Silver stain removal using H2O2 for enhanced peptide mass mapping by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Hydrogen peroxide solutions are reported for the removal of silver stain from proteins isolated in polyacrylamide gels. Removal of silver stain prior to in-gel digestion is shown to enhance sensitivity and sequence coverage of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) peptide mass maps. The rate of silver removal using H2O2 is influenced by H2O2 concentration and increases with increasing pH. The presence of complexation reagents such as ammonia from mass spectrometry compatible ammonium bicarbonate solutions enhances the efficiency and speed of H2O2-mediated silver removal. H2O2-mediated silver removal using the described procedure does not appear to have any detrimental effects on proteins but is observed to produce a slightly elevated level of methionine oxidization over that usually observed in in-gel tryptic digestion.     

Complexity in Complex Analysis

We show that the classical kernel and domain functions associated to an n-connected domain in the plane are all given by rational combinations of three or fewer holomorphic functions of one complex variable. We characterize those domains for which the classical functions are given by rational combinations of only two or fewer functions of one complex variable. Such domains turn out to have the property that their classical domain functions all extend to be meromorphic functions on a compact Riemann surface, and this condition will be shown to be equivalent to the condition that an Ahlfors map and its derivative are algebraically dependent. We also show how many of these results can be generalized to finite Riemann surfaces.     

The generic condition is generic

We consider the generic condition for vectors—both null and non-null—at a fixed pointp of a spacetime, and ask just how generic this condition is. In a general spacetime, if the curvature is not zero at the pointp, then the generic condition is found to be generic in the mathematical sense that it holds on an open dense set of vectors atp; more specifically, if there are as many as five non-null vectors in general position atp which fail to satisfy the generic condition, then the curvature vanishes atp. If the Riemann tensor is restricted to special forms, then stronger statements hold: An Einstein spacetime with three linearly independent nongeneric timelike vectors atp is flat atp. A Petrov type D spacetime may not have any nongeneric timelike vectors except possibly those lying in the plane of the two principal null directions; if any of the non-null vectors in such a plane are nongeneric, then so are all the vectors of that plane, as well as the plane orthogonal to it.     

Coupling routes to hexafluoro-1,3-butadiene, substituted-1,3-fluorine-containing butadienes and fluorinated polyenes

Hexafluoro-1,3-butadiene was readily prepared via a variety of self-coupling processes, such as Cu(0) mediated self-coupling of iodotrifluoroethene, Pd(0) catalyzed coupling of iodotrifluoroethene with the trifluorovinylzinc reagent, and CuBr₂ mediated coupling of the trifluorovinylzinc reagent. Perfluoro-2,3-dimethyl-1,3-butadiene was readily synthesized by the reaction of pentafluoropropenyl-2-zinc reagent with either CuBr₂ or FeCl₃. Alternatively, perfluoro-2,3-dimethyl-1,3-butadiene was prepared by oxidation of the pentafluoropropenyl-2-copper reagent with dioxygen. Cu(0) mediated coupling of an (E)-substituted ,β-difluoro-β-iodostyrene provided the first useful route to a (Z)(Z)-1,4-diaryl-1,3-tetrafluorobutadiene. Extension of the Cu(0) mediated coupling methodology to a perfluorodienyl iodide demonstrated a useful stereospecific route to perfluoropolyenes.     

Microwave-assisted highly diastereoselective synthesis of oxazolidines derived from ketones and aminoalcohols

A number of oxazolidines derived from ketones and aminoalcohols have been prepared in excellent yields using microwave irradiation. In most cases, conventional reflux failed to provide any of the desired products.     

Speciation of organotin compounds in water by gas chromatography/atomic absorption spectrometry

Summary A reproducible and interference-free method is presented for simultaneous determination of individual tri-, di- and monoalkyltin species present in aqueous systems. The ionic methyltin and butyltin compounds are extracted from water into pentane as diethyldithiocarbamate complexes at pH 5. The organic phase is then evaporated to dryness under reduced pressure, after which derivatization withn-pentyl (Pe) Grignard reagent is carried out in a microvolume ofn-octane to form pentylated alkyltin compounds R _n SnPe_(4-n) (R = Methyl, Me or Butyl, Bu). The quantitation is subsequently performed by gas chromatography with quartz furnace atomic absorption spectrometric detection (GC-AAS). Absolute detection limits range between 0.16 ng and 0.40 ng Sn for the various organotin species, allowing speciation in natural water down to the 4-10 ng 1^–1 level.

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Speziation von organischen Zinnverbindungen in Wasser durch GC/AAS

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Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

The reactions of alkoxy radicals with O2. II. n-C3H7O radicals

n-C₃H₇ONO was photolyzed with 366 nm radiation at ?26, ?3, 23, 55, 88, and 120°C in a static system in the presence of NO, O₂, and N₂. The quantum yields of C₂H₅CHO, C₂H₅ONO, and CH₃CHO were measured as a function of reaction conditions. The primary photochemical act is and it proceeds with a quantum yield ?₁ = 0.38 ± 0.04 independent of temperature. The n-C₃H₇O radicals can react with NO by two routes The n-C₃H₇O radical can decompose via or react with O₂ via Values of k₄/k₂ ? k_4b/k₂ were determined to be (2.0 ± 0.2) × 10¹⁴, (3.1 ± 0.6) × 10¹⁴, and (1.4 ± 0.1) × 10¹⁵ molec/cm³ at 55, 88, and 120°C, respectively, at 150-torr total pressure of N₂. Values of k₆/k₂ were determined from ?26 to 88°C. They fit the Arrhenius expression: For k₂ ? 4.4 × 10^?11 cm³/s, k₆ becomes (2.9 ± 1.7) × 10^?13 exp{?(879 ± 117)/T} cm³/s. The reaction scheme also provides k_4b/k₆ = 1.58 × 10¹⁸ molec/cm³ at 120°C and k_8a/k₈ = 0.56 ± 0.24 independent of temperature, where