Aldehyde cruciforms: dosimeters for primary and secondary amines

We demonstrate that aldehyde-substituted donor-acceptor cruciforms [1,4-bis(arylethynyl)-2,5-distyrylbenzenes] are useful dosimeters for primary amines, primary diamines, and secondary amines. The 1,n-diamines are particularly reactive towards this dosimeter and can be detected in less than 100 ppm concentration. Using a single aldehyde-functionalized cruciform in seven different solvents allowed us to discern fourteen different amines by digital photography and statistical evaluation of the response patterns extracted as red, green, blue (RGB) values.     

Zinc-rich compounds of iron and cobalt: formation of [Fe2Zn(n)] (n = 2-4) and [Co2Zn3] cores

The reactions of heteroleptic GaCp*/CO containing transition metal complexes of iron and cobalt, namely [(CO)(3)M(μ(2)-GaCp*)(m)M(CO)(3)] (Cp* = pentamethylcyclopentadienyl; M = Fe, m = 3; M = Co, m = 2) and [Fe(CO)(4)(GaCp*)], with ZnMe(2) in toluene and the presence of a coordinating co-solvent were investigated. The reaction of the iron complex [Fe(CO)(4)(GaCp*)] with ZnMe(2) in presence of tetrahydrofurane (thf) leads to the dimeric compound [(CO)(4)Fe{μ(2)-Zn(thf)(2)}(2)Fe(CO)(4)] (1). Reaction of [(CO)(3)Fe(μ(2)-GaCp*(3))Fe(CO)(3)] with ZnMe(2) and stoichiometric amounts of thf leads to the formation of [(CO)(3)Fe{μ(2)-Zn(thf)(2)}(2)(μ(2)-ZnMe)(2)Fe(CO)(3)] (2) containing {Zn(thf)(2)} as well as ZnMe ligands. Using pyridine (py) instead of thf leads to [(CO)(3)Fe{μ(2)-Zn(py)(2)}(3)Fe(CO)(3)] (3) via replacement of all GaCp* ligands by three{Zn(py)(2)} groups. In contrast, reaction of [(CO)(3)Co(μ(2)-GaCp*)(2)Co(CO)(3)] with ZnMe(2) in the presence of py or thf leads in both cases to the formation of [(CO)(3)Co{μ(2)-ZnL(2)}(μ(2)-ZnCp*)(2)Co(CO)(3)] (L = py (4), thf (5)) via replacement of GaCp* with {Zn(L)(2)} units as well as Cp* transfer from the gallium to the zinc centre. All compounds were characterised by NMR spectroscopy, IR spectroscopy, single crystal X-ray diffraction and elemental analysis.     

Synthesis of trans‐Fused Oxabicyclo[5.2.0]nonan‐2‐ones via [2+2] Photocycloaddition of Oxepinones to Conjugated Alkenes

On irradiation (350 nm) in the presence of 2,3‐dimethylbuta‐1,3‐diene, benzoxepinone 2 and dioxepinone 3 were converted regio‐ and diastereoselectively to trans‐fused oxabicyclo[5.2.0]nonanones 5 and 9 , respectively.     

The rich chemistry of [Zn2Cp*2]: trapping three different types of zinc ligands in the PdZn7 complex [Pd(ZnCp*)4(ZnMe)2{Zn(tmeda)}

The synthesis, structural characterization, and bonding situation analysis of a novel, all-zinc, hepta-coordinated palladium complex [Pd(ZnCp*)(4)(ZnMe)(2){Zn(tmeda)}] (1) is reported. The reaction of the substitution labile d(10) metal starting complex [Pd(CH(3))(2)(tmeda)] (tmeda = N,N,N',N'-tetramethyl-ethane-1,2-diamine) with stoichiometric amounts of [Zn(2)Cp*(2)] (Cp* = pentamethylcyclopentadienyl) results in the formation of [Pd(ZnCp*)(4)(ZnMe)(2){Zn(tmeda)}] (1) in 35% yield. Compound 1 has been fully characterized by single-crystal X-ray diffraction, (1)H and (13)C NMR spectroscopy, IR spectroscopy, and liquid injection field desorption ionization mass spectrometry. It consists of an unusual [PdZn(7)] metal core and exhibits a terminal {Zn(tmeda)} unit. The bonding situation of 1 with respect to the properties of the three different types of Zn ligands Zn(R,L) (R = CH(3), Cp*; L = tmeda) bonded to the Pd center was studied by density functional theory quantum chemical calculations. The results of energy decomposition and atoms in molecules analysis clearly point out significant differences according to R vs L. While Zn(CH(3)) and ZnCp* can be viewed as 1e donor Zn(I) ligands, {Zn(tmeda)} is best described as a strong 2e Zn(0) donor ligand. Thus, the 18 valence electron complex 1 nicely fits to the family of metal-rich molecules of the general formula [M(ZnR)(a)(GaR)(b)] (a + 2b = n ≥ 8; M = Mo, Ru, Rh; Ni, Pd, Pt; R = Me, Et, Cp*).     

