Glycoconjugate libraries accessed by multicomponent reactions

Glycobiology opens a wide field for new therapeutic approaches. However, the complexity and unavailability of various carbohydrate test compounds has excluded this class of natural products from modern screening systems. Alternatively, glycomimetics are considered to be more drug-like candidates for development. By means of multicomponent condensations (MCCs) utilizing suitable carbohydrate synthons, rapid and effective access to glycoconjugate libraries can be obtained. The flexibility of MCCs allows the assembly of diverse carbohydrate containing libraries. It may be assumed that MCCs containing carbohydrate moieties will play an important role in glycomimetic chemistry and biology.     

A simple and versatile method for the synthesis of acetals from aldehydes and ketones using bismuth triflate

Acetals are obtained in good yields by treatment of aldehydes and ketones with trialkyl orthoformate and the corresponding alcohol in the presence of 0.1 mol % Bi(OTf)3.4H2O. A simple procedure for the formation of acetals of diaryl ketones has also been developed. The conversion of carbonyl compounds to the corresponding 1,3-dioxolane using ethylene glycol is also catalyzed by Bi(OTf)3.4H2O (1 mol %). Two methods, both of which avoid the use of benzene, have been developed.     

Novel diode laser-compatible fluorophores and their application to single molecule detection, protein labeling and fluorescence resonance energy transfer immunoassay

We describe a series of new long-wave absorbing and fluorescing cyanine dyes and labels (based on a general logic for the design of such dyes), their spectra, covalent and noncovalent linkage to proteins, their use in single molecule detection (SMD) and as donors and acceptors, respectively, in fluorescence resonance energy transfer studies. The new labels represent water-soluble and reactive fluorophores whose quantum yields increase substantially if noncovalently or covalently bound to proteins. Due to their strong absorptions between 550 and 700 nm they are excitable by light-emitting diodes or diode lasers. Their high absorbances (epsilon around 100,000) and adequate fluorescence quantum yields (phi up to 0.68 if bound to proteins) along with their availability as reactive NHS esters make them viable labels for proteins and oligomers, e.g. in context with SMD or fluorescence energy transfer immunoassay which is demonstrated for the system HSA/anti-HSA.     

On the abstract theory of additive and multiplicative Schwarz algorithms

Summary. In recent years, it has been shown that many modern iterative algorithms (multigrid schemes, multilevel preconditioners, domain decomposition methods etc.) for solving problems resulting from the discretization of PDEs can be interpreted as additive (Jacobi-like) or multiplicative (Gauss-Seidel-like) subspace correction methods. The key to their analysis is the study of certain metric properties of the underlying splitting of the discretization space into a sum of subspaces and the splitting of the variational problem on into auxiliary problems on these subspaces. In this paper, we propose a modification of the abstract convergence theory of the additive and multiplicative Schwarz methods, that makes the relation to traditional iteration methods more explicit. The analysis of the additive and multiplicative Schwarz iterations can be carried out in almost the same spirit as in the traditional block-matrix situation, making convergence proofs of multilevel and domain decomposition methods clearer, or, at least, more classical. In addition, we present a new bound for the convergence rate of the appropriately scaled multiplicative Schwarz method directly in terms of the condition number of the corresponding additive Schwarz operator. These results may be viewed as an appendix to the recent surveys [X], [Ys]. Received February 1, 1994 / Revised version received August 1, 1994     

Kryoskopische Reinheitsbestimmung kleiner Substanzmengen nach der Methode der konstantgesteuerten aufgepr?gten W?rmerate

Zusammenfassung Zur Reinheitsbestimmung schmelzbarer, vorwiegend organischer Proben wurde eine kryoskopische Apparatur nachSmit gebaut. Sie arbeitet oberhalb 99 Mol-% im Halbmikrobereich, wobei der Absolutwert der Reinheit auf ±0,05 Mol-% genau meßbar ist. Die Probe, die ständig unter strömendem Stickstoff gehalten wird, umgibt als dünne Schicht ein Platin-Widerstandsthermometer, das sich in der Mitte eines elektrisch geheizten Aluminiumzylinders befindet. Konstanz der Wärmezufuhr wird gesichert durch Regelung der Temperaturdifferenz gegen ein gleichartiges zweites Thermometer, das dicht am geheizten Zylindermantel eingesteckt ist. Die Thermometer brauchen nicht geeicht zu werden. Die Regelung wird durch eine Doppel-Wheatstonebrücke vermittelt, deren einer Ausgang auf den Schreiber und deren anderer auf die Heizung wirkt. Die graphische Auswertung ist aus dem Zweiphasen-Diagramm fest-flüssig abgeleitet. Als Bezugsstandard ist eine zweite Probe zu messen, die man durch Verunreinigung der ursprünglichen Substanz um einen bekannten Betrag erhält.

