Volume 27, Issue 2

The decomposition of H 2 O 2 , catalyzed by the Co 2 ® complex of 4,4′,4″,4″′-tetrasulfophthalocyanine (Co II PTS), was investigated in the pH range 3.8 through 10 by measuring the initial rate, v 0 =d(O 2 )/dt, of the increasing formation of O 2 (25°; I=0.1). In this pH range v 0 is proportional to the initial concentration of H 2 O 2 (determined at pH 5.0 and 9.2). Due to the dimerization (log KD=5.47 ±0.09 at natural ionic strength and about 7.63 ±0.16 in 0.1 M NaClO 4 ; 25°) and polymerization of Co II PTS the catalyst and its reaction order are difficult to establish: Based on the experimental evidence it is suggested that v 0 is proportional to the concentration of monomer Co II PTS. Additionally, there is evidence that the experimentally determined v 0 contains the contributions of a pH-independent and a pH-dependent reaction course. These results are analog to those obtained earlier with Fe III PTS as catalyst. A mechanism for the catalyzed disproportionation of H 2 O 2 by CoIIPTS is proposed. The catalase-like activity of Co III PTS (OH) is smaller than that of Co II PTS and the pH-dependence is different.

The following heterogeneous exchange equilibria have been examined for isotopic effects: CaCO 3 /Ca (aq.) 2⊕ . Ca-GBHA/Ca (aq.) 2⊕ and Ca (Dowex 50) 2⊕ /Ca (aq.) 2⊕ (GBHA = glyoxal-bis (2-hydroxyanil)). The isotopic ratios 44 Ca/ 40 Ca and 48 Ca/ 40 Ca were determined by means of a mass spectrometer with a thermal ion source. In the system CaCO 3 /Ca (aq.) 2⊕ , the elementary separation factor was found to be less than 1‰ or 0,5‰ per mass unit, respectively. For the exchange in the system Ca-GBHA/Ca (aq.) 2⊕ in the concentration range from 0.011 to 0.84 M an elementary separation factor less than 1‰ per mass unit was found; from a three-stage experiment at a calcium concentration of 1.23 M it was concluded that the elementary isotopic effect is less than 0.4‰ per mass unit. Therefore no isotopic fractionation is to be expected for precipitation of inorganic or organic calcium salts. An enrichment of the heavier calcium isotopes in the solution was found in the case of the exchange in a Dowex 50-X12 loaded column. The isotopic effect depends on the concentration of the hydrochloric acid used as the eluent.

The polarographic behaviour of [(C 2 H 5 ) 4 N] ⊕ [Fe(CO) 3 NO ⊖ ] has been investigated at the mercury dropping electrode and platinum stationary electrode. It was found that the complex displays two anodic and one cathodic waves. On the basis of the results obtained a mechanism is proposed and discussed.

The hitherto unknown dimeric halogen iron tricarbonyls [Fe(CO) 3 X] 2 (X = Br, I) have been prepared by reacting HBr or HI with Fe 2 (CO) 9 and by the photoreaction of Fe(CO) 5 with HBr. The properties of these compounds are discussed.

It ought to be shown by the EHT-method and nmr-spectroscopic investigations that the dimerisation of 2-ethyl-keten-carbonic-acidethylester behaves like a cycloaddition.

α-Acyl-α-cyanocarbonyl-phenylhydrazones are effective uncouplers of oxidative phosphorylation. The pl 50 -values of a series of 60 hydrazones with substituent variations in six positions of the molecule were determined in rat liver mitochondria. They ranged from 4.96 to 7.06. The biological data together with physico-chemical compound and substituent parameters were analysed by multiple regression techniques to establish the structure activity relationship. The integral parameters pK a and log P (partition coefficient) gave correlations of only moderate significance. Good agreement of found and calculated pl 50 -values was obtained by an equation with electronic (σ) and hydrophobic (π) substituent parameters in linear and quadratic terms. It is concluded that the contribution of a substituent to uncoupling activity depends on its position in the molecule. The activity is enhanced by hydrophobic shielding of the acidic NH-group. The relevancy of these results in relation to current theories on the mechanism of oxidative phosphorylation is discussed.

If it is assumed that the oscillating O 2 flash yield sequence of algae and chloroplasts predominantly reflects an inherent property of the O 2 evolving system of the photosynthetic apparatus it is shown that the OH-radical model (O 2 production by recombination of four OH radicals) is contradictory to the experimental results because it predicts an aperiodic O 2 flash yield sequence. Several experimental facts already known strongly indicate that the OH-radical model is not consistent with the kinetic model for O 2 evolution of K OK et al. either.

By immunochemical methods we had presented evidence for a primary acceptor complex for photosystem I of photosynthetic electron transport. During purification of this complex, obtained as a water soluble fraction from ether treated lyophilized chloroplasts, two low molecular fractions are also obtained, which may or may not have relation to the primary acceptor. The purification and identification of these low molecular fractions is reported. One, absorbing at 275 and 335 nm, consists of several flavonoid glycosides. The aglycon of the main component is tentatively identified as a 3-methyl-6,7-methylenedioxy-quercetagetin. The chromophore of the other low molecular fraction, absorbing at 312 nm, contains two cinnamic acid derivatives, which on alkaline hydrolysis yield p-coumaric acid. The relation of the two low molecular fractions to other fractions of various activity isolated from chloroplasts is discussed.

Cellfree extracts from Chlorella, spinach leaves or spinach chloroplasts convert radioactive sulfate into a S-sulfocompound already in the dark. The reaction requires ATP, Mg 2⊕ ions and compounds with SH groups. The later are needed for activation of the enzym and as substrates and acceptors for the sulfogroup. The compound formed if glutathion is used has been identified as S-sulfoglutathion. Other products formed from sulfate and ATP in the dark by spinach or chlorella extracts are APS and PAPS. The formation of PAPS requires the presence of a SH-group. Both cellfree extracts transfer the sulfate group from APS and PAPS onto glutathion to form S-sulfoglutathion. No ATP is needed in this reaction, neither with PAPS nor with APS as substrate.

Light scattering measurements performed on DNA after irradiation in the presence of psoralen clearly show that inter strand cross linkings are present in the macromolecule. In fact after heat denaturation and successive cooling irradiated macromolecule shows a molecular weight practically unchanged while a DNA sample after the same treatment shows a molecular weight half of the intact native DNA. Also the general conformation of irradiated DNA undergoes practically to no modifications after the same heat treatment while native DNA shows itself to have been strongly modified. Moreover, on the basis of flow dichroism determinations, DNA cross-linked by psoralen after heat denaturation showed to be able to restore its ordered double helix structure, during the successive cooling.

The Possibility that “in vivo” a binding takes place between DNA and benz [a] pyrene was examined. After oral administration of 3 H-benz [a] pyrene, radioactive DNA was isolated from the skin, spleen and liver of NCLmice, and especially from the liver. This suggest that covalent binding between DNA and benz [a] pyrene takes place.