Comparison of different liquid chromatography stationary phases in LC-HRMS metabolomics for the detection of recombinant growth hormone doping control

Growth hormone (GH) is a polypeptide suspected of being used in horse racing to speed up physical performances. Despite scientific advances in the recent years, the control of its administration remains difficult. In order to improve it, a metabolomics study through LC-high resolution mass spectrometry measurements was recently initiated to assess the metabolic perturbations caused by recombinant equine growth hormone administration. Few tens of ions not identified structurally were highlighted as compounds responsible for the modification of metabolic profiling observed in treated animals. This previous work was based on the use of Uptisphere Strategy NEC as the chromatographic column. In parallel, more and more metabolomics studies showed the interest of the use of new chromatographic supports such as hydrophilic interaction chromatography for the analysis of polar compounds. It is in this context that an investigation was conducted on Uptisphere HDO and Luna hydrophilic interaction chromatography stationary phases to generate and process urinary metabolomics fingerprints, which could allow to establish a comparison with Uptisphere Strategy NEC. The chromatographic column the most adapted for the detection of new biomarkers of GH administration has been used to set up a relevant statistical model based on the analysis of more than hundred biological samples.     

Preparation and characterization of Zonyl-coated nanodiamonds with antifouling properties

The paper reports on covalent linking of a modified amphiphilic polymer, the alkynyl-terminated Zonyl, to azide-terminated nanodiamonds by click chemistry. An analysis of the hybrid particle stability is presented based on size and zeta potential measurements. The antifouling character of the grafted nanodiamonds was investigated using bovine serum albumin as a model protein. The protein adsorption was quantified using a Bradford assay and found to be reduced by 30% in the presence of the Zonyl layer.     

Characterization,optical and thermal properties of new azomethines based on heptadecafluoroundecyloxy benzaldehyde

New thermotropic liquid crystals containing a long alkoxysemiperfluorinated chain (-O-(CH₂)₃-(CF₂)₇-CF₃), one linking unit in mesogenic cores (HC=N-) and different functional end-groups such as 4-hexadecyl-, 4-n-hexadecyloxy- chain, or biphenyl-4-carbonitrile, 4-diazenyl-N,N-dimethylbenzene or pyren were synthesized via a one-step route. The methods of nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), ultraviolet–visual (UV-vis) and photoluminescence (PL) spectroscopy as well as differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) were used. The absorption (UV-vis) and PL features of all compounds are documented. The amine had an effect on the mesomorphic properties of the azomethines. An enantiotropic smectic phase was observed for all of the systems studied. As a result of DSC and POM investigations, it is shown that liquid crystalline properties of the azomethines exhibit a strong dependence of the end-groups. The mesomorphic behaviour of the compounds was investigated also by FTIR(T) and UV-vis(T) spectroscopy. Current–voltage measurements were performed on an ITO/compound/Alq₃/Al device.     

Geometric measures of large biomolecules: surface, volume, and pockets

Geometry plays a major role in our attempts to understand the activity of large molecules. For example, surface area and volume are used to quantify the interactions between these molecules and the water surrounding them in implicit solvent models. In addition, the detection of pockets serves as a starting point for predictive studies of biomolecule-ligand interactions. The alpha shape theory provides an exact and robust method for computing these geometric measures. Several implementations of this theory are currently available. We show however that these implementations fail on very large macromolecular systems. We show that these difficulties are not theoretical; rather, they are related to the architecture of current computers that rely on the use of cache memory to speed up calculation. By rewriting the algorithms that implement the different steps of the alpha shape theory such that we enforce locality, we show that we can remediate these cache problems; the corresponding code, UnionBall has an apparent O(n) behavior over a large range of values of n (up to tens of millions), where n is the number of atoms. As an example, it takes 136 sec with UnionBall to compute the contribution of each atom to the surface area and volume of a viral capsid with more than five million atoms on a commodity PC. UnionBall includes functions for computing analytically the surface area and volume of the intersection of two, three and four spheres that are fully detailed in an appendix. UnionBall is available as an OpenSource software.     

Adsorption of multilamellar tubes with a temperature tunable diameter at the air/water interface

The ethanolamine salt of 12-hydroxy stearic acid is known to form tubes having a temperature tunable diameter. Here, we study the behavior of those tubes at the air/water interface by using Neutron Reflectivity. We observed that tubes indeed adsorbed at this interface below a fatty acid monolayer and exhibit the same temperature behavior as in bulk. There is however a peculiar behavior at around 50 °C for which the increase of the diameter of the tubes at the interface yields an unfolding of those tubes into a multilamellar layer. Upon further heating, the tubes re-fold and their diameter re-decreases after which they melt into micelles as observed in the bulk. All structural transitions at the interface are nevertheless reversible. This provides to the system a high interest for its interfacial properties because the structure at the air/water interface can be tuned easily by the temperature.     