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Summary A cryoscopic apparatus for the purity assay of fusible, mostly organic samples was built afterSmit. It works in the half-micro scale above 99 mole%, where the absolute value of the purity will lie within ±0.05 mole%. The sample, which is always kept under streaming nitrogen, surrounds as a thin layer a platinum resistance thermometer that stands in the center of an electrically heated aluminium cylinder. A constant supply of heat is ensured by controlling the temperature difference against a second thermometer of the same kind, which is inserted near the heated periphery of the cylinder. It is not necessary to calibrate the thermometers. Control is mediated by a double Wheatstone bridge, the one output of which acts on the recording device, the other on the heater. The graphical evaluation of the records derives from the two-phase diagram solid-liquid. As a referential instance, a second sample has to be measured, which is obtained from the specimen through artificial contamination by a known amount.

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Unter Mitarbeit von F.Weigand und R.Baumgart.

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Herrn Dr.Ebinger, AEG-Meßgerätefabrik Berlin-Reinickendorf und Herrn Dipl.-Ing. Lutz, AEG-Büro Mannheim, habe ich für ihre große Bereitwilligkeit zu danken, mit der sie auf die Wünsche zur Bauart der Brücke eingingen. — Für Anregungen danke ich Herrn Dr.Kienitz.     

Untersuchungen zur Physisorption und Chemisorption von Wasser auf Zinkoxid-Oberflächen

The investigation of different zinc oxide samples by means of thermogravimetry and infrared spectroscopy has shown that the surface of the samples is covered by an approximately monoatomic layer of hydroxide groups. Furthermore, varying amounts of carbonate groups are found which are due to the presence of zinc hydroxide carbonate II [Zn₅(OH)₆(CO₃)₂]. Below relative water vapour pressures of p/p₀ = 0.2 (25°C), two hydrogen bridges connect one physisorbed water molecule with two chemisorbed surface hydroxide groups. In addition, about the same amount of water is physically adsorbed between vapour pressures of p/p₀ 0.2 and 0.8. At still higher relative humidity, a multimolecular layer is built up which reaches a thickness of about 200 water molecules at p/p₀ = 1.0. All samples show in the v-OH region of the IR. spectrum a broad absorption with four bands, A, B, C, and D. The position of the bands and the change of their intensities when rising the temperature of the samples up to 600°C indicate that both bands of longer wave lengths, C and D, arise from physically adsorbed water molecules, while the bands A and B are due to hydroxide groups located on the crystallographic faces (0001) and (0001 ), respectively.     

Thermal reduction and reoxidation of spinel-type Cu1−xZnxAl2O4

The thermochemical reactivity of the spinel-type quaternary metal oxide Cu_1–xZn_xAl₂O₄ has been investigated for different Cu:Zn ratios. In oxygen or inert gas atmospheres no considerable reduction is observed. In molecular hydrogen metal selective reduction of the Cu is found at relatively high temperature. The solid reduction product is made up of sintered, poorly dispersed metallic copper on a Zn-Al-O metal oxide support, a potential catalyst for the methanol synthesis. Owing to the measured high reduction temperature leading to the mentioned sintering of the metallic copper, the activity of this system cannot be high.Financial support by the Swiss National Science Foundation under project Nr. 2027933.89 is gratefully acknowledged.     

Fourier series and the conjugate function in the classes ϕ(L)

Обозначим через ? (L) кл асс всех ?-интегрируе мых 2π-периодических функ ций. При ограничении?(L)?L ¹ устанавливаются необходимые и достат очные условия, которым долж на удовлетворять?(t), что бы для каждой функцииf(x)ε ?(L) а) тригонометрически й ряд Фурье сходился в метрике ?, в) (С, а) средние ряда Фур ье сходились в метрик е ? для некоторого α > 0, с) сопряженная функци я \(\tilde f(x)\) также принадлежал а классу?(L).     

1H-NMR-spektroskopische Analyse von 2-Chlor-1.3.2-dioxarsolan

The¹H-NMR-spectral data of 2-chloro-1.3.2-dioxarsolane are presented and discussed. The protons of the methylene groups form in concentrated solutions by rapide chlorine exchange anAAAA spin system. In dilute solutions the protons form anAABB spin system, which is changed to anAAAA system by addition of chlorine ions.The vicinal H–C–C–H-coupling constants indicate a twist-envelope conformation.

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