Fast screening of anabolic steroids and other banned doping substances in human urine by gas chromatography/tandem mass spectrometry

A fast and sensitive method for the comprehensive screening of anabolic agents and other banned doping substances using gas chromatography/tandem mass spectrometry (GC/MS/MS) with an external ionization ion trap mass spectrometer is presented. The method takes advantage of the resolving power of MS/MS to eliminate background interferences, thus speeding up the chromatographic analysis. For each compound, different fragmentation reactions were studied and their collision energies optimized to obtain the best sensitivity in terms of their signal-to-noise ratio (S/N). A dramatic reduction in overall analysis time was achieved compared with other common approaches. More than 50 substances could finally be monitored in less than 7.4 min with detection limits (S/N >3) lower than 0.5 ng ml(-1) for most of the compounds with special sensitivity requirements according to the International Olympic Committee (IOC). A validation procedure for qualitative analysis was performed. The selectivity of the method showed that no interfering peaks were observed at the retention time of the analytes. Good intermediate precision, below 25% for most of the compounds, and robustness were observed. The optimized method was successfully applied to analyse more than 100 real human urine samples with optimum sensitivity and specificity rates.     

Electrospray ionization mass spectrometric fragmentation of hydroquinone derivatives

The fragmentation patterns of nine di-, tri- and tetracyclic hydroquinones with potential antitumor activity were rationalized by invoking competing mechanisms that included sterically accelerated homolytic cleavage, Meerwein-type rearrangements and dehydrations through elimination or intramolecular nucleophilic substitution.     

On the mechanism of the aza-Morita-Baylis-Hillman reaction: ESI-MS interception of a unique new intermediate

Solutions of aza-Morita-Baylis-Hillman (aza-MBH) reactions were directly monitored by ESI(+)-MS(/MS) spectrometry to obtain information on their mechanism. A unique bis-sulfonamide intermediate was intercepted and characterized and, based on this novel species, a mechanism that rationalizes the uniqueness of aza-MBH reactions is proposed.     

Interaction of cephalosporins with outer membrane channels of Escherichia coli. Revealing binding by fluorescence quenching and ion conductance fluctuations

Outer membrane channels in gram-negative bacteria are implicated in the influx of the latest generation of cephalosporins. We have measured the interaction strengths of ceftriaxone, cefpirome and ceftazidime in the two most abundant outer membrane porins of Escherichia coli, OmpF and OmpC, by both ion current fluctuations through single protein channels and fluorescence quenching. Statistical analysis of individual antibiotic entry events in membrane-incorporated porins yielded the kinetic rates and the equilibrium binding constant of each antibiotic-porin pair. Affinity constants were independently obtained by measuring the static quenching of inherent tryptophan fluorescence in the porins in the presence of the antibiotics. Through an empirical inner filter effect correction we have succeeded in measuring the chemical interaction of these strongly absorbing antibiotics, and obtained a qualitative agreement with conductance measurements. The interaction of all three antibiotics is smaller for OmpC than OmpF, and in the case of each porin the interaction strength series ceftriaxone > cefpirome > ceftazidime is maintained.     

Macrocybin,a Natural Mushroom Triglyceride,Reduces Tumor Growth In Vitro and In Vivo through Caveolin-Mediated Interference with the Actin Cytoskeleton

Mushrooms have been used for millennia as cancer remedies. Our goal was to screen several mushroom species from the rainforests of Costa Rica, looking for new antitumor molecules. Mushroom extracts were screened using two human cell lines: A549 (lung adenocarcinoma) and NL20 (immortalized normal lung epithelium). Extracts able to kill tumor cells while preserving non-tumor cells were considered “anticancer”. The mushroom with better properties was Macrocybe titans. Positive extracts were fractionated further and tested for biological activity on the cell lines. The chemical structure of the active compound was partially elucidated through nuclear magnetic resonance, mass spectrometry, and other ancillary techniques. Chemical analysis showed that the active molecule was a triglyceride containing oleic acid, palmitic acid, and a more complex fatty acid with two double bonds. The synthesis of all possible triglycerides and biological testing identified the natural compound, which was named Macrocybin. A xenograft study showed that Macrocybin significantly reduces A549 tumor growth. In addition, Macrocybin treatment resulted in the upregulation of Caveolin-1 expression and the disassembly of the actin cytoskeleton in tumor cells (but not in normal cells). In conclusion, we have shown that Macrocybin constitutes a new biologically active compound that may be taken into consideration for cancer treatment.     

