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ncubation of class II chloroplasts of spinach with copper in the light at pH = 8 in concentrations that inhibit oxygen evolution results in the formation of a copper (II) protein complex with the photosynthetic membrane. The EPR spectra indicate that the four nearest ligands to Cu(II) consist of three oxygen atoms and one nitrogen atom. The copper (II) protein appears to be pre dominantly associated with photosystem II. The formation of this protein as measured by the EPR signal amplitude of its room temperature spectrum correlates with the inhibition of oxygen evolution and of electron transport within photosystem I. This result indicates that the inhibition of photosynthetic electron transport by copper may be due to the formation of a copper (II) chelate with a membrane protein.
With new X-ray data from a crystal of stoichiometric K0.33MoO3 the crystal structure of this compound was refined until R(anisotropic) = 0.023. The characteristic distortion of the Mo-O octahedra is discussed.
Über das Verhalten von silicium- und zinnorganischen Verbindungen bei der Synthese von Heterocyclen
(1977)
The isocyanates of silicon (CH3)2Si(NCO)2 and Si(NCO)4 react with CH3N[Sn(CH3)3]2 and N[Sn(CH3)3]3 to yield the cyclic derivatives 2a-2b as well as the spiro compound 3. The structures of the compounds are discussed on the basis of 1H NMR and IR data. Mass spectra are not conclusive for assigning a certain structure. SO2(NCO)2 and (CH3)3Si-S-Si(CH3)3 form a cyclic compound 4 which contains two sulfur atoms of coordination number two and four. The results of the mass spectra can be interpreted by assuming that a rearrangement occurred. 4 hydrolyses under formation of 5.
CH3P(S)(NCO)2 reacts with [(CH3)3Si]2N-CH3, [(CH3)3SiNCH3]2CO and [(CH3)3Sn]3N to give the cyclic compounds 2a-2c. The structures are discussed on the basis of NMR and IR data. In 2 a and 2 b the (CH3)3Si-groups are easily and quantitatively replaced by protons with water under formation of (CH3)3Si-O-Si(CH3)3. By the reaction of CH3P(S)(NCO)2 with [(CH3)3Si]2S 4 is obtained, a cyclic compound with a sulfur atom of coordination number 2.
FP(S)(NCS)2 was used to investigate the scope of these reactions. With [(CH3)3Si]2NCH3 and FP(S)(NCS)2 5 is obtained, which reacts with S2Cl2 to yield 6, a bridged disulfur compound. This method may be useful for the systematic investigation of new cyclic compounds.
As[N(CH3)2]3 reacts with the following isocyanates: FSO2NCO, n-C4F9SO2NCO, SO2(NCO)2 and (CH3)3SiNCO. The products which result from reaction of FSO2NCO and n-C4F9SO2NCO are the acyclic tri- and bisubstituted arsines [xxx]
In contrast, SO2(NCO)2 and (CH3)3SiNCO form eight- and four-membered ring compounds, where the skeleton consists of the atoms As2S2N4 (3) and As2N2 (4). The new compounds were characterized by NMR and mass spectra.
Testosterone degrading enzymes are synthesized de novo by bacterium P. testosteroni to utilize testosterone-like steroids as the only source of carbon. RNA-synthesis of the whole lysate of testosterone-induced bacteria was found to be 15% reduced compared to the control, suggesting a cytoplasmatic factor which modulates chromatin associated RNA-polymerase activity.
Diadamantyldioxetane, trim ethyldioxetane and tetram ethyldioxetane were photolyzed b y light of A > 260 nm . The spectral distribution o f the quanta emitted during photoinduced decom position of dioxatenes was found to be different from fluorescence and phosphorescence o f ketones. Flash photolysis experim ents showed the absorption of an short-lived interm ediate. It was concluded, therefore, that photolysis o fdioxetanes is not a concerted process but involves at least one precursor o f the final product ketone.
[ω- (3-Acetylpyridinio) -n-alkyl] adenosine pyrophosphates are coenzyme analogs of NAD⊕. The adenosine pyrophosphate moiety and the 3-acetylpyridine ring of the analogs are connected by n-alkyl chains of different lengths (ethyl -hexyl). The analogs form strong dissociating complexes with lactate dehydrogenase. The complex formation is predominantly achieved by interaction of the ADP moiety with its respective binding domain at the active site.
The redox potentials of the analogs and NAD are of similar magnitude. The coenzyme function of the analogs depends upon the length of the hydrocarbon chain. Lactate dehydrogenase and alcohol dehydrogenases from yeast and horse liver do not catalize hydrogen transfer from their substrates to any other alkyl analog but [4- (3-acetylpyridinio)-n-butyl] adenosine pyrophosphate, aldehyde dehydrogenase from horse liver catalizes hydrogen transfer from acetaldehyde to the pentyl derivative and glyceraldehyde-3-phosphate dehydrogenase catalizes hydrogen transfer to both analogs. In no case, hydrogen transfer from or to one of the 3-acetylpyridine-n-alkyl analogs proceeded with a velocity comparable to NAD or its 3-acetylpyridine analog. The results show that the nicotinamide bound ribose in NAD is involved in the binding and the activation of the coenzyme.
A single procedure for the preparation of lactate dehydrogenase (EC 1.1.1.27), the mitochondrial and cytoplasmic forms of malate dehydrogenase (EC 1.1.1.37), adenylate kinase (EC 2.7.4.3) and pyruvate kinase (EC 2.7.1.40) from pig heart is described. The five enzymes are obtained in preparative amounts in homogenous form with specific activities equal to or higher than those pre viously reported. Some molecular properties of pig heart pyruvate kinase are determined.
The NAD analogue [3-(3-acetylpyridinio)-propyl] adenosine pyrophosphate forms enzymically inactive complexes with glyceraldehyde-3-phosphate dehydrogenase from yeast and rabbit skeletal muscle. In the latter enzyme four mol of the analogue are bound with equal affinity inhibiting the enzyme in a competitive way: KI = 0.3 mM as compared to the dissociation constant KD=O.6 mм.
The brominated derivative [3- (3-bromoacetylpyridinio) -propyl] adenosine pyrophosphate is covalently bound to both enzymes causing irreversible loss of enzymic activity. Complete inactivation of the enzyme from muscle requires two moles of the analogue per mol of tetramer. The remaining two sites are still able to bind two mol of NAD+ without regain of enzymic activity. In the case of the yeast enzyme four mol of the analogue are bound. Inactivation of the rabbit muscle enzyme is accompanied by the disappearance of two out of four highly reactive sulfhydryl groups; in the yeast enzyme the four active site cysteine residues are still able to react with DTNB1 the reactivity being diminished significantly.
Hybrid formation between the native enzymes from yeast and skeletal muscle is not affected by the modification of the enzyme. Similarly the sedimentation properties of the covalently modified enzyme are indistinguishable from those of the native molecule. This indicates that both the native and the irreversibly inhibited enzyme are identical regarding their quaternary structure.