Band 27, Heft 5

The reactions between As 2 O 3 , As 2 O 5 , As(OC 2 H 5 ) 3 , and NH 3 above the critical point up to 3700 atm were investigated and described. The reaction products formed under various pressure and temperature conditions are compounds with arsenic-nitrogen bondings and ammonium salts of different arsenic acids. The lattice constants and the space group of NH 4 AsO 2 produced by the reaction of As 2 O 5 and NH 3 under ammonothermal conditions were determined.

The preparations of the following compounds are described: O = PF 2 N = PCl 2 N = PCl 3 , O = PF 2 N = PCl 2 N = PCl 2 N (CH 3 ) 2 , O = PF 2 N=PCl 2 N = PCl 2 N (C 2 H 5 ) 2 , O = PF 2 N = PCl 2 N (CH 3 ) 2 , O = PF 2 N = PCl 2 N (C 2 H 5 ) 2 , O = PF 2 N = PCl 2 N (CH 3 ) Si (CH 3 ) 3 , O = PF 2 N = PCl 2 NCS, O = PFClN = PCl 2 N (CH 3 ) 2 , O = PFClN = PCl 2 N (C 2 H 5 ) 2 , O = PFClN = PCl [N (C 2 H 5 ) 2 ] 2 and O =P (C 6 H 5 ) FN = PCl 3 . They were characterized by 1 H-, 19 F- and 31 P-nmr spectroscopy. Analytical, ir and mass spectral data are reported. The properties of these substances are compared with the corresponding thiophosphorylderivatives.

The isotopic effect of calcium was determined in several heterogeneous systems with the chelating resin Dowex Al. In one column experiment the dependence of the isotopic effect on the concentration of the hydrochloric acid as the eluent was studied. In the case of a 10 -2 M HCl the isotope 48 Ca was enriched in the solution. In the case of a 10 -4 M HCl an enrichment of the isotope 40 Ca was observed in the solution. This inversion of the isotopic effect can be explained by the formation of a calcium complex in the chelating resin occurring in a 10 -4 M HCl solution. In another column experiment calcium was eluated with an EDTA solution. An enrichment of the heavier calcium isotopes was found in the solution. In this case only a small separation factor was found, because calcium forms a complex in the Dowex Al resin as well as in the EDTA solution. In a static ion exchange experiment on the system Ca (DOWEX A1) 2+ /Ca (aq.) 2+ the elementary separation factor was measured. The heavier isotopes were enriched in the solution. For the ratio 44 Ca/ 40 Ca the elementary separation factor was found to be 1.0137, in the case of 48 Ca/ 40 Ca the separation factor was 1.0214.

UV Photosylis (254 nm) of 5-iodouracil in aqueous, oxygenated solution in presence of KI, FeSO 4 , KBr and K 2 SO 4 was investigated over a pH-range of 1—6. Uracil, isodialuric acid, and isobarbituric acid were identified as photoproducts. At a constant pH-value (pH=1) at high KI-concentrations (10 -1 mole/1) the main product is uracil. With decreasing KI-concentrations the yield of uracil decreases and isobarbituric acid appears as a photoproduct. On further decreasing KI-concentrations (< 10 -2 mole/1) the yield of isobarbituric acid decreases and the formation of isodialuric acid commences. UV Photolysis of iodouracil at constant KI-concentrations (10 —1 mole/1) and increasing pH (pH = 1—6) yields similar results with one exception. At higher pH-values on account of isodialuric acid at least four further compounds are formed. The yield of these products increases with increasing pH value. Addition of KBr and K 2 SO 4 has no effect on the product distribution. The possible mechanisms for the formation of the reaction products are discussed.

The synthesis of bromo-cyclobutadiene-irontricarbonyl is reported and compared with a former attempt of synthesis that yielded another product. Spectra are discussed with respect to structure and bonding properties.

The formation constants of the complexes of Mg 2+ , Ca 2+ , and Sr 2+ with 2,3-diphosphoglycerate have been determined with pH-methods according to Schwarzenbach. The enthalpies of these reactions were obtained by microcalorimetric measurements. They are positive as well as the entropies showing that the complex formation is only caused by an increasing entropy. A comparison is made with the corresponding values obtained by ANDEREGG 1 for the tripolyphosphate.

