Showing papers by "Martin Luther University of Halle-Wittenberg published in 1978"
238 citations
TL;DR: It could be shown that addition of the substrate to the enzyme-bound thiamin diphosphate is the step of the catalytic mechanism whose rate is controlled by the substrate (activator) molecule.
Abstract: The sigmoidal shape of the curve for v[S], characteristic of pyruvate decarboxylase, indicates that the catalytic activity of this enzyme is regulated by the substrate. The enzyme, which is inactive in the absence of its substrate, is activated not only by 2-oxo acids but also by 2-oxo acid amides, which cannot act as a substrate of the enzyme. Whilst the dissociation constant of the enzyme-activator complex depends on the electrophilic nature of the carbonyl group, the catalytic activity reached at saturation concentrations of the activator species is independent of the structure of the activator molecules. The mechanism of activation which proceeds via two reversible steps could be evaluated exactly by stopped-flow techniques. The kinetic parameters of the activation and deactivation reaction were estimated and the validity of the equations derived which describe the activation kinetics could be proved by comparing them with the measured data. Using glyoxylic acid as an irreversibly binding active-site marker, it could be shown that addition of the substrate to the enzyme-bound thiamin diphosphate is the step of the catalytic mechanism whose rate is controlled by the substrate (activator) molecule.
142 citations
TL;DR: The solvolytic detachment of leucine aminopeptidase from Sepharose-enzyme conjugates with multiple and single anchoring bonds has been studied under a variety of conditions by radiochemical and enzymological methods.
Abstract: The solvolytic detachment of leucine aminopeptidase from Sepharose-enzyme conjugates with multiple and single anchoring bonds has been studied under a variety of conditions by radiochemical and enzymological methods. The release of the single-point-fixed conjugate could be described by a leakage function, derived previously, yielding the first-order rate constant of the cleavage of the enzyme-matrix bond. The nucleophile hydroxylamine increased the detachment rate considerably. The release of the immobilized enzyme was incomplete in all experiments even after prolonged times. The enzyme leakage from multipoint-attached conjugates was still high enough to prohibit a long-term use of such preparations in routine work at room temperature.
72 citations
TL;DR: The mesomorphic properties of p-substituted phenyl-trans-4-n-alkyl-hexanecarboxylates and cyclohexyl-p-nalkylbenzoates are described in this article.
Abstract: Liquid Crystalline Phenyl-trans-4-n-alkylcyclohexanecarboxylates
The syntheses of p-substituted phenyl-trans-4-n-alkylcyclohexanecarboxylates 1–12 and cyclohexyl-p-n-alkylbenzoates 15–17 and their mesomorphic properties are described. p-n-Alkoxyphenyl-trans-4-n-alkylcyclohexanecarboxylates 1–8 exhibit larger thermal stability of mesophases than analogous phenylbenzoates 13. Trans-4-subst. cyclohexyl-p-n-alkylbenzoates 15–17 and S-phenyl-thiocylohexanecarboxylates 19 on the other side are less stable.
70 citations
TL;DR: Pyrimidine degradation in different organisms is presented and its presence in animals is preferentially discussed with respect to correlation between anabolic and catabolic reactions in terms of the “Molecular Correlation Concept”.
37 citations
TL;DR: In this article, a Mechanismus für die cyclisierung wird diskutiert, and an offenkettiges Produkt wird der Dithioester 5 isoliert.
33 citations
TL;DR: In this paper, the reaction of (o-lithiobenzyl)diphenylphosphine(I) with NiCl2 · TMEDA, [PdCl 2 · 2 Et2S] and [PtCl2· 2 Et 2S] produces cyclometalated complexes II, III and IV.
33 citations
TL;DR: In this paper, the isomeric 3 H -1,3-benzazarsoles are synthesized from secondary o -aminophenylarsines and N -phenylimide chlorides.
32 citations
TL;DR: The densities of cholesteryl myristate were measured in the smectic, cholesteric, blue and isotropic phase as mentioned in this paper, which points to a phase transition of second order.
Abstract: The densities of cholesteryl myristate were measured in the smectic, cholesteric, blue and isotropic phase. At the transitions smectic/cholesteric and bluelisotropic within the temperature interval of 0.01 to 0.02°K discontinuities in the density curves occured. which indicate phase transitions of first order. At the transition cholesteric/blue only a change in the expansion coefficients was observed. which points to a phase transition of second order. Die Dichten von Cholesterylmyristinat wurden in der smektischen, cholesterinischen, blauen und isotropen Phase gemessen. An den Umwandlungen smektisch/cholesterinisch und blau/isotrop treten innerhalb eines Temperdturintervah von 0,O1 bis 0.02°K Diskontinuitaten in den Dichtekurven auf. welche Phasenumwandlungen 1. Ordnung anzeigen. An der Umwandlung cholesterinisch/blau ist nur eine anderung in den Ausdehnungskoeffizienten vorhanden, welche auf eine Phasenumwandlung 2. Ordnung hinweist.
