Detection of traces of oxidized and reduced sulfur compounds in small samples by combination of different high-performance liquid chromatography methods

Depending on the sulfur species, picomoles of different inorganic sulfur compounds can be detected and separated by HPLC in one arrangement in a sample volume less than 50 μl. The combination of fluorescence labelling of reduced inorganic sulfur compounds such as sulfide (S²⁻), sulfite(SO₃²⁻ and thiosulfate (S₂O₃²⁻) with monobromobimane followed by an extraction of elemental sulfur (S°) by chloroform treatment enables the detection of all mentioned sulfur compounds as well as sulfate (remaining aqueous phase) in the same sample. While the derivatized sulfur compounds could be detected by their fluorescence emission at 480 nm, elemental sulfur is identified by its UV absorption at 263 nm. Sulfate in the remaining aqueous phase is detected by HPLC with indirect UV detection at 254 nm. Detection ranges for the different sulfur compounds examined are as follows: sulfide (5 μM to 1.5 mM), sulfite (5 μM to 1.0 mM), thiosulfate (1 μM to 1.5 mM), elemental sulfur (2 μM to 32 mM) and sulfate (5 μM to >1 mM).     

Electrospray-Ionization Mass Spectrometry: Detection of a radical cation present in solution: New results on the chemistry of (tetrahydropteridinone)-metal complexes

This paper marks the first reported detection of radical cations by Electrospray-Ionization Mass Spectrometry (ESI-MS). Electron Spin Resonance (ESR) measurements have proven that the detected radical cation existed already in solution and has not been generated by the electrospray ionization technique. However, we observed that the radical cation can be generated by changes in the ionization conditions. A molar mixture of 2-amino-5,6,7,8-tetrahydro-5-methylpterin-4(4H)-one dihydrochloride ( = 5,6,7,8-tetrahydro-N(5)-methylpterin-2 HCl, N(5)-MTHP-2 HCl), and tris(pentane-2,4-dionato)iron(III) in MeCN at pH 2–3 leads to the formation of a [bis(pentane-2,4-dionato)(2-amino-5,6,7,8-tetrahydro-5-methylpteridin-4 (4H)-one)]iron complex ( = [bis(pentane-2,4-dionato) (5,6,7,8-tetrahydro-N(5)-methylpteridin)]iron complex) which can be detected by ESI-MS. The results suggest that this complex might be an Fe^II radical cation, which could possibly be a suitable model complex for the active center of the phenylalanine hydroxylase. In the same solution, the stable radical cation of N(5)-MTHP is identified by ESI-MS and ESR.     

Synthesis of 3-Deaza-2′-deoxyadenosine and 3-Deaza-2′,3′-dideoxyadenosine: Glycosylation of the 4-Chloroimidazo[4,5-c]pyridinyl Anion

The convergent syntheses of 3-deazapurine 2′-deoxy-β-D -ribonucleosides and 2′,3′-dideoxy-D -ribonucleosides, including 3-deaza-2′-deoxyadenosine ( 1a ) and 3-deaza-2′,3′-dideoxyadenosine ( 1b ) is described. The 4-chloro-lH-imidazo[4,5-c]pyridinyl anion derived from 5 was reacted with either 2′-deoxyhalogenose 6 or 2′,3′-dideoxyhalogenose 10 yielding two regioisomeric (N¹ and N³) glycosylation products. They were deprotected and converted into 4-substituted imidazo[4,5-c]pyridine 2′-deoxy-β-D -ribonucleosides and 2′,3′-dideoxy-D -ribonucleosides. Compounds 1a and 1b proved to be more stable against proton-catalyzed N-glycosylic bond hydrolysis than the parent purine nucleosides and were not deaminated by adenosine deaminase.     

Norrish Type I Cleavage of Aliphatic Carboxylic Acids and Esters in Solution. A CIDNP.-study

UV.-irradiation of pivalic and isobutyric acid and their methyl esters as well as of α-hydroxy isobutyric and malonic acid in solution lead to chemically induced dynamic nuclear polarization (CIDNP.) of parent compounds and of various reaction products. CIDNP.-effects and product distributions confirm α-cleavage of the C(α), CO bond to be the major mode of photodecomposition. Scavenger experiments indicate that decomposition of the molecules from a triplet excited state is roughly equally or more probable than from a singlet excited state. Quantum yields of educt disappearance are also given for the methyl esters of pivalic and isobutyric acid.     

Über die optimale Beleuchtung einer geraden Straße

The following problem is due toL. Fejes Tóth: For a given sort of lamps letf(x) be the intensity of brightness in each point having distancex from the foot of the lamp. How must infinitely many lamps of this kind be arranged on a both-side infinite rectilinear road, such that the infimum of the intensities of brightness, extended over the whole street, is maximal, subject to the condition that the average number of lamps per kilometer is bounded by a fixed number (“Best distributions”)? The main result of this paper is: Iff is strictly convex, the equidistant distribution is best.     

Untersuchung pharmazeutischer Pr?parate

Ohne Zusammenfassung     

Heilmittelchemische Mikronachweise und -bestimmungen

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