Volume 22, Issue 6

Bei Photoreaktionen, die in zähen Medien ablaufen, ist der Stoffumsatz eine Funktion von Ort und Zeit. Bei einfacher Geometrie von Lichtquelle und Reaktor 1 gehorcht dieser Zusammenhang einer partiellen Differentialgleichung, die für einfache Photoreaktionen geschlossen integriert werden kann.

Quarternary phosphonium salts are formed during the γ-irradiation of mixtures of triphenylphosphine (TPP) or tributylphosphine with aryl halides. The rate of conversion is markedly increased upon dilution of the mixtures with hydrocarbon solvents such as benzene, cyclohexane and cyclohexene. An ionic mechanism is discussed in which a positive charge transfer from the solvent to TPP and dissociative electron capture by the aryl halide are involved. Several phosphonium salts were synthesized. Arsonium salts are produced from triphenylarsin-arylhalide-mixtures with G-values about ten times lower than in the corresponding TPP reactions. The yield of stibonium salts is still lower. Trialkylamines react with aryl halides to give trialkyl or dialkyl ammonium salts. The rate of conversion can also be drastically increased by the addition of benzene.

In a series of publications we have described the kinetics of free-radical formation from molybdenum carbonyl in association with organic halides in a number of electron-donating solvents. Radical formation involves the displacement of carbon monoxide from the carbonyl by the solvent or vinyl monomer in a rate-determining process giving rise to complexes of the type Mo (CO) 5 L (where L represents the solvent or monomer) which then react directly with the halide. This paper describes a study of the behaviour of Mo (CO) 5 Py in association with organic halides in methyl methacrylate solution. The results show that Mo (CO) 5 Py does not react directly with the halide but first undergoes activation by reaction with monomer, mainly with displacement of pyridine. The relative reactivities of complexes of the type Mo (CO) 5 L are discussed. The mechanism previously proposed to account for the inhibition processes observed in Mo (CO) 6 -organic halide systems satisfactorily explains the extensive inhibition observed in the present work.

Ethylpolyphosphates have been prepared by reacting P 4 O 10 with either triethylorthophosphate or with ethylether. Phenylpolyphosphates were prepared from P 4 O 10 and triphenylorthophosphate at 300 °C. By the same procedure, o-kresylpolyphosphates could also be obtained, but not p-nitro-phenylpolyphosphates. The various polyphosphate esters were subjected to nuclear magnetic resonance analysis to characterize the distribution of phosphate moieties present, branching groups, middle groups, end groups, and orthophosphates. A true equilibrium between the units was found for ethylpolyphosphates and the systems could be accurately described by the theory of van Wazer. This theory does not seem to hold for the present results with polyphenylphosphates. However, the experimental data can be described quantitatively with a modified form of the theory. Ethylpolyphosphates can either phosphorylate or alkylate nucleophilic groups and alkylation is favored by the presence of protons. Only phosphorylation is observed with phenylpolyphosphates. Solvolysis of the polyphosphate esters with water or n-butanol leads to a very rapid disappearance of branching groups and a slow disappearance of the middle groups. The amount of reactive phosphorus can be calculated from the nuclear magnetic resonance data. The application of phenylpolyphosphates for a number of synthetic procedures is discussed.

Uranoxidfluoride lassen sich durch Umsetzung von UF 4 mit UO 2 und UO 3 oder U 3 O 8 unter Luftabschluß bei Temperaturen zwischen 400 und 550 °C darstellen. Dabei entstehen je nach dem Verhältnis der Ausgangsverbindungen entweder homogene Oxidfluoride mit z. T. beträchtlicher Phasenbreite, die das Uran in den Oxydationsstufen +5 oder +5 und +6 gemeinsam enthalten, oder eine stöchiometrisch zusammengesetzte Verbindung, UO 2 F 0,25 , mit vier- oder fünfwertigem Uran.

Die kürzlich erschienene Arbeit von ELVIDGE und RALPH 1 , in der die groben Werte für die Kernresonanz-spektroskopischen Parameter der drei isomeren 1.4-Dicyanobutadiene angegeben wurden, veranlaßt uns, die unabhängig durch exakte Berechnung mit Computerprogrammen ermittelten Parameter zu publizieren.