32 citations
29 citations
TL;DR: Acylketene S,S-acetals 1 react with hydrazines, semicarbazide, and benzhydrazide to yield tautomeric or isomeric pyrazoles 8 and 10, respectively as mentioned in this paper.
Abstract: Acylketene S,S- and Acylketene S,N-Acetals as Buildingsets for Heterocycles: Pyrazoles and Isoxazoles
Acylketene S,S-acetals 1 react with hydrazines, semicarbazide, and benzhydrazide to yield tautomeric or isomeric pyrazoles 8 and 10, respectively. On the other hand cyclisation to the aminopyrazoles 9 is possible. The pyrazoles 8 are also obtained by reaction of the dithioesters 2 with hydrazine in the presence of mercury oxide. 3(5)-Aminopyrazoles 17 can be synthesized in three different ways: from the acylketene S,N-acetals 3, from the thioamides 4 or from the acylketene N,N-acetals 5 and hydrazine. The reaction of 3 with phenylhydrazine and p-nitrophenylhydrazine leads to the 5-aminopyrazoles 20, but 8e and 9d are formed by the elimination of 1 mol arylamine. The dependence of the reaction way on the kind of the used hydrazine is discussed. The reaction of acylketene S,S-acetals 1 and S,N-acetals 3 with hydroxylamine affords isoxazoles 21 and 22.
TL;DR: In this article, the Mannich reaction was used to obtain α-Dialkylaminomethylphosphines and corresponding arsines, which showed a similar reactivity as N,N-acetals.
TL;DR: In the late Palaezoic red beds tetrapod footprints are, both in vertical and lateral extent, the most common fossils as mentioned in this paper, and they are at present most fully known from the European Rotliegend.
TL;DR: In this paper, a comparative study of Teucrium inflorescences and flowers demonstrates morphological differentiations between related groups, and a new classification of the genus Teucropsis is proposed.
TL;DR: The new species Erysiphe magnicellulata sp.
Abstract: In der vorliegenden Arbeit wird die Art Erysiphe magnicellulata sp. nov. beschrieben und die Kombination Phyllactinia mali (Duby) comb. nov. aufgestellt.
Im Rahmen einer nomenklatorischen Untersuchung der Sektionsgliederung der europaischen Erysiphaceen-Gattungen werden folgende Neubeschreibungen und Kombinationen vorgenommen: Erysiphe (DC.) Fr. sect. Golovinomyces sect. nov., E. sect. Blumeria (Golovin ex Speer) stat. nov., Sphaerotheca Lev. sect. Magnicellulatae sect. nov., Podosphaera Kunze sect. Tridactyla sect. nov., Microsphaera Lev. sect. Trichocladioidea sect. nov., M. sect. Arthrocladiella (Vassilkov) stat. nov. und Uncinula Lev. sect. Sawadaea (Miyabe in Sawada) stat. nov.
In the present paper the new species Erysiphe magnicellulata sp. nov. is described and the combination Phyllactinia mali (Duby) comb. nov. is stated.
In the result of a study about the nomenclature of the delimination of European mildew genera in sections the following new descriptions and combinations are established: Erysiphe (DC.) Fr. sect. Golovinomyces sect. nov., E. sect. Blumeria (Golovin ex Speer) stat. nov., Sphaerotheca Lev. sect. Magnicellulatae sect. nov., Podosphaera Kunze sect. Tridactyla sect. nov., Microsphaera Lev. sect. Trichocladioidea sect. nov., M. sect. Arthrocladiella (Vassilkov) stat. nov. and Uncinula Lev. sect. Sawadaea (Miyabe in Sawada) stat. nov.
TL;DR: The paramutation processes in sulf+sulf heterozygotes are restricted to a small group of cells during a short period of about three cell generations after seed germination and expansion of the cotyledons, which causes the occurrence of rather large and well defined sectors of paramutant tissue.
Abstract: 1.
In tomato plants heterozygous for a mutant allele of the sulfurea (sulf) locus paramutation may take place: under the influence of a paramutant sulf allele, the paramutable wild type allele sulf+, which is present in the same nucleus, is heritably altered with a definite frequency to a sulf mutant allele, either of the sulfpuraor the sulfvaggroup.