The radical scavenger 1,1-diphenyl-2-picrylhydrazyl (DPPH) in methyl iodide solution was exposed to electron-rays in the absence of air, and the products were separated by thin-layer chromatography. The substances were characterised and identified as 1,1-diphenyl-2-picrylhydrazine (1), p-nitro-diphenylamine (2), 2,6-dinitro-diphenylamine (3), 1-phenyl-1-(p-nitrophenyl)-2-picrylhydrazine (4), and 2,4,6-trinitro-aniline (5). In addition some unidentified products are formed. The mass- and ir-spectrometric analysis of the low molecular weight products indicates that they are produced by the splitting of the N — N-bond in the DPPH molecule. From the material balance and the chemical compositions of the reaction products, it is presumed that the early stage of the decomposition of DPPH induced by electron-rays is a nitration of DPPH. A mechanism is formulated to explain the formation of the compounds.

Hemocyanin of the snail helix pomatia was studied by small-angle X-ray scattering in 0.15 M phosphate buffer pH 6. The outer portion of the scattering curve showed minima, which indicated that the hemocyanin molecule is composed of a large number of identical (or very similar) nearly spherical subunits. From the position of the minima the radius of gyration R u of the subunit was calculated to be 1.55 nm; this corresponds a diameter of 4 nm assuming a spherical shape. The number of the subunits is discussed, too; a number of 330 can be given as lower limit, a number of 528 as upper limit (most propable value 350 — 400). Various models were put up by arranging the subunits (diameter 4 nm) in different ways to hollow cylinders. The theoretical scattering curves of these models were compared with the experimental one and a model equivalent in scattering is suggested for the hemocyanin Helix pomatia. In this model, which fits very well to the experimental curve, 360 subunits form a hollow cylinder. The model shows also the essential features found by electron microscopy by VAN BRUGGEN. The essential features are an arrangement of the subunits in 6 layers vertical to the cylinder axis and a 5-fold screw axis parallel to it.

Phenylmalonylchloride reacts with sodium acetate in boiling benzene if possible via a dimeric phenylketenecarboxylic acid to give 4-acetoxy-3,6,7-triphenyl-3,6-cycloheptadiene-1,2,5-trion. The structure of this compound is deduced by mass spectrometry. Analogous compounds are obtained with the sodium salts of other carboxylic acids. A reaction mechanism is proposed.

Benzylmalonyl Chloride reacts in the presence of sodium acetate in boiling benzene to give tribenzyl-phloroglucinol-triacetate, however with sodium chloroacetate to 3,5-dibenzyl-6-phenethylpyran-2,4-dion. In both cases trimerisation of benzylketene or benzylketene carboxylic acid chloride occurs. On the other hand, benzylmalonylchloride reacts with sodium benzoate and sodium phenylacetate via a dimeric benzylketene carboxylic acid chloride under the loss of phosgene to yield cyclopentadienyl derivatives.

The origin of the positive Soret Cotton effect of myoglobin was calculated by Hsu and WOODY on the basis of a mechanism taking into account the coupling of the Soret and aromatic side-chain π—π* transitions. HUBER and coworkers have worked out the atomic coordinates of a monomeric insect hemoglobin which exhibits a negative Soret Cotton effect. It seemed of some importance to examine the capability of this mechanism to explain the observed inversion of sign. The calculations resulted indeed in a negative total rotational strength (—0,2 DBM), the main contributions arising from phenylalanine residues.

A linear relationship has been found by correlating simple HMO- and McLachlan- HMO-spin densities with g-values of substituted tetraphenylcyclopentadienone (tetracyclone) metal ketyls, measured by EPR techniques. Assuming an out-of-plane angle — referred to the plane of the cyclopentadienone — of 60° for the α- and 30° for the β-phenyls the EPR data can be explained satisfactorily. This model serves as well to characterize, by means of HMO calculation, the two vis. bands of tetracyclone compounds (which are dependent on the nature of substituent) to be intramolecular charge transfer bands.

A hypothesis by Bernhauer on the biosynthesis of the benzimidazole bases of corrinoids implicates the possible existence of a corrinoid containing 6′,7′-dimethylnaphtho- (2′,3′) -imidazole-4,5 (DMNIA). In order to facilitate the detection of this corrinoid in natural sources by means of a reference compound, DMNIA was synthesized and added to cultures of Propionibacterium shermanii. Thus the new vitamin B 12 -analog DMNIA-cobamide was formed. The DMNIA-cobamide was degraded and its base isolated. This base had the same UV-spectrum and electrophoretic behaviour as the product prepared by chemical synthesis. On degradation of DMNIA-cobamide with cerous hydroxide DMNIA-α-D-ribofuranoside is formed. Perchloric acid treatment of DMNIA-cobamide yields DMNIA-α-D-ribofuranoside 3′-phosphate. The microbiological activity of DMNIA-cobamide cyanide tested with the vitamin B, 12 -requiring Lactobacillus leichmannii ATCC 7830 was equal to the activity of vitamin B 12 , with the Escherichia coli-mutant 113-3 it exhibited about 50% of the growth-activity of vitamin B 12 . DMNIA-cobamide coenzyme shows approximately 10% of the coenzymatic activity of coenzyme B 12 in the propanediol dehydrase reaction.