New method for resolving the enantiomeric composition of 2-methyltetrols in atmospheric organic aerosols

In order to facilitate the determination of the primary and secondary origin of atmospheric organic aerosols, a novel method involving chiral capillary gas chromatography coupled with mass spectrometry has been developed and validated. The method was focused on the analysis of 2-methylerythritol and 2-methylthreitol, considered to be tracers of secondary organic aerosols from the oxidation of atmospheric isoprene. The method was validated by performing various tests using authentic standards, including pure enantiomeric standards. The result showed that the analytical method itself does not affect the enantiomeric composition of the samples analyzed. The method was applied on atmospheric aerosols from a boreal forest collected in Aspvreten, Sweden and on laboratory samples obtained from liquid phase oxidation of isoprene and smog chamber experiments. Aerosol samples contained one enantiomer of 2-methylerythritol in significantly larger quantities than the others. In contrast, the liquid-phase oxidation of isoprene and its gas-phase oxidation in the smog chamber produced all enantiomers in equal quantities. The results obtained where the enantiomer fraction, EF, is larger than 0.50 suggest that 2-methyltetrols in atmospheric aerosols may also have biological origin. Information about the differences between enantiomer fractions obtained using this method brings new insights in the area of atmospheric aerosols.     

Increased fraction of low-density structures in aqueous solutions of fluoride

X-ray absorption spectroscopy (XAS) and small angle x-ray scattering (SAXS) were utilized to study the effect of fluoride (F(-)) anion in aqueous solutions. XAS spectra show that F(-) increases the number of strong H-bonds, likely between F(-) and water in the first hydration shell. SAXS data show a low-Q scattering intensity increase similar to the effect of a temperature decrease, suggesting an enhanced anomalous scattering behavior in F(-) solutions. Quantitative analysis revealed that fluoride solutions have larger correlation lengths than chloride solutions with the same cations but shorter compared to pure water. This is interpreted as an increased fraction of tetrahedral low-density structures in the solutions due to the presence of the F(-) ions, which act as nucleation centers replacing water in the H-bonding network and forming stronger H-bonds, but the presence of the cations restricts the extension of strong H-bonds.     

Enhanced small-angle scattering connected to the Widom line in simulations of supercooled water

We present extensive simulations on the TIP4P∕2005 water model showing significantly enhanced small-angle scattering (SAS) in the supercooled regime. The SAS is related to the presence of a Widom line (T(W)) characterized by maxima in thermodynamic response functions and Ornstein-Zernike correlation length. Recent experimental small-angle x-ray scattering data [Huang et al., J. Chem. Phys. 133, 134504 (2010)] are excellently reproduced, albeit with an increasing temperature offset at lower temperatures. Assuming the same origin of the SAS in experiment and model this suggests the existence of a Widom line also in real supercooled water. Simulations performed at 1000 bar show an increased abruptness of a crossover from dominating high-density (HDL) to dominating low-density (LDL) liquid and strongly enhanced SAS associated with crossing T(W), consistent with a recent determination of the critical pressure of TIP4P∕2005 at 1350 bar. Furthermore, good agreement with experimental isothermal compressibilities at 1000, 1500, and 2000 bar shows that the high pressure supercooled thermodynamic behavior of water is well described by TIP4P∕2005. Analysis of the tetrahedrality parameter Q reveals that the HDL-LDL structural transition is very sharp at 1000 bar, and that structural fluctuations become strongly coupled to density fluctuations upon approaching T(W). Furthermore, the tetrahedrality distribution becomes bimodal at ambient temperatures, an observation that possibly provides a link between HDL-LDL fluctuations and the structural bimodality in liquid water indicated by x-ray spectroscopic techniques. Computed x-ray absorption spectra are indeed found to show sensitivity to the tetrahedrality parameter.     

Studies on the chromatographic fractionation of metabolites of benzo[a]pyrene in faeces and urine from germfree and conventional rats

Rats, germfree and conventional, were dosed with 14C-labelled benzo[a]pyrene. Faeces and urine were collected. Metabolites in faeces were effectively extracted with a new method using a combination of solvents and solid sorbents. Metabolites in urine were extracted with octadecylsilane-bonded silica. The metabolites were fractionated into groups by chromatography on a cation exchanger (SP-LH-20 or SP-Sephadex C-25) and an anion exchanger (TEAP-LH-20). Some of the groups were further purified by column chromatography and analysed by HPLC and TLC. The analyses show a complex pattern of metabolism. A large part of the metabolites (9-24% depending on animal type and route of excretion) had amphoteric properties, e.g. like glutathione and cysteine conjugates. The abundance of conjugates sensitive to beta-glucuronidase and sulphatase was low. The relative amount of acidic conjugates in faeces was much higher in the germfree than in the conventional rats indicating the influence of the intestinal flora on the metabolism. The results support the view that the mercapturic acid pathway is a quantitatively important metabolic route for benzo[a]pyrene in rats. The methods of extraction and group fractionation were designed to be generally applicable to the analysis of lipophilic xenobiotics and their metabolites.     

Expression of Hepatoma-derived growth factor family members in the adult central nervous system

Background  

Hepatoma-derived growth factor (HDGF) belongs to a polypeptide family containing five additional members called HDGF related proteins 1–4 (HRP-1 to -4) and Lens epithelial derived growth factor. Whereas some family members such as HDGF and HRP-2 are expressed in a wide range of tissues, the expression of others is very restricted. HRP-1 and -4 are only expressed in testis, HRP-3 only in the nervous system. Here we investigated the expression of HDGF, HRP-2 and HRP-3 in the central nervous system of adult mice on the cellular level by immunohistochemistry. In addition we performed Western blot analysis of various brain regions as well as neuronal and glial cell cultures.