2.
A number of the sulf+sulf heterozygotes remain entirely green during their whole ontogenetic development (type I plants, without paramutation). However, others of the plants become variegated: these variegated plants contain-apart from green sectors — only yellow-green speckled sulfvagsectors (type II plants), or only pure yellow sulfpurasectors (type III plants) or both sulfvagand sulfpurasectors side by side (type IV plants).
3.
For all variegated plants (types II, III and IV) we determined the sizes of the green and of the paramutant sulfvagand sulfpurasectors and made a statistical analysis of the values obtained.
4.
We conducted observations over a period of three years and obtained following findings: type II plants (with sulfvagsectors) have an average size of the paramutant sectors of 27.9% (the whole plant being 100%). Type III plants (with sulfpurasectors) have an average sector's size of 25.7%, whereas the size of the paramutant sectors in type IV plants (with both sulfvagand sulfpurasectors) amounts to 54.4% (35.7% sulfvagand 18.7% sulfpura). Thus, the occurrence of tissues of both phenotypes in one plant has, on the average, been found to be correlated with a doubling of the proportion of paramutant sectors in that plant.
5.
Within sulf+sulf heterozygotes there is, in general, a positive correlation between the frequency of paramutant plants and the proportion of paramutant sectors within the plants. This is mainly due to the fact that there is a significant positive correlation between the frequency of type IV plants and the frequency of paramutant plants, i.e. the more plants within a progeny variegated, the greater the frequency of type IV plants containing both sulfvagand sulfpurasectors.
6.
These findings (mathematically analysed and compared with the consequences of several models) may result in the following concept: the paramutation processes in sulf+sulf heterozygotes are restricted to a small group of cells (16 cells at the most) during a short period of about three cell generations after seed germination and expansion of the cotyledons. In the course of which, the probability for the occurrence of paramutation decreases rather quickly from one cell generation to the next. These characteristics of paramutation processes mentioned cause the occurrence of rather large and well defined sectors of paramutant tissue.
TL;DR: In this paper, a pseudopotential calculation for metallic beryllium spectra of different polarizations, the Compton profiles for several directions, and the APS are calculated.
Abstract: Starting from a pseudopotential calculation for metallic beryllium the K-emission spectra of different polarizations, the Compton profiles for several directions, and the APS are calculated. Besides the shape of the emission spectra also the absolute values of the intensity are highly anisotropic due to the existence of localized charges along the hexagonal axis of Be. The calculated spectra agree well with a recently published measurement. The Compton profiles for three directions are calculated in momentum approximation. The comparison of the anisotropies obtained with those of several measurements and a LCAO calculation shows a good correlation.
Ausgehend von einer Pseudopotentialrechnung fur metallisches Beryllium werden die K-Emissionsspektren verschiedener Polarisationen, die Comptonprofile unterschiedlicher Richtungen sowie das AP-Spektrum berechnet. Neben der Form der Emissionsspektren ist auch die Absolutintensitat wegen der Existenz lokalisierter Ladungen in Richtung der c-Achse im Be stark anisotrop. Die berechneten Spektreen stehen im Einklang mit einer kurzlich veroffentlichten Messung. Die Comptonprofile werden fur drei Richtungen in Impulsnaherung berechnet. Der Vergleich der Anisotropien mit verschiedenen Messungen und einer LCAO-Rechnung zeigt eine sehr gute Ubereinstimmung.
TL;DR: In this article, the recovery and recrystallisation behavior of cold rolled Ni of different purity such as Ni doped with Sb, Ti and B between room temperature and 550°C was studied by measurement of the peak counting rate of 2γ-angular correlation during annealing with constant heating rate.
TL;DR: Experiments in vitro demonstrate, that there are different patterns of PG-biosynthesis in the corpus luteum and in the follicles containing cortical substance of the human ovary, and by means of indomethacin the formation of all three examined prostaglandins can be prevented almost completely.
TL;DR: Acylketene S,S- and acylketene s,N-acetals as Buildingsets for Heterocycles: 5-Cyanopyrimidines as discussed by the authors.
Abstract: Acylketene S,S- and Acylketene S,N-acetals as Buildingsets for Heterocycles: 5-Cyanopyrimidines
Acylketene S,S-acetals 1 react with amidines, guanidine or S-alkylisothioureas in the presence of triethylamine to give 4-methylthio-5-cyanopyrimidines 4–6. 4-Anilino-5-cyanopyrimidines 7 have been synthesized from the acylketene-S,N-acetals 2 under similiar conditions. The treatment of 1 with guanidine and acetamidine, respectively, in alcoholic sodium ethoxide solution yields 4-ethoxy-5-cyanopyrimidines 10. The i.r.- and 1H-n.m.r.-spectra of the synthesized compounds are discussed.
