Chemoenzymatic synthesis of sialyl oligosaccharides with sialidases employing transglycosylation methodology

A series of sialyloligosaccharides was synthesized using the transglycolytic activity of the sialidases from Vibrio cholerae, Clostridium perfringens, Salmonella typhimurium, and Newcastle disease virus. According to their hydrolytic activities the sialidases from V. cholerae and C. perfringens catalyze preferentially the formation of sialyl alpha(2-6)-linkages whereas the sialidases from S.typhimurium and Newcastle disease virus show a distinct preference for alpha(2-3) directed sialylations. Using combined chemical and enzymatic methodologies structures such as T-(Thomsen-Friedenreich) antigen [beta-D-Gal-(1-3)-alpha-D-GalNAc-OThr], Tn-(Thomsen nouveau) antigen (alpha-D-GalNAc-OThr) and beta-D-Gal-(1-4)-alpha-D-2-deoxy-Gal-OMe were sialylated in alpha(2-3)- and alpha(2-6)-positions regioselectively or in high regioisomeric excess and purified by simple isolation procedures. Depending on the enzyme source and acceptor structure yields for transsialylation varied between 10 and 30%.     

Neue Verbindungen mit Granatstruktur. VI. Vanadate

New Compounds with Garnet Structure. VI. Vanadates The preparation of vanadate-garnets of the following three types is reported: (I) {Na₃}[B₂^III](V₃)O₁₂ (B^III = Cr, Sc), (II) {LiCa₂}[B₂^II](V₃)O₁₂ (B^II = Mg), (III) {Ca₂A^III}[Li₂] (V₃)O₁₂ (A^III = In, Sc). The Cr-compound of type (I) decomposes above 690°C into a mixture of Cr₂O₃ and NaVO₃. The analogous Fe-compound decomposes in a similar way already at 400°C; therefore the preparation by solid state reaction is not possible. Employing larger B^III-ions (Y, Yb, Lu) no garnets of type (I), but mixtures of B^IIIVO₄ (zircon structure) and Na₃B^IIIV₂O₈ are formed. Garnets of type (II) do not exist, when B^II are Co and Ni. Mixtures of {Ca₃}[LiB^II](V₃)O₁₂ (garnet structure), LiB^IIVO₄ (spinel structure) and B₃^II(VO₄)₂ are formed. With type (III) for A^III = Y reaction occurs forming a mixture of YVO₄, Ca₃(VO₄)₂ and Li₃VO₄.     

Einige bestrahlungsexperimente mit 2, 1-Benzisothiazolen

Some Irradiation Experiments with 2, 1-Benzisothiazoles 2, 1-Benzisothiazole ( 1 ) on irradiation with a mercury high-pressure lamp in benzene/diethylamine yields, after acetylation, 2-acetylamino-benzaldehyde ( 3 ; Scheme 1). Similarly, irradiation of 3-chloro-2, 1-benzisothiazole ( 2 ) in benzene/diethylamine leads to a mixture of 3-dimethylamino-2, 1-benzisothiazole ( 6a ) and N, N-diethyl-thioanthranilamide ( 7a ; Scheme 2). Benzisothiazole 6a , on irradiation, is not transformed into 7a . On the other hand, when 2 is irradiated in methanol a mixture of 3-methoxy-2, 1-benzisothiazole ( 4a ) and methyl anthranilate ( 5a ; Scheme 2) is obtained. In this case, 4a on irradiation in methanol or ethanol also yields 5a . No exchange of the methoxy group in 4a is observed when the irradiation is performed in ethanolic solution. Thus, 2, 1-benzisothiazoles 1 , 2 and 4a react photochemically by N,S-bond cleavage and hydrogen-atom abstraction from the solvent (Scheme 3). 3-Chloro-2, 1-benzisothiazole ( 2 ) shows a second photoreaction, i.e. nucleophilic exchange of the chloro substituent by methanol or diethyl amine. The latter reaction can also be observed thermally, e.g. in boiling methanol in the presence of methoxide ions.     

