AES investigations of the iron surface composition after laser irradiation under atmospheric conditions

The laser induced modification of iron surfaces with atmospheric species was investigated by means of Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). Different laser systems were used for irradiating iron samples in a wide range of the laser processing parameters up to small foci and ultra short pulses.A nitriding of iron connected with an oxidation of the near surface region was observed in the wavelength range between 193 nm and 10.6 m using large foci (0.1 cm²) and short pulses (10...1400ns). In case of small foci (7·10^–6cm²) with ns-pulses (50 ns) an enrichment of the iron melt with nitrogen and an advanced oxidation of the surrounding area of the laser spot were detected. When using shorter pulses (200 fs, 40 ps) no indications for a nitriding were found.     

Structural analysis of Cryptosporidium parvum.

Cryptosporidium parvum (Apicomplexa, formerly Sporozoa) is the causative agent of cryptosporidiosis, an enteric disease of substantial medical and veterinary importance. C. parvum shows a number of unique features that differ from the rest of the class of coccidea in which it is currently grouped taxonomically. Differences occur in the overall structure of the transmission form and the invasive stages of the parasite, its intracellular location, the presence of recently described additional extracellular stages, the host range and target cell tropism, the ability to autoinfection, the nonresponsiveness to anticoccidial drugs, the immune response of the host, and immunochemical and genetic characteristics. These differences have an important impact on the infectivity, the epidemiology, the therapy, and the taxonomy of the parasite. The present article describes the structural analysis of the parasite using light and electron microscopy with an emphasis on structural details unique to C. parvum.     

Nachweis der Exposition gegen O,O-Dimethyl-O-(3-methyl-4-nitrophenyl)-thiophosphat durch die Bestimmung von p-Nitro-m-kresol im Harn

Zusammenfassung Die spektrophotometrische Bestimmung von p-Nitro-m-kresol bei 400 nm wurde zum Zweck eines frühzeitigen und empfindlichen Nachweises der Exposition, sowie zur Untersuchung des Metabolismus von Metation (Folithion, Sumithion) modifiziert. Nach der sauren Hydrolyse von Harn beseitigt man die Harnpigmente durch Oxydation mit H₂O₂ und durch Abtrennung von p-Nitro-m-kresolat durch Ausschütteln mit Acetonitril aus 5 n Natronlauge. Die Ausbeute der Rückgewinnung bei einer Konzentration von 0,5 ppm p-Nitro-m-kresol betrug 97,3±6,3%, bei 5 ppm 92,6±2,4%. Bei stark pigmentierten Harnen (insbesondere tierischer Herkunft) wird eine weitere Reinigung vorgenommen und zwar durch die Beseitigung der Abbauprodukte mit Oxalatpuffer aus Toluol. Die Ausbeute betrÄgt bei 0,5 ppm 86,5±5,1%, bei 5 ppm 85,2±3,1%. Die untere Bestimmungsgrenze liegt bei 1,5 g p-Nitro-m-kresol in 10 ml Harn (0,15 ppm).

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Summary The early and sensitive detection of an exposure to Metation (Folithion, Sumithion) has been performed by a modified spectrophotometric determination of p-nitro-m-cresol in the urine at 400nm. After acid hydrolysis of the urine the pigments are removed by means of oxidation with H₂O₂ and separation of p-nitro-m-cresol by extraction from 5 N NaOH solution into acetonitrile. The recovery of p-nitro-m-cresol was 97.3±6.3% and 92.6±2.4% with concentrations of 0.5 ppm and 5 ppm, respectively. Further purification is required for highly pigmented urines (especially of animal origin), viz., the removal of decomposition products by extraction from toluene solution into oxalate buffer. 86.5±5.1% and 85.2±3.1% have been recovered with concentrations of 0.5 ppm and 5 ppm, respectively. The lower limit of determination is 1.5 g of p-nitro-m-cresol in 10 ml of urine (0.15 ppm).

     

Natural Occurrence of Enantiomeric and meso-Astaxanthin. 5. Ex wild salmon (Salmo salar and Oncorhynchus)

The configurational isomers of astaxanthin (3,3′-dihydroxy-β,β-carotene-4,4′-dione) from the flesh of salmon (Salmo salar and Oncorhynchus) caught at different places in Europe and Canada were isolated and analyzed as (?)-camphanic acid diesters by means of HPLC. The biological variation in the composition of the configurational isomers in seven fish was surprisingly similar: 78 to 85% of (3S, 3′S)-astaxanthin, 12 to 17% (3R, 3′R)-astaxanthin and 2 to 6% meso-astaxanthin.     