Indene and pseudoazulene discotic liquid crystals: a synthetic and structural study

Several new liquid-crystalline indene and pseudoazulene systems are reported. These molecules give rise to either columnar hexagonal mesophases and/or columnar plastic phases. The unique nature of these compounds stems from their non-classical discotic structure. Although the molecules have rigid aromatic cores, they lack terminal tails and instead the polarizable atoms (S, halogens) or polar groups (CN, CO) act as unusual soft parts. On the basis of many structurally related materials, we conclude that for this type of compound molecular stacking in the solid state is a prerequisite for the appearance of a columnar mesophase, although other intermolecular interactions within the layers are also important in establishing liquid-crystalline order. The behavior reported for these mesomorphic molecules opens up new possibilities in the search for related molecular interactions that might be useful for the construction of supramolecular architectures with particular properties.     

3,3′‐Bi(1,2,4‐oxadiazoles) Featuring the Fluorodinitromethyl and Trinitromethyl Groups

Here we report on the preparation of two hydrogen atom free 3,3′‐bi(1,2,4‐oxadiazole) derivatives. 5,5′‐Bis(fluorodinitromethyl)‐3,3′‐bi(1,2,4‐oxadiazole) was synthesised by fluorination of diammonium 5,5′‐bis(dinitromethanide)‐3,3′‐bi(1,2,4‐oxadiazole). For our previously reported analogue 5,5′‐bis(trinitromethyl)‐3,3′‐bi(1,2,4‐oxadiazole), a new synthetic route starting from new 3,3′‐bi(1,2,4‐oxadiazolyl)‐5,5′‐diacetic acid was developed. In this course also hitherto unknown 5,5′‐dimethyl‐3,3′‐bi(1,2,4‐oxadiazole) was isolated. The compounds were characterised by multinuclear NMR spectroscopy, IR and Raman spectroscopy, elemental analysis as well as mass spectrometry. X‐ray diffraction studies were performed and the crystal structures for the 5,5'‐dimethyl and 5,5'‐(fluorodinitromethyl) derivatives are reported. The energetic 5,5'‐(fluorodinitromethyl) and 5,5'‐(trinitromethyl) compounds do not contain any hydrogen atoms and show remarkable high densities. Furthermore, the thermal stabilities and sensitivities were determined by differential scanning calorimetry (DSC) and standardised impact and friction tests. The heats of formation were calculated by the atomisation method based on CBS‐4M enthalpies. With these values and the room‐temperature X‐ray densities, several detonation and propulsion parameters, such as the detonation velocity and pressure as well as the specific impulse of mixtures with aluminium, were computed using the EXPLO5 code.     

Multifunctional Supramolecular Dendrimers with an s‐Triazine Ring as the Central Core: Liquid Crystalline,Fluorescence and Photoconductive Properties

Novel liquid crystal (LC) dendrimers have been synthesised by hydrogen bonding between an s‐triazine as the central core and three peripheral dendrons derived from bis(hydroxymethyl)propionic acid. Symmetric acid dendrons bearing achiral promesogenic units have been synthesised to obtain 3:1 complexes with triazine that exhibit LC properties. Asymmetric dendrons that combine the achiral promesogenic unit and an active moiety derived from coumarin or pyrene structures have been synthesised in order to obtain dendrimers with photophysical and electrochemical properties. The formation of the complexes was confirmed by IR and NMR spectroscopy data. The liquid crystalline properties were investigated by differential scanning calorimetry, polarising optical microscopy and X‐ray diffractometry. All complexes displayed mesogenic properties, which were smectic in the case of symmetric dendrons and their complexes and nematic in the case of asymmetric dendrons and their dendrimers. A supramolecular model for the lamellar mesophase, based mainly on X‐ray diffraction studies, is proposed. The electrochemical behaviour of dendritic complexes was investigated by cyclic voltammetry. The UV/Vis absorption and emission properties of the compounds and the photoconductive properties of the dendrons and dendrimers were also investigated     

Fingerprinting of bottle-grade poly(ethylene terephthalate) via matrix-assisted laser desorption/ionization mass spectrometry

Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) has been shown to provide a valuable technique to study the thermomechanical degradation of poly(ethylene terephthalate) (PET). MALDI-MS has been tested to monitor both the admixture of post-consumption bottle-grade PET (PET_pc-btg) with virgin bottle-grade PET (PET_v-btg) and the thermomechanical degradation effects on the chemical properties of PET_v-btg. Principal component analysis of MALDI-MS data classify the samples into groups with specific features: a) PET-btg with intrinsic viscosities of 0.80 or 0.65-0.60 dL g⁻¹); b) processed or virgin PET with the same intrinsic viscosity; c) PET_v-btg from PET containing PET_pc-btg; and d) PET_v-btg from different manufacturers. MALDI-MS data is therefore able to reveal the quality of PET-btg resins preventing frauds and illegal use of recycled PET-btg.