Thermodynamic properties of two metal-rich tantalum sulfides: Ta2S and Ta6S

The incongruent vaporization reactions of Ta₂S and Ta₆S have been investigated by mass-loss effusion in the temperature range 1576 to 1902 K. By extrapolation of P_S(obs) to equilibrium the enthalpies of the reactions $\text{3}\text{2}\text{Ta}{}_2\text{S(s)}\text{=}\text{1}\text{2}\text{Ta}{}_6\text{S(s) + S(g)}$ and Ta₆S = 6 Ta(s) + S(g) were found to be $\text{ΔH}{}^0{}_{298}\text{R}\text{= 53.0(0.3) · 10}{}^3\text{K}$ and $\text{ΔH}{}^0{}_{298}\text{R}\text{= 58.1(0.4) · 10}{}^3\text{K}$, respectively. Comparison between the above values, determined by a 2nd law treatment, and 3rd law values was used to derive fef (“free energy function”) values for Ta and S in the compounds. These postulated fef's, which apply only to the elements as present in the compounds measured, are compared to tabulated quantities for the pure solid elements to provide a criterion for 2nd and 3rd law evaluation.     

Cathodoluminescence Depth Profiling in SiO2:Ge Layers

 For investigation of the luminescent center profile cathodoluminescence measurements are used under variation of the primary electron energy E ₀ = 2…30 keV. Applying a constant incident power regime (E ₀·I ₀ = const), the depth profiles of luminescent centers are deduced from the range of the electron energy transfer profiles dE/dx. Thermally grown SiO₂ layers of thickness d = 500 nm have been implanted by Ge⁺-ions of energy 350 keV and doses (0.5–5)10¹⁶ ions/cm². Thus Ge profiles with a concentration maximum of (0.4 – 4) at% at the depth of d_m≅240 nm are expected. Afterwards the layers have been partially annealed up to T _a = 1100 °C for one hour in dry nitrogen. After thermal annealing, not only the typical violet luminescence (λ = 400 nm) of the Ge centers is strongly increased but also the luminescent center profiles are shifted from about 250 nm to 170 nm depth towards the surface. This process should be described by Ge diffusion processes, precipitation and finally Ge nanocluster formation. Additionally, a Ge surface layer is piled-up extending to a depth of roughly 25 nm.     

First experiments on transmutation studies of129I and237Np using relativistic protons of 3.7 GeV

First experiments on the transmutation of long-lived¹²⁹I and²³⁷Np using relativistic protons of 3.7 GeV are described. Relativistic protons generate in extended Pb-targets substancial neutron fluences. These neutrons get moderated in paraffin and are used for transmutation as follows:¹²⁹I(n,)¹³⁰I and²³⁷Np(n,)²³⁸Np. The isotopes¹³⁰I (T _1/2-12.36 h) and²³⁸Np (T _1/2=2.117 d) were identified radiochemically. One can estimate the transmutation cross-section (n,) in the given neutron field as (¹²⁹I(n,))=(10±2)b and (²³⁷Np(n,))=(140±30)b The experiments were carried out in November 1996 at the Synchrophasotron, LHE, Dubna, Russia. The investigation has been performed at the Laboratory of High Energies, JINR, Dubna.     