Between a group of non sulphydryl radioprotectors (methanol, formaldehyde, acetaldehyde, formiate, acetate, ethanol and tryptophan); ethanol and tryptophan were selected because its high protector action on irradiated purine and pyrimidine bases. At molarities of the order of 10 —4 for tryptophan-ethanol and bases and DNA the respective DRF values were: for guanine: 20.58; for adenine: 3.75; for thymine: 4.94; for cytosine: 5.52; for uracil: 5.43; and for DNA: 18.95. For irradiated seeds protected with tryptophan-ethanol (1.5 × 10 —3 M; 2.6 × 10 —2 M) the DRF value was of 3.33 and radiation damage becames evident only after a total dose of 2 × 10 4 rads. A partial different mechanisms for radioprotection with ethanol and tryptophan is postulated; this is supported by the fact that when tryptophan molarities attains that of protected DNA, there are a rapid increase in its values of DRF, crossing up the ethanol protection curve. Actually tryptophan could act not only as a radical scavenger, but also, as localized radical quenchor and/or energy trapper.

Thymine-2- 14 C was irradiated with UV light (>300 nm) in water solutions in the presence of different sensitizers. Pyrimidines upon irradiation with wavelengths of 300—320 nm in the presence of some ketones as sensitizers, yield cyclobutyl pyrimidine dimers. The reaction occurs through a triplet-triplet energy transfer from the sensitizer to the substrate. The energy transfer, however, does not occur through a simple physical mechanism. The ability of a donor (e. g. ketone molecule) in its excited state to form a complex with the acceptor (pyrimidine molecule) appears to be a prerequisite in this type of photodimerization reaction. A correlation of the photochemical behavior of different ketones in this reaction with the nature of their excited states has been proposed. Carbonyl compounds possessing n, π* lowest triples are active in inducing pyrimidine dimerizations. By introducing some different electron donating groups to the ketone molecules that lower its π, π* state below its n, π* level, the sensitizing ability of the molecule appears to decrease or disappears completely. Ethylacetoacetate was found to be a more effective sensitizer than acetone or acetophenone. Likewise, dihydroxyacetone was found to be a potent photosensitizer in dimerization of thymine. Urocanic acid (UCA), a major UV absorbing compound in mammalian skin, did not show any sensitizing ability to induce cyclobutyl pyrimidine dimers on irradiation in the presence of thymine, with wavelengths greater than 300 nm.

The distribution in the organism of the mouse of free 3 H-thymidine and 3 H-cytidine was studied 1, 2½, 5 and 15 minutes after intravenous injection into normal and pregnant mice (20 th day) using whole body autoradiography. The grain density measured over brain and fetus is 10 times smaller as compared to other tissues of the organism. This means that a blood brain barrier and placental barrier for thymidine and cytidine exists.

The tritium content of the L- and K-region of commercial available tritiated 1,2,5,6-Dibenzanthracene was measured and compared with the 3 H-release after binding of the compound to mouse skin proteins. The results exclude an addition reaction to the K- and L-region and favour a substitution reaction at one C-atom.

Embryonic rat cells cultured in a synthetic medium are stopped in G 1 phase if serum is omitted from the culture medium. On addition of calf serum these cells resume DNA synthesis after a lag phase of 15—20 hours. In the present paper the events concerning the metabolism of adenosine phosphates after stimulation by serum have been examined. The results are the following: 1. The concentration of cAMP in cells which have been incubated for 24 hours in serum-free medium is 32 times higher than that in cells growing in medium containing 10 per cent calf serum; the accumulated cAMP is metabolized within 10 min after the addition of 10 per cent calf serum. This has been confirmed by a double labelling technique after preincubation with radioactive adenosine as well as by estimation of cAMP using a protein-binding assay. 2. A cAMP-specific phosphodiesterase is activated shortly after stimulation; the enzyme activity in dialysed cell homogenates is increased within 30 min by a factor of 2. 3. Cells incubated in serum-free and those in serum-containing medium have equal amounts of ATP. On addition of serum the ATP concentration in cells preincubated in serum-free medium decreases by 27%; the original level is restored 20—30 min later.

Bud excretions of Prunus and Rhamnus species are shown to contain free flavonoid aglycones. While in Rhamnus these are the common flavonols known long ago as glycosides in berries and leaves, there are some rare aglycones to be found in Prunus avium, namely dihydrowogonin, jaceidin, 6-methoxykaempferol and its 3-methyl ether.