Non-radioactive determination of PTH and dabsyl phosphoamino acids by capillary electrophoresis

Summary Capillary electrophoresis is a novel technique in the non-radioactive determination of phosphoamino acids. The main advantage of the method presented is the high selectivity and the ability to separate all phosphoamino acid derivatives. Non-radioactive determination of PTH or dabsyl phosphoamino acids by capillary electrophoresis provides a fast and simple screening procedure for all O-phosphorylated amino acids in protein and peptides in the low picomolar range.     

Synthetic reactions catalyzed by immobilized lipase from oilseed rape (Brassica napus L.)

Lipase from rape (Brassica napus L., immobilized onto celite, catalyzes esterification and transesterification reactions in hexane. The activity of the lipase is stimulated up to 35 fold by the addition of water (1.3% w/v). The activity of the lipase in hydrolysis is about 8 times higher than in the esterification reactions in hexane. Interesteri-fication reactions between mono- and diacylglycerols and transesterification reactions of mono- and diacylglycerols with alcohols were also catalyzed at relatively high rates but transesterification/esterification of these acylglycerols with fatty acids was comparatively slow. In transesterification reactions, triacylglycerols reacted rather slowly.     

Übergangsformen zwischen Einkristall- und Sphärolithwachstum im Polyäthylen

Zusammenfassung Steigert man für das Poly?thylen die Kristallisationstemperatur, so findet man Kristallformen in der folgenden Reihenfolge: rautenf?rmige Einkristalle— rautenf?rmige Einkristalle mit abgeschnittenen spitzen Ecken (“truncated lozenge crystals”)-l?ngliche sechseckf?rmige Einkristalle, bei denen die kristallographische b-Achse der orthorhombischen Elementarzelle in Richtung der l?ngsten Ausdehnung des Kristalls liegt. Diese l?nglichen Sechsecke lagern sich zu Sph?rolithen zusammen, und zwar so, da? die kristallographische b-Achse radial liegt, wie es auch bei den aus der Schmelze gewachsenen Sph?rolithen der Fall ist. Damit sind für das Poly?thylen übergangsformen zwischen den Einkristallen und Sph?rolithen aufgezeigt. Sph?rolithe, die aus der L?sung gewachsen sind, zeigen im Polarisationsmikroskop nur dann ein konzentrisches Ringsystem, wenn bei der Bildung der Sph?rolithe ein Mindestangebot an Substanz vorhanden ist. Die Ringbreite nimmt dann mit steigender Kristallisationstemperatur zu. Bei aus der Schmelze gewachsenen Poly?thylen-Sph?rolithen ist mit der Bildung von nicht-kristallographischen Verzweigungen eine Drehung der Indikatrix verbunden. Vermutlich wird also auch bei aus der L?sung gewachsenen Sph?rolithen das Ringsystem auf dem Auftreten von Verzweigungen infolge hohen Angebotes von kristallisierender Substanz beruhen.

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Summary With increasing temperature of crystallization polyethylene crystallizes from solution as lozenge single crystals, truncated lozenge crystals and longish hexagonal crystals, with the crystallographic b-axis along the long diagonal. In the solutions longish hexagonal crystal plates are able to cluster and to form spherulites, in which their crystallographic b-axes are oriented radially like the b-axes in spherulites grown from the melt. Various transition species have been observed. In polarised light the spherulites grown from solution show a concentric ring-system only, if during the crystallization a sufficient quantity of polyethylene is present. The ring-width increases with increasing crystallization temperature. Further it is shown that in polyethylene spherulites grown from the melt the rotation of the indicatrix is connected with a non-crystallographic branching. We suppose, that also for the solution-grown spherulites the ring-system depends on branching.

     

High-Yield Syntheses of Tetra-O-benzyl-α-D-glucopyranosyl bromide and Tetra-O-pivaloyl-α-D-glucopyranosyl bromide and their Advantage in the Koenigs-Knorr Reaction

Several improved approaches for the preparation of tetra-O-benzyl-α-D-glucopyranosyl bromide and tetra-O-pivaloyl-α-D-glucopyranosyl bromide are discussed. The importance of these compounds, which are useful glycosyl donors, was demonstrated by successful preparation of cholesteryl glucopyranosides in an almost neutral medium without the formation of orthoesters. In addition, accurate ¹H and ¹³C NMR resonance assignments of the synthesized cholesteryl glycosides were performed by 2D NMR spectroscopy.     

