New polyazaheterocycles. 9-Methyl-di-s-triazolo[4,3-a:4,3-c]pyrimidine and 9-methyl-s-triazolo[4,3-c]tetrazolo[1,5-a]pyrimidine

9-Methyl-di-s-triazolo[4,3-a:4,3-c]pyrimidine and 9-methyl-s-triazolo[4,3-c]tetrazolo[1,5-a]pyrimidine have been synthetized from 4-hydrazino-7-methyl-s-triazolo[4,3-c]pyrimidine. Structural assignments based on nmr, ir and chemical manipulations are discussed.     

Simultaneous Determination of Trichothecenes A, B, and D in Maize Food Products by LC–MS–MS

Two new methods of analysis, based on liquid chromatography–tandem mass spectrometry, for simultaneous determination of trichothecenes A, B, and D in maize flour and oil have been developed and validated in accordance with European Commission decision 2002/657/EC (recovery, CCα, CCβ, and precision). The trichothecenes were extracted from maize flour by matrix solid-phase dispersion, with recoveries ≥79%, and from maize oil by liquid–liquid extraction, with recoveries ≥78%. Limits of quantitation ranged between 0.03 and 50 μg kg^?1, depending on the electrospray response to each analyte and on the matrix. Monitoring of flour and oil samples with this HPLC–MS–MS method revealed the presence of deoxynivalenol, T-2 toxin, and diacetoxyscirpenol at very low concentrations.     

Simultaneous determination of the urinary metabolites of benzene, toluene, xylene and styrene using high-performance liquid chromatography/hybrid quadrupole time-of-flight mass spectrometry

A simple and rapid method using reversed-phase liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the simultaneous determination of the urinary metabolites of benzene, toluene, xylene and styrene in human urine specimens and standard solutions is described. A hybrid quadrupole/time-of-flight (QqTOF) mass spectrometer was compared for the determination of metabolite of aromatic solvents in urine samples. The metabolites selected were: trans,trans-muconic acid, hippuric acid, o-, m- and p-methylhippuric acid and phenylglyoxylic acid. The compounds were well separated from each other on narrow-bore 1-mm i.d. reversed-phase LC C-18 columns. Average recoveries for loading 100 microL of urine samples varied from 88-110% and the quantification limits were less than 30 ng/mL for each analyte (3 ng/mL for trans,trans-muconic acid). The qualitative information obtained (mass accuracy, resolution and full-scan spectra) with the QqTOF mass spectrometer allows a secure identification of analytes in biological matrices.     

Regioselective homogeneous hydrogenation of heteroaromatic nitrogen compounds by use of [RuH(CO)(NCMe)2(PPh3)2]BF4 as the precatalyst

Summary The complex [RuH(CO)(NCMe)₂(PPh₃)₂]BF₄ (1) is an efficient and regioselective catalyst precursor for the hydrogenation of polyaromatic nitrogen compounds such as quinoline (Q), isoquinoline (iQ), indole (ln), 5,6- and 7,8-benzoquinoline (BQ) and acridine (A) under relatively mild reaction conditions (125 °C, 4 atm H₂). The order of individual initial rates was: A > Q > 5,6-BQ > 7,8-BQ > ln > iQ, reflecting both steric and electronic effects. For the regioselective homogeneous hydrogenation of A to 9,10-dihydroacridine (DHA) catalysed by complex (1), a kinetic study was carried out; the experimentally determined rate law was r = k ₁ [Ru] [H₂]. These findings are consistent with a mechanism involving the hydrogenation of [RuH(CO)(A)(NCMe)(PPh₃)₂]BF₄ to yield DHA and the unsaturated species [RuH(CO)(NCMe)(PPh₃)₂]BF₄ in the rate-determining step.     

Isostructural self-assembled monolayers. 2. Methyl 1-(3-mercaptopropyl)-oligo(ethylene oxide)s

The structural order and ordering conditions of the self-assembled monolayers (SAMs) of HSCH2CH2CH2O(EO)xCH3, where EO = CH2CH2O and x = 3-9, on polycrystalline gold (Au) were determined by reflection-absorption infrared spectroscopy (RAIRS), spectroscopic ellipsometry (SE), and electrochemical impedance spectroscopy. For x = 5-7, RAIRS and SE data show that the oligo(ethylene oxide) [OEO] segments adopt the near single phase, 7/2 helical conformation of the folded-chain crystal polymorph of crystalline poly(ethylene oxide), oriented normal to the substrate. These SAMs exhibit OEO segment structure and orientation identical to that found in a previous isostructural series [HS(CH2CH2O)6-8C18H37 SAMs. Vanderah, D. J., et al. Langmuir 2003, 19, 3752] and are anisotropic films for surface science metrology where structure is constant and thickness increases in 0.30 nm increments. In addition, this is the first example of OEO SAMs to attain this highly ordered, helical conformation where the (EO)x segment is separated from the Au-sulfur headgroup by a polymethylene chain. For x = 4, 8, and 9, the SAMs are largely helical but show evidence of nonhelical conformations and establish the upper and lower limits of the isostructural set. For x = 3, the SAMs are largely disordered containing some all-trans conformation. SAM order as a function of immersion time from 100% water and 95% ethanol indicates that the HSCH2CH2CH2O(EO)5-7CH3 SAMs order faster and under a wider range of conditions than omega-alkyl 1-thiaolio(ethylene oxide) [HS(EO)xCH3] SAMs, reported earlier (Vanderah, D. J., et al. Langmuir 2002, 18, 4674 and Vanderah, D. J., et al. Langmuir 2003, 19, 2612).     

