540 Chemie und zugeordnete Wissenschaften
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Induction of the enzyme Δ5-3-ketosteroid isomerase in Pseudomonas testosteroni was found to be strongly inhibited by reserpine and by the alkaloids of Vinca and Ergot. Morphine, colchicine and papaverine caused weaker inhibition whilst a series of other alkaloids were almost ineffective. Ergot alkaloids were inhibitory towards all steroids tested, androgens, oestrogens and progestagens, and a similar effect was shown with the other inducible enzymes, 3α- and 3β.17β-hydroxysteroid-dehydrogenase.
Experiments with cell-free protein synthesis indicate that reserpine inhibits the induction of messenger RNA.
The effect of NNMG on the template activities of different polynucleotides (polyuridylic acid, polycytidylic acid, polyadenylic acid and copolymer of adenylic and guanylic acid 5,5:1) and t-RNS was studied. The maximum inhibition of the messenger activity was found for poly-C, followed by poly-Α and poly-U. The acceptor activity of t-RNA was found to be inhibited by NNMG: maximum for proline, followed by serine, leucine, phenylalanine and lysine. The mechanism of these inhibitions was studied using NNMG radioactively labelled on the methyl group. Different amounts of radioactivity were found in the various polynucleotides and t-RNS.
Following treatment with the β-galactosidase inducer [methyl-3H] -thiogalactoside, an induceracceptor-complex was isolated from extracts of E. coli K 12 using DEAE cellulose chromatography. Enzymatic digestion with trypsin suggested that the inducer was bound to a protein component.
Specific radioactive peaks demonstrated acceptor activity in the inducible strains E. coli K 12 and ML 3, but different results were obtained using the non-inducible mutants ML 35, ML 308 and ML 309.
The potent inhibitor of TMG-induction, o-nitrophenylfucoside, reduced the radioactive acceptor peak and caused a similar inhibition of β-galactosidase synthesis, p-nitrophenylfucoside was ineffective.
Further evidence is presented for the in vitro formation of an inducer-acceptor-complex in cell free extracts of E. coli K 12.
The trifluoroacetylation of thymidine at room temperature was performed using trifluoroacetic acid phenylester in pyridine. A selective protection of the 5′-position was not possible: Even low molar quantities of the trifluoroacetylating agent gave rise to bis-trifluoroacetylation. The bis-trifluoroacetyl derivatives of thymidine and 5-bromo-deoxyuridine were purified by vacuum sublimation. The completely trifluoroacetylated deoxyribosides of uracil, 5-iodouracil and adenine underwent decomposition during sublimation.
The non-specific inhibition of the poly U directed polymerisation of phenylalanine through polyanions was studied. This inhibition was found to be in order as follows: dextransulfate, polyethylensulfate, heparine, ribosomal RNA and alginate. It was found that poly A, poly AP and poly AG cause a specific inhibition of the poly U directed synthesis of polyphenylalanine. Poly AG and poly AP, but not poly A were found to inhibit the poly C directed polymerisation of proline as well. The mechanism of these two types of inhibition caused by polyanions has been discussed.
It is possible to determine the anomeric configuration of nucleosides by a simple, spectrophotometric assay, using the nucleoside phosphorylase activity of cell-free extracts from E. coli. β-nucleo-sides are split, a-anomers remain unchanged. For a single estimation 20-40 µg of nucleoside are required. 6-Azauracil- and 8-azaguanine-β-ᴅ-riboside and some nucleoside phosphates are resistant, a fact, which is of interest in view of the specificity of nucleoside phosphorylases.
Gegenstand der vorliegenden Untersuchung ist das hydrolytische Verhalten von Glycyl-seryl-alanin beim Erhitzen in einer rein wäßrigen Lösung bei einem pH-Wert in der Nähe des isoelektrischen Punktes. Die Reaktionsmöglichkeiten des Tripeptids und aller Folgeprodukte, die Alanin enthalten, wurden qualitativ aufgeklärt und die kinetischen Daten der einzelnen Reaktionen durch quantitative Hydrolyseversuche an den mit dem Kohlenstoffisotop 14C geeignet radioaktiv markierten Verbindungen Glycyl-seryl-alanin, Seryl-alanin, Alanyl-serin und Seryl-alanyl-diketopiperazin bei mehreren Temperaturen zwischen 55 und 95 °C bestimmt. Die Trennung der Hydrolysatproben erfolgte mit Hilfe der Papierchromatographie bzw. der Papierelektrophorese; für die Konzentrationsbestimmung der radioaktiven Substanzen wurde ein Verfahren ausgearbeitet, das eine Radioaktivitätsmessung mit hoher reproduzierbarer Ausbeute direkt auf den zur Trennung benutzten Filterpapieren nach der Flüssigkeitsszintillations-Methode ermöglicht.
Alle beobachteten Reaktionen verlaufen unter den Versuchsbedingungen nach einem Zeitgesetz 1. Ordnung. Die Konzentrations-Zeit-Funktionen der einzelnen Reaktionsteilnehmer wurden durch Auflösung der simultanen linearen Differentialgleichungen 1. Ordnung bestimmt und zur Berechnung der Reaktionsgeschwindigkeits-Konstanten nach einem iterativen Ausgleichsverfahren herangezogen.
In der Diskussion wird versucht, die beobachteten thermodynamischen Daten in ihrer Größenordnung aus anderen Eigenschaften und aus der Molekularstruktur der einzelnen Verbindungen abzuleiten und durch bestimmte Reaktionsmechanismen zu interpretieren.
LANGEVIN equations of the type dn× (t)/dtn+...+c × (t)=K (t) constitute the starting point of a phenomenological fluctuation theory of irreversible processes. These equations are not constructed from transport equations (as in the older theory), but via a generalized MASTER equation from phase space mechanics. The MARKOFF processes of first and higher order defined by the various LANGEVIN equations are studied by the prediction theory of stationary stochastic processes. Instead of the variation principle of the ONSAGEB–MACHLUP theory one has the minimization of the prediction error. The mean relaxation path and the entropy of the considered processes are calculated. It is shown that the entropy consists of one part which is given by the relaxation path and another which is determined by the prediction error.
Die „Selbstenergien“ Gn in 1 wurden durch näherungsweise Auswertung einer größeren Klasse von Selbstenergiediagrammen approximativ berechnet. Das Gleichungssystem (3.3) in 1 für die renormierten Semiinvarianten wurde umgeformt und durch zusätzliche Näherungsannahmen vereinfacht. Durch Näherungsansätze für die Semiinvarianten M2, M3,... konnten einfache Gleichungen für die Magnetisierung M1 hergeleitet werden. Diese Gleichungen wurden numerisch gelöst. Auf der Grundlage der Beziehungen (3.5) und (4.8) in 1 wurden ferner die innere Energie, die freie Energie und die Atomwärme des zweidimensionalen Ising-Ferromagneten sowie die Druck-Dichte-Isothermen des zweidimensionalen Gittergases numerisch ausgerechnet.