling reactions (TEC) of allylbambus[n]urils. Thiosugars were grafted to BU[4] and BU[6]. Synthesis of BU[6] derivatives always requires the use of a template anion (iodide, chloride, or bromide), which is enclosed in the cavity of BU[6].

Unsaturated cryptophanes: Toward dual PHIP/hyperpolarised xenon sensors.

Cryptophanes, cage-molecules constituted of aromatic bowls, are now well recognised as powerful xenon hosts in Xe NMR-based biosensing. In the quest of a dual probe that can be addressed only by NMR, we have studied three cryptophanes bearing a tether with an unsaturated bond. The idea behind this is to build probes that can be detected both via hyperpolarised Xe NMR and para-hydrogen induced polarisation H NMR.

Metabolomic and proteomic investigations of impacts of titanium dioxide nanoparticles on Escherichia coli.

In a previous study, it was demonstrated that the toxic impact of titanium dioxide nanoparticles on Escherichia coli starts at 10 ppm and is closely related to the presence of little aggregates. It was also assumed that only a part of the bacterial population is able to adapt to this stress and attempts to survive. Proteomic analyses, supported by results from metabolomics, reveal that exposure of E.

Nuclear spin noise in NMR revisited.

The theoretical shapes of nuclear spin-noise spectra in NMR are derived by considering a receiver circuit with finite preamplifier input impedance and a transmission line between the preamplifier and the probe. Using this model, it becomes possible to reproduce all observed experimental features: variation of the NMR resonance linewidth as a function of the transmission line phase, nuclear spin-noise signals appearing as a "bump" or as a "dip" superimposed on the average electronic noise level even for a spin system and probe at the same temperature, pure in-phase Lorentzian spin-noise signals exhibiting non-vanishing frequency shifts. Extensive comparisons to experimental measurements validate the model predictions, and define the conditions for obtaining pure in-phase Lorentzian-shape nuclear spin noise with a vanishing frequency shift, in other words, the conditions for simultaneously obtaining the spin-noise and frequency-shift tuning optima.

Single-Scan Multidimensional NMR Analysis of Mixtures at Sub-Millimolar Concentrations by using SABRE Hyperpolarization.

Signal amplification by reversible exchange (SABRE) is a promising method to increase the sensitivity of nuclear magnetic resonance (NMR) experiments. However, SABRE-enhanced (1)H NMR signals are short lived, and SABRE is often used to record 1D NMR spectra only. When the sample of interest is a complex mixture, this results in severe overlaps for (1)H spectra.

On the tuning of high-resolution NMR probes.

Three optimum conditions for the tuning of NMR probes are compared: the conventional tuning optimum, which is based on radio-frequency pulse efficiency, the spin noise tuning optimum based on the line shape of the spin noise signal, and the newly introduced frequency shift tuning optimum, which minimizes the frequency pushing effect on strong signals. The latter results if the radiation damping feedback field is not in perfect quadrature to the precessing magnetization. According to the conventional RLC (resistor-inductor-capacitor) resonant circuit model, the optima should be identical, but significant deviations are found experimentally at low temperatures, in particular on cryogenically cooled probes.

Cell uptake of a biosensor detected by hyperpolarized 129Xe NMR: the transferrin case.

For detection of biological events in vitro, sensors using hyperpolarized (129)Xe NMR can become a powerful tool, provided the approach can bridge the gap in sensitivity. Here we propose constructs based on the non-selective grafting of cryptophane precursors on holo-transferrin. This biological system was chosen because there are many receptors on the cell surface, and endocytosis further increases this density.

A water-soluble Xe@cryptophane-111 complex exhibits very high thermodynamic stability and a peculiar (129)Xe NMR chemical shift.

The known xenon-binding (±)-cryptophane-111 (1) has been functionalized with six [(η(5)-C(5)Me(5))Ru(II)](+) ([Cp*Ru](+)) moieties to give, in 89% yield, the first water-soluble cryptophane-111 derivative, namely [(Cp*Ru)(6)1]Cl(6) ([2]Cl(6)). [2]Cl(6) exhibits a very high affinity for xenon in water, with a binding constant of 2.9(2) × 10(4) M(-1) as measured by hyperpolarized (129)Xe NMR spectroscopy.