TL;DR: In the hyphae of Penicillium cyclopium the in vitro measurable activities of 3 enzymes of alkaloid biosynthesis are induced endogenously during alkaloids biosynthesis.
TL;DR: In this article, the authors isolated GA 1 and GA 3 from Triticum aestivum and Secale cereale and identified their nature with a high-resolving mass spectrometer.
TL;DR: In this article, a new P-P-Bicyclo[3.3.0] octans is introduced, which verhalt sich gegenuber nucleophilen wie auch elektrophilen Agentien als bemerkenswert stabile Verbindung.
Abstract: Im Verlauf der Metallierung der Alkylen-bis-phosphine H2P-(CH2) n -PH2 bzw. RHP-(CH2) n -PH2 (n = 2–5) erfolgt H2-Eliminierung unter Knuipfung von P–P-Bindungen. Im Falle von Verbindungen mit n = 2 und 5 resultieren P-Polymere, mit n = 4 erfolgt teilweise Ringschlus zu 1-Lithium-1,2-diphosphorinan und mit n = 3 bilden sich ausschlieslich 1-Lithiumsubstituierte 1,2-Diphospholane. Letztere reprasentieren geeignete Ausgangssubstanzen zur Synthese verschieden substituierter 1,2-Diphospholane sowie des 1,5-Diphosphabicyclo[3.3.0]octans. Dieser neuartige P–P-Bicyclus, ohne weitere Heteroatome, verhalt sich gegenuber nucleophilen wie auch elektrophilen Agentien als bemerkenswert stabile Verbindung. Die Struktur der dargestellten Verbindungen wird anhand von P-Derivaten sowie NMR- und massenspektroskopisch gesichert. In the course of the metallation of alkylene-bis-phosphines, H2P-(CH2) n -PH2 and RHP-(CH2) n -PH2, respectively (n = 2 to 5), hydrogen is eliminated under simultaneous formation of P-P bond...
TL;DR: In this paper, a consistent model of density of states for the FeNi alloys is proposed based on the band theory of ferromagnetism and some known properties of the electronic band structure of the first series transition metals.
Abstract: XPS spectra of FeNi alloys are measured. Using the spectroscopic, thermodynamic, and magnetic moment data so far available a consistent model of density of states for the FeNi alloys is proposed. This model is based on the band theory of ferromagnetism and some known properties of the electronic band structure of the first series transition metals. The measured XPS valence band spectra can be explained by means of the model DOS neglecting the influence of the transition probabilities. The CPA calculations so far available for FeNi do not fit the spectra satisfactorily. The model assumes the d-bands to penetrate each other. The up-spin bands are shifted against the down-spin bands by a rigid exchange splitting corresponding to the measured atomic magneton number in the alloy. The model neglects the spin–orbit coupling which would couple states of opposite spin but this influence should be small.
XPS-Spektren von FeNi-Legierungen werden gemessen. Unter Benutzung bisher erhaltlicher spektroskopischer, thermodynamischer und magnetischer Werte wird ein konsistentes Modell der Zustandsdichte fur FeNi-Legierungen vorgeschlagen. Dieses Modell beruht auf der Bandertheorie des Ferromagnetismus sowie einigen bekannten Eigenschaften der elektronischen Bandstruktur der Ubergangsmetalle der ersten Reihe. Die gemessenen XPS-Valenzbandspektren lassen sich mit der Modell-DOS unter Vernachlassigung des Einflusses der Ubergangswahrscheinlichkeit erklaren. Das Modell nimmt an, das sich die d-Bander durchdringen. Die Bander mit Aufwartsspin werden gegenuber den Bandern mit Abwartsspin um eine feste Austauschaufspaltung verschoben, entsprechend der gemessenen atomaren Magnetonenzahl in der Legierung. Das Modell vernachlassigt die Spin–Bahn-Wechselwirkung, die Zustande mit entgegengesetztem Spin koppeln wurde, jedoch sollte dieser Effekt klein sein.
TL;DR: The high sensitivity of these methods was used to show the absence of fraction I protein in a plastid ribosome-deficient mutant and there is a linear correlation between protein concentration and the heigh of peaks in the case of electro immunodiffusion and between protein concentrations and the area enclosed by immunoprecipitates in the cases of crossed immunoelectrophoresis.