Evaluation of thermodynamic properties of irreversible protein thermal unfolding measured by DSC

Summary We assessed the applicability of the extrapolation procedure at infinite scanning rate to differential scanning calorimetry (DSC) data related to irreversible protein unfolding. To this aim, an array of DSC curves have been simulated on the basis of the Lumry-Eyring model N↔U→F. The results obtained confirmed that when the apparent equilibrium constant K_{app (T=T1/2)} is lower than 3, the application of the extrapolation procedure provides accurate thermodynamic parameters. Although this procedure applies only to monomeric proteins for which the Lumry-Eyring model is a reasonable approximation, it will hopefully contribute to increase the potential of DSC in obtaining reliable thermodynamic information regarding the folding/unfolding equilibrium.     

The Elusive beta-unsubstituted calix[5]pyrrole finally captured

[reaction: see text] The meso-decamethyl-calix[5]pyrrole 2b was synthesized from the furan-based analogue 1b via the homologation of the furan rings to pyrrole, and its solid-state structure was determined by X-ray crystallography: surprisingly, the binding constant of 2b toward chloride is found to be lower than that of the tetrameric analogue 2a.     

Thermal analysis of a drug-polymeric excipient solid system

Differential scanning calorimetry has been applied to the study of the solid system cross-linked polyvinylpyrrolidone/trimethoprim.Different results have been systematically obtained on co-ground and not co-ground mixtures, suggesting some type of interaction to take place between components as a consequence of co-grinding.A simple phenomenological model of the interaction is proposed, which quite satisfactorily agrees with thermal data.

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Zusammenfassung Das feste System von vernetztem Polyvinyl-pyrolidin/Trimethoprim wurde mittels DSC untersucht. Unterschiedliche Ergebnisse wurden systematisch für zusammen und nicht zusammen verriebene Mischungen gefunden, was auf eine Wechselwirkung zwischen Komponenten beim Verreiben hindeutet. Ein einfaches phänomenologisches Modell dieser Wechselwirkung wird vorgeschlagen, das mit thermischen Daten befriedigend übereinstimmt.

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This work has been partially supported by Ministero Pubblica Istruzione (Fondi 60%).     

Designing generalized statistical ensembles for numerical simulations of biopolymers

Conformational properties of polymers, such as average dihedral angles or molecular alpha-helicity, display a rather weak dependence on the detailed arrangement of the elementary constituents (atoms). We propose a computer simulation method to explore the polymer phase space using a variant of the standard multicanonical method, in which the density of states associated to suitably chosen configurational variables is considered in place of the standard energy density of states. This configurational density of states is used in the Metropolis acceptance/rejection test when configurations are generated with the help of a hybrid Monte Carlo algorithm. The resulting configurational probability distribution is then modulated by exponential factors derived from the general principle of the maximal constrained entropy by requiring that certain average configurational quantities take preassigned (possibly temperature dependent) values. Thermal averages of other configurational quantities can be computed by using the probability distributions obtained in this way. Moments of the energy distribution require an extra canonical sampling of the system phase space at the desired temperature, in order to locally thermalize the configurational degrees of freedom. As an application of these ideas we present the study of the structural properties of two simple models: a bead-and-spring model of polyethylene with independent hindered torsions and an all-atom model of alanine and glycine oligomers with 12 amino acids in vacuum.     

High levels of soluble herpes virus entry mediator in sera of patients with allergic and autoimmune diseases

Herpes virus entry mediator (HVEM) is a newly discovered member of the tumor necrosis factor receptor (TNFR) superfamily that has a role in herpes simplex virus entry, in T cell activation and in tumor immunity. We generated mAb against HVEM and detected soluble HVEM (SHVEM) in the sera of patients with various autoimmune diseases. HVEM was constitutively expressed on CD4(+) and CD8(+) T cells, CD19(+) B cells, CD14(+) monocytes, neutrophils and dendritic cells. In three-way MLR, mAb 122 and 139 were agonists and mAb 108 had blocking activity. An ELISA was developed to detect sHVEM in patient sera. sHVEM levels were elevated in sera of patients with allergic asthma, atopic dermatitis and rheumatoid arthritis. The mAbs discussed here may be useful for studies of the role of HVEM in immune responses. Detection of soluble HVEM might have diagnostic and prognostic value in certain immunological disorders.