Die Positivierung der Reduktionsstufe aromatischer Nitroverbindungen in methanolischen Lösungen bei Zusatz eines Überschusses organischer Säuren wird untersucht. Es wird eine Beziehung zwischen der formalen Geschwindigkeitskonstante der Elektroreduktion und der Säurekonzentration gegeben; die Geschwindigkeitskonstante nimmt mit der Quadratwurzel aus der Säurekonzentration zu, ebenso mit der Säurestärke. Daraus wird geschlossen, daß die Positivierung durch eine Lösungsreaktion mit Wasserstoffionen hervorgerufen wird. Bei Nitroanilinen tritt eine Zweiteilung der Stufe infolge teilweiser Protonisierung der Aminogruppe auf.

N- (2-Nitrophenyl) -sulfenyl-Peptide lassen sich bei Anwesenheit von Tryptophan in der Peptidsequenz mittels Chlorwasserstoff in organischen Lösungsmitteln ohne Bildung von S- (2-Nitrophenyl) thiotriptophan-Derivaten entacylieren, wenn dem Reaktionsansatz 10 — 20 Äquivalente eines geeigneten Indolderivates, wie N-Methyl-, 2-Methylindol, Indol etc., zugesetzt werden. Ferner gelingt die Desulfenylierung unter weitestgehender Vermeidung genannter Nebenreaktion mittels hochprozentiger Thioglykolsäure.

Es werden die PMR-spektroskopischen Daten von Äthylen-Platin-Komplexen des Typs trans-(C 2 H 4 ) PtCl 2 -L angegeben und diskutiert. Unter Mitberücksichtigung von FIR-Ergebnissen können Änderungen der Olefin-Platin-Bindungsstärken durch Polarisationsänderungen gedeutet und eine starke Rehybridisierung an den olefinischen C-Atomen widerlegt werden.

As previously shown ribonuclease irradiated by γ-rays under nitrogen atmosphere may be separated by column chromatography on Sephadex into two components, one having enzymatic activity, the other consisting of aggregated products with less enzymatic activity; in the presence of air an additional inactivated component is formed. Amino acid analysis of these various products shows that in all components methionine, tyrosine, phenylalanine, lysine, and histidine are destroyed with increasing dose, whereas glycine shows a small increase. In nitrogen atmosphere, besides the amino acids mentioned, cystine is changed to a great extent; these changes occur in the active component as well as in the inactivated aggregates. The following conclusions are drawn: (1) The primary structure of an RNase molecule may be changed by irradiation without loss of enzymatic activity. (2) After irradiation in nitrogen the main part of the inactivated molecules are present as aggregates, in air a small fraction is converted primarily into denatured monomers which at higher doses show aggregation, too. (3) There are no key amino acids, the alteration of which leads to the inactivation of the enzyme molecule. (4) This conclusion holds in particular for cystine; three independent proofs are presented demonstrating clearly that inactivation of ribonuclease in aqueous solution does not occur by reactive species (generated in the water) attacking the disulphide bridges and converting the molecule from the enzymatically active to the inactivated state.

Induction of the enzyme Δ 5 -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.

In order to determine at what stage in the biosynthesis of biochanin A (5.7-dihydroxy-4′-methoxyisoflavone) and formononetin (7-hydroxy-4′-methoxyisoflavone) the methylation of the 4′-hydroxygroup occurs, the incorporation of p-methoxy-cinnamic acid-[3- 14 C-methyl-T], 4-methoxy-2′.4′-dihydroxychalcone- [β- 14 C-methyl-T] and a number of unmethylated precursors into the isoflavones of chana seedlings (Cicer arietinum L.) was compared. p-Methoxy-cinnamic acid and 4.2′.4′-Trihydroxychalcone were found to be the best precursors. Although the incorporation of p-methoxy-cinnamic acid was very good (incorporation rate 6.2%) the T/ 14 C ratio dropped by 95% upon incorporation into the isoflavones, a fact which showed that a rapid demethylation takes place in the plants. In addition, kinetic experiments were carried out with p-methoxycinnamic acid- [3- 14 C-methyl- 14 C-methyl-T] and 4-methoxy-2′.4′-dihydroxychalcone- [β -14 C-methyl- 14 C-methyl-T]. But in this case also the rapid demethylation did not permit a definite conclusion to be drawn as to the stage in the biosynthesis at which the methylation step occurs. The very good incorporation of 4.2′.4′-trihydroxycalcone- [β- 14 C] into the isoflavones (5,3% incorporation, dilution 61), however, shows that methylation can occur at a late stage in the biosynthesis.

Whole body irradiation with 800 R caused a three fold increase of radioactivity in the liver and spleen proteins of rats. Analysis of the radioactivity of the precursor pool showed an increase of 14 C-activity to the same degree as found for the proteins. Thus the increase of the incorporation rate of 14 C-glycine into the proteins is simulated, and consequently there is no change of the protein synthesis in the liver of an irradiated rat as measured with 14 C-glycine. This is probably true for the rat spleen also.