Eine spezifische colorimetrische Methode zur Bestimmung der Sorbins?ure

Zusammenfassung Es wird eine einfache Methode zur schnellen Bestimmung (1 Std) von Sorbinsäure in Lebensmitteln beschrieben. Die Sorbinsäure wird durch Wasserdampfdestillation verlustlos vom Lebensmittel abgetrennt und im Destillat mit saurer Kaliumdichromatlösung oxydiert. Dabei entsteht unter anderem Malondialdehyd, der mit Thiobarbitursäure einen beständigen roten Farbstoff bildet, dessen Absorptionsmaximum bei 532 nm liegt. Die rote Lösung wird colorimetriert, und über eine Eichgerade, die mit 2–10 g Sorbinsäure aufgestellt worden ist, wird der Gehalt an Sorbinsäure bestimmt. Die Methode wird durch keinen der üblichen Konservierungsstoffe gestört. Verschiedenen Lebensmitteln zugesetzte Sorbinsäuremengen wurden zu 100±2% wiedergefunden. Der qualitative Nachweis kann in vielen Lebensmitteln ohne Destillation innerhalb weniger Minuten visuell durchgeführt werden.Vorgetragen auf der 18. Arbeitstagung des Arbeitskreises Südwestdeutschland der Fachgruppe Lebensmittelchemie und gerichtliche Chemie in der Gesellschaft deutscher Chemiker in Weinheim (Bergstra\e) am 19./20. 5. 1960.Meinem Assistenten, Herrn F. Nagel, sei für die gewissenhafte Durchführung einer gro\en Zahl von Versuchen aufrichtig gedankt.Wir danken ferner der Fa. Rostock Gebrüder Friedrich Söhne, Elmshorn/Holstein, fÜr die Überlassung von Margarineproben mit Sorbinsäure und den Hoechster Farbwerken fÜr die Bereitstellung verschiedener sorbinsäurehaltiger Lebensmittel.     

Kathodenstrahlpolarographische Bestimmung von Spuren Kobalt und Zink in Nickel und Nickelsalzen

Zusammenfassung Eine Methode zur kathodenstrahlpolarographischen Bestimmung von Spuren Kobalt und Zink in Nickel und Nickelsalzen wird beschrieben. Die Spuren werden untereinander und von der Matrix über den Anionenaustauscher Dowex 1X8 getrennt. Die Nachweisgrenzen betragen für Kobalt 5·10^–4% und für Zink 4·10^–4%.

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Summary A method is described for the cathode-ray polarographic determination of cobalt and zinc traces in nickel and nickel salts after separation by the anionexchange resin Dowex 1X8. Traces are detectable as low as 5·10^–4% and 4·10^–4%, respectively.

     

Kathodenstrahlpolarographische Bestimmung von Spurenelementen in Zinnchloriden

Zusammenfassung Eine Methode wird beschrieben, die die kathodenstrahlpolarographische Bestimmung von Spuren Ni, Pb, Mn, Co, Cu, Fe, Mo in Zinnchloriden in den Bereichen 10^–4% (Ni, Pb, Mn, Cu, Fe) und 10^–5% (Mo, Co) gestattet. Über den stark basischen Anionenaustauscher AG 1×8 wird das Zinn von den Spurenelementen getrennt.

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Cathode-ray polarographic determination of trace elements in tin chlorides

A method is described for the cathode-ray polarographic detemination of traces of Ni, Pb, Mn, Co, Cu, Fe, and Mo in tin chlorides. Tin is separated from the trace metals by ion exchange on the strong basic anion-exchange resin AG 1×8. The detection limits are within the ranges of 10^–4% and 10^–5%.

     

Novel UDP-glycal derivatives as transition state analogue inhibitors of UDP-GlcNAc 2-epimerase

The "epimerisation" of UDP-GlcNAc to ManNAc, the first step in the biosynthesis of sialic acids, is catalyzed by UDP-GlcNAc 2-epimerase. In this paper we report the synthesis of transition state based inhibitors of this enzyme. To mimic the assumed first transition state of this reaction (TS 1), we designed and synthesized the novel UDP-exo-glycal derivatives 1-4. We also report herein the synthesis of 5 and 6, the first C-glycosidic derivatives of 2-acetamidoglucal, and the synthesis of the ketosides 7 and 8, which were designed as bis-substrate analogue and bis- product analogue, respectively, to mimic the second step of the reaction via the assumed second transition state TS 2.