Nuclear spin-noise spectra of hyperpolarized systems.

Spin-noise appeal: Detection of NMR spin-noise is very appealing when dilute hyperpolarized species are considered. Continuous monitoring of the noise absorption at the Larmor frequency enables determination of T(1) and T(2)*, independently of the static magnetic field. An inductively coupled microcoil located inside the NMR tube (see picture) allows acquisition of (129)Xe spin-noise spectra without radio-frequency excitation.

Cryptophane-xenon complexes in organic solvents observed through NMR spectroscopy.

The interaction of xenon with cryptophane derivatives is analyzed by NMR by using either thermal or hyperpolarized noble gas. Twelve hosts differing by their stereochemistry, cavity size, and the nature and the number of the substituents on the aromatic rings have been included in the study, in the aim of extracting some clues for the optimization of (129)Xe-NMR based biosensors derived from these cage molecules. Four important properties have been examined: xenon-host binding constant, in-out exchange rate of the noble gas, chemical shift, and relaxation of caged xenon.

Observation of noise-triggered chaotic emissions in an NMR-maser.

We report a new phenomenon observed when the magnetization of dissolved hyperpolarized (129)Xe is intense and opposite to the Boltzmann magnetization. Without radio-frequency (rf) excitation, the system spontaneously emits a series of rf bursts characterized by very narrow bandwidths (0.03 Hz at 138 MHz).

1H and 129Xe NMR absorption line shapes in the presence of highly polarized and concentrated xenon solutions in high magnetic field.

The presence of highly concentrated dissolved laser-polarized xenon (approximately 1mol/L, polarization up to 0.2) induces numerous effects on proton and xenon NMR spectra. We show that the proton signal enhancements due to (129)Xe-(1)H cross-relaxation (SPINOE) and overall shifts of the proton resonances due to the average dipolar shift created by the intense xenon magnetization are correlated.

Water soluble cryptophanes showing unprecedented affinity for xenon: candidates as NMR-based biosensors.

Cryptophanes bearing OCH(2)COOH groups in place of the methoxy groups represent a new class of xenon-carrier molecules soluble in water at biological pH. By using (1)H and (129)Xe NMR (thermally- and laser-polarized dissolved gas), the structural and dynamical behaviors of these host molecules as well as their interaction with xenon are studied. They are shown to exist in aqueous solution under different conformations in very slow exchange.

Study of the hydrophobic cavity of beta-cryptogein through laser-polarized xenon NMR spectroscopy.

The interaction of xenon with beta-cryptogein, a basic 10 kDa protein belonging to the elicitin family, has been studied by using dissolved thermal and laser-polarized gas in liquid-state NMR. 13C and 1H chemical-shift-mapping experiments were unfruitful, the proton lines only experienced a slight narrowing but no significant frequency variation when the xenon concentration was increased. Nevertheless magnetization transfer from hyperpolarized xenon to protons of the protein demonstrates an undoubted interaction and enables localization of the noble-gas-binding site.

Dynamics of xenon binding inside the hydrophobic cavity of pseudo-wild-type bacteriophage T4 lysozyme explored through xenon-based NMR spectroscopy.

Wild-type bacteriophage T4 lysozyme contains a hydrophobic cavity with binding properties that have been extensively studied by X-ray crystallography and NMR. In the present study, the monitoring of 1H chemical shift variations under xenon pressure enables the determination of the noble gas binding constant (K = 60.2 M(-1)).

Probing the hydrophobic cavity of lipid transfer protein from Nicotiana tabacum through xenon-based NMR spectroscopy.

The hydrophobic cavity of Lipid Transfer Protein 1 from Nicotiana tabacum is investigated in detail by NMR using xenon as a spy. The analysis of the (129)Xe chemical shifts and self-relaxation times gives evidence of protein-xenon interaction. Thermodynamics of the binding is characterized through the study of aliphatic (1)H and (13)C chemical shift variation as a function of xenon pressure.