New absorption changes with a life time of 2·10 —4 sec at ∼690 nm probably represent the chlorophyll-a light reaction in photosynthesis which promotes the cleavage of water.

Thylakoids isolated from the purple bacterium Rhodopseudomonas spheroides were examined with regard to the amino acid composition of their structural proteid and the fatty acid composition of their ether soluble lipids. The fatty acid composition was nearly identical with that of the ether soluble lipids from whole cells. The main component was cis-vaccenic acid. Mono-unsaturated and saturated fatty acids with 18 and 16 C-atoms were dominating. After extraction of the lipids and washing of the thylakoids with NaCl and NaOH solutions, there remained at least two protein fractions and these could be separated by phenol-water at 65 °C. The amino acid composition of the structural proteid was similar to that of the structural proteids from thylakoids of Oscillatoria, Chlorella and green higher plants.

Blastoporal lip (presumptive notochord and myotomes) together with adjacent ectoderm (which is induced to form the neural system by the blastoporal lip) from early gastrulae was explanted and treated with 0,5—2,5 µg/ml actinomycin D for periods ranging from two hours to several days. The RNA synthesis is completely inhibited at 2,5 μg/ml Actinomycin D and partially inhibited at 0,5 μg/ml actinomycin D. At 2,5 µg/ml some notochordal cells are still formed, but the differentiation of neural tissue is completely inhibited. At 0,5 μg/ml actinomycin D notochord and muscle are more resistent than the neural tissue. The inducing capacity of the blastoporal lip is not diminished after treatment with actinomycin D. Actinomycin D must therefore impair the competence of the ectoderm to be induced by inhibiting the RNA synthesis. If tissues from tailbuds, which are already differentiating into muscle, notochord and spinal cord are explanted and treated with actinomycin D the differentiation is partially inhibited, but a differential sensitivity of these tissues is not observed. The overall rate of protein synthesis is somewhat enhanced after treatment with 0,5 μg/ml actinomycin D for 2 — 5 hours.

The precancerous state of nitrosomorpholine-induced development of hepatomas in rat liver is characterized by a reduced content of polysomal structures. Most of the ribosomes are found in the monomeric or dimeric form. In agreement with these findings, the m-RNA as well as the newly synthesized peptide chains are attached preferably to single or dimeric ribosomes. Protein synthesis is accelerated more than twofold. These alterations persist after NNM-feeding is stopped and are considered to be irreversible. It is concluded, that the phenomena described relate directly to carcinogenesis.

Physikalische und thermische Kontrastierung führt bei Fixierung in Glutaraldehyd und Einbettung in Vestopal bei Parenchymzellen der Leber zu weitgehend ähnlichen Kontrastunterschieden auch bei Mitochondrien und den Membranen des Retikulums. Beide Verfahren wirken also weitgehend unspezifisch. Von den chemischen Verfahren liefert Uranylacetat im Cytoplasma ähnliche Kontrastverhältnisse wie die beiden genannten Verfahren. Das spezifische Verhalten des Uranylacetats kann z. B. an der Kontrastierung des Chromatins demonstriert werden. Sie bleibt aus, wenn die färbbare Substanz auf der Wasseroberfläche des Messertroges herausgewaschen wurde. Bleicitrat-Kontrastierung hat hier im Gegensatz zu Uranylacetat eine spezifische Wirkung nur auf RNS-haltige Zellbestandteile.

Roccellaria mollis (HAMPE) ZAHLBR. enthält meso-Erythrit, die beiden neuen Verbindungen Mollin und Roccellin sowie die aliphatische Lactoncarbonsäure (+) -Roccellarsäure, die mit partialsynthetischer (+) -neo-Dihydroprotolichesterinsäure identisch ist.

Es wird die Isolierung und Charakterisierung von Inhaltsstoffen aus fünf Roccellaceen beschrieben. R. portentosa aus Chile enthält Lecanorsäure (I), meso-Erythrit (II) und Tetrahydroxyfettsäuren (III), R. portentosa von den Galápagos-Inseln Portentol, (+)-Roccellsäure (IV), (+)-Erythrin (V), Galapagin und Protocetrarsäure, R. gayana I, II und III, R. fimbriata V, (—)-16α-Hydroxykauran, II und III, R. babingtonii V und II und R. fucoides V, Aspicilin und IV.