Photopolymers for Rapid Prototyping of Soluble Mold Materials and Molding of Cellular Biomaterials

Summary. To substitute cross-linked photopolymers in rapid prototyping of mold materials and therefore extend the range of materials which can be casted, organo-soluble photopolymers were developed. Branched bisalkylacrylamides were suitable as base component for such formulations, due to their high reactivity, good mechanical properties, and excellent solubility of the formed polymers. These molding materials were used to prepare cellular biocompatible materials which could be used as bone replacement materials. Biocompatible crosslinkers based on methacrylates from hydrolyzed gelatine or lactic acid ethyleneglycol blockcopolymers and commercially available reactive diluents are the base components of such a formulation. Biocompatibility was investigated by osteoblast-like cells. Cellular biocompatible parts were obtained by thermal polymerization in soluble mould materials prepared by 3D-photoshaping.     

Verbesserte Apparatur zur Bestimmung der primären Aminogruppe

Zusammenfassung Die früher beschriebene Apparatur zur Bestimmung der primären Aminogruppe wurde verbessert. Auch die Handhabung wurde vereinfacht. Die einzelnen Teile der Apparatur (Desaminierungsteil, Absorber) können nun unabhängig voneinander ausgewaschen und luftfrei gemacht werden. Die Absorber sind für etwa 30 bis 50 Analysen benützbar, bevor sie erneuert werden müssen.

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Summary The apparatus previously described for the determination of primary amino groups has been improved. Also the manipulation is simplified. The individual segments of the apparatus (deamination part, absorber) can now be washed out independently of each other, and rendered free of air. The absorbers may be used for around 30 to 50 analyses before they must be renewed.

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Der Firma P. Haack, Wien danken wir für das besondere Entgegen-Kommen bei der Entwicklung der Apparatur.     

Zur regioselektiven nucleophilen Addition an 2,3-Dihydrobilatriene-abc

Donors are added regioselectively to position 10 of 2,3-dihydrobilatrienes-abc in a reversible reaction, which is complicated in case of strongly basic donors due to the easy deprotonation of the partially saturated ring. Compared to the bilatrienes-abc the addition equilibrium is retarded by about two orders of magnitude.

     

Spectroscopic studies of substrate interactions with clavaminate synthase 2, a multifunctional alpha-KG-dependent non-heme iron enzyme: correlation with mechanisms and reactivities

Using a single ferrous active site, clavaminate synthase 2 (CS2) activates O(2) and catalyzes the hydroxylation of deoxyguanidinoproclavaminic acid (DGPC), the oxidative ring closure of proclavaminic acid (PC), and the desaturation of dihydroclavaminic acid (and a substrate analogue, deoxyproclavaminic acid (DPC)), each coupled to the oxidative decarboxylation of cosubstrate, alpha-ketoglutarate (alpha-KG). CS2 can also catalyze an uncoupled decarboxylation of alpha-KG both in the absence and in the presence of substrate, which results in enzyme deactivation. Resting CS2/Fe(II) has a six-coordinate Fe(II) site, and alpha-KG binds to the iron in a bidentate mode. The active site becomes five-coordinate only when both substrate and alpha-KG are bound, the latter still in a bidentate mode. Absorption, CD, MCD, and VTVH MCD studies of the interaction of CS2 with DGPC, PC, and DPC provide significant molecular level insight into the structure/function correlations of this multifunctional enzyme. There are varying amounts of six-coordinate ferrous species in the substrate complexes, which correlate to the uncoupled reaction. Five-coordinate ferrous species with similar geometric and electronic structures are present for all three substrate/alpha-KG complexes. Coordinative unsaturation of the Fe(II) in the presence of both cosubstrate and substrate appears to be critical for the coupling of the oxidative decarboxylation of alpha-KG to the different substrate oxidation reactions. In addition to the substrate orientation relative to the open coordination position on the iron site, it is hypothesized that the enzyme can affect the nature of the reactivity by further regulating the binding energy of the water to the ferrous species in the enzyme/succinate/product complex.     

Saludimerines A and B, novel-type dimeric alkaloids with stereogenic centers and configurationally semistable biaryl axes

The first biarylic bis-morphinanedienone alkaloids, saludimerines A (3a) and B (3b), isolated from a tree of Croton flavens (Euphorbiaceae) are described. These naturally occurring dimers of the known alkaloid salutaridine are joined together via a rotationally hindered biaryl axis, giving rise to atropo-diastereomers that are configurationally stable at room temperature but slowly interconvert in methanolic solution within several days. Their structures were established by spectroscopic methods and by partial synthesis, which was achieved by a highly atropo-diastereoselective biomimetic oxidative coupling of the monomeric precursor, salutaridine. Their axial configurations were elucidated by circular dichroism (CD) investigations, which succeeded despite the fact that the two atropo-diastereomers exhibit near-identical CD spectra. This remarkable phenomenon was rationalized by quantum chemical CD calculations. The configurational assignment of saludimerines A (3a) as P-axial and B (3b) as M was corroborated by atropisomer-specific NOE interactions between protons of the one molecular half with nuclei in the other.