Continuous-wave quantum cascade lasers absorption spectrometers for trace gas detection in the atmosphere

Mid infra-red absorption spectrometry based on continuous-wave distributed feedback (DFB) quantum cascade laser (QCL) is more and more widely used for trace gas detection and pollution monitoring. The main advantages of this technique are high sensitivity, high selectivity and a potential for extreme compactness. Various examples of trace gas detection for atmospheric detection will be presented in this paper. Commercial QCLs available on the shelves were first implemented. A cryogenic QCL emitting at 6.7 μm was used to demonstrate the detection of water vapor and its isotopes. A room-temperature QCL was then used to simultaneously detect methane and nitrous oxide at 7.9 μm. Recently, we have developed a room-temperature top grating DFB QCL designed around 4.5 μm for the demonstration of N₂O detection in the ppb range. Atmospheric applications of these spectrometers will be presented. The improvements of QCL performances make it now possible to develop instruments that are more and more compact and therefore compatible with in situ applications.     

Role of Nuclear Factor-KB in Colon Cancer Cell Apoptosis Mediated by Aminopyropheophorbide Photosensitization

Aminopyropheophorbide (APP) is a second generation of photosensitizer for photodynamic therapy (PDT). We demonstrated that APP strongly absorbed red light and, after being taken up by colon cancer cells (HCT-116 cells), was localized in cytoplasmic and internal membranes but not in mitochondria. The APP-mediated photosensitization was cytotoxic for HCT-116 cells through an induction of apoptosis. Indeed, DNA fragmentation (DNA laddering and terminal deoxyuridine nick-end labeling) and chromatin condensation (4',6-diamidine-2'-phenylindole staining) could be visualized soon after photosensitization. Because nuclear factor (NF)-kappa B is involved in the response to many photosensitizers, we also demonstrated its nuclear translocation in two waves: a rapid and transient one, followed by a slow and sustained phase. The NF-kappa B turned out to be involved in an antiapoptotic response to APP-mediated photosensitization because the HCT-116 cell line expressing the dominant negative mutant of inhibitor-kappa B alpha was more sensitive to apoptosis as measured by DNA fragmentation and caspase activation. These data unambiguously show that a membrane-located photosensitizer can lead to effective apoptosis, reinforcing the idea that PDT can be an effective means to eradicate colon cancer cells.     

Determination of Fluorescence Yields, Singlet Lifetimes and Singlet Oxygen Yields of Water-Insoluble Porphyrins and Metalloporphyrins in Organic Solvents and in Aqueous Media

Abstract— Fluorescence quantum yields and singlet lifetimes for a wide range of hydrophilic to hydrophobic porphyrins and metalloporphyrins have been determined in toluene, methanol or acetone. Photosensitized singlet oxygen yields have been determined in the same solvents. For some porphyrins, the same quantities were determined in an aqueous medium, through use of an amphiphilic polymer to solubilize the porphyrin sensitizer and target molecule, 1, 3-diphenylisobenzofuran. Because rate constants for the deactivation of singlet oxygen ( k _d) and for its reaction with a target molecule (k _a ) are unknown in such aqueous polymer systems, a new method was developed for evaluating yields of singlet oxygen formation that also provides a value for the ratio k_d/k_a. A variation observed in quantum yield of singlet oxygen production for the aqueous polymer system with variation in initial concentration of the target molecule is discussed.     

Transition-Metal-Catalyzed Carbenoid Reactions of Sulfonium Ylides

Olefins undergo cyclopropanation with diphenylsulfonium (ethoxycarbonyl)methylide (=diphenylsulfonium 2-ethoxy-2-oxoethylide; 3a ) in the presence of chiral Cu^I or Rh^II catalysts. trans/cis Ratios and ee's of the cyclopropanes 6 obtained with this ylide in the presence of a chiral Cu^I catalyst 7 are identical with those obtained with ethyl diazoacetate ( 4 ). In the case of catalysis with Rh^II, the trans/cis ratios of the cyclopropanes as well as the enantioselectivity change slightly upon going from the ylide 3a to diazoacetate 4 .