Morphologische Strukturen des Poly-3,3-bis(chloromethyl)-oxirans

Zusammenfassung Poly-3,3-bis(chloromethyl)-oxiran kristallisiert aus der Schmelze in Form von Sph?rolithen mit „blumenblattartiger“ Struktur. Das für Sph?rolithe typische Ausl?schungskreuz ist nicht immer klar ausgebildet. Aus einer übers?ttigten Xyloll?sung kristallisiert die Substanz als rautenf?rmige Einkristalle. Mit der Annahme, da\ die Molekelketten wie beim Poly?thylen senkrecht zur Rautengrundfl?che stehen und regelm?\ig gefaltet sind, folgt aus dem Elektronenbeugungsbild dieser Einkristalle eine orthorhombische Elementarzelle mit den folgenden Abmessungen:a=17,85 ?,b=8,16 ? (c=4,8 ?, aus der Literatur bekannt).

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Summary Poly-3,3-bis(chloromethyl)oxacyclobutane crystallizes from the melt as “petal-shaped” spherulites. The extinction cross, typical for spherulites, is not well developed in all cases. From a solution of xylene the substance crystallizes in the form of flat lozenges. We assume, that the molecules are perpendicular to the plane of the crystals and that they are regularly folded as in the case of polyethylene. Therewith and from the electron diffraction pattern we found the unit cell to be orthorhombic with the dimensions:a=17,85 ?,b=8,16 ? (c=4,8 ?, from literature).

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Herrn Prof. Dr.K.-H. Hellwege und Herrn Dr. W.Knappe danke ich für die Anregung zu dieser Arbeit, Herrn Dr.U. Johnsen für viele f?rdernde Diskussionen, sowie Herrn Dipl.-Phys.D. Kockott für die Ausführung derDebye-Scherrer-Aufnahmen.     

Current-induced coupling between conductance channels in membranes

The driven system of conducting channels in a nerve membrane is investigated. A current flow generates a coupling between the channels: the current through a channel is influenced by the presence of other conducting channels via the deformation of the equipotential surfaces within the media adjacent to the membrane. We derive an integral equation for the membrane voltageV(s) (s in the membrane plane) and solve it for different membrane conductance distributions(s) including models for stochastic distributions of conducting channels.V(s) is a nonlinear functional of(s). The system of coupled channels is compared with an Ising model. The system exhibits a multi-channel interaction which can be characterized by two different rangesd _int andD ₁. For a mean channel distanced ₀d _int interaction effects are negligible, and ford ₀D ₁ all channel-voltages are equal and thus represent a mean-field for the channels. Increasing conductivity of the medium decreasesd _int and increasesD ₁. With experimental data on sodium channels in nerve membranes we find:d _intd ₀, i.e. a 50% decrease of the channel-voltages by the interaction, andD ₁10³10⁴ d ₀, which indicates mean-field behaviour of the channels. In a subsequent paper we shall treat the statistics of channels which open and close stochastically under the influence of the local membrane voltage.     

The phonon spectrum of high energy heat pulses generated in thin metal films

The phonon spectrum of high energy heat pulses (10⁴W/cm²) generated by current pulses in thin evaporated metal films was studied in ruby by time resolved optical spectroscopy. The experiments show that the population temperature of the phonon states rises with rising phonon energies in accordance with theoretical predictions of Perrin and Budd [1, 2]. The thermalization of the phonon spectrum needs a time of approximately 900 µs in ruby flushed with cold helium gas.This work was supported by the Deutsche Forschungsgemeinschaft, SFB65     

Unexpected solids from enantiopure cationic palladium complexes and racemic anions: A structural study of chiral non-discrimination

Enantiomerically pure cationic complexes were obtained via cyclopalladation of primary amines and subsequent addition of a chelating ethylendiamine ligand. No diastereomeric resolution was observed upon combining these cations with racemic mandelate or hydratropate anions, but four less popular products, namely three double salts and a solid solution, were obtained and structurally characterized. For one of the double salts, the alternative ionic compounds based on different stereoisomers of the same residues were synthesized independently: The conventional racemic solid and both diastereomeric salts formed by enantiopure cations and anions were studied by single crystal X-ray diffraction. Lattice energy calculations confirm that the diastereomeric salts differ significantly; formation of the partially racemic double salt, however, is energetically favourable and precludes resolution.