Palladium and phosphomolybdovanadate catalyzed olefin oxidation to carbonyls

A new homogeneous catalyst system has been developed for the oxidation of olefins to carbonyls — ethylene to acetaldehyde and higher olefins to ketones. The catalyst system was first developed for the oxidation of ethylene to acetaldehyde in Wacker-type acetaldehyde plants. The aqueous catalyst solution has three key components. A palladium(II) catalyst oxidizes the olefin to the carbonyl, which is analogous to the Wacker system but with only a fraction of its palladium. Keggin phosphomolybdovanadates of the general formula PMo_(12–x) V _x O ₄₀ ^(3+x)– provide a dioxygen-reversible vanadium(V)/vanadium(IV) redox agent for palladium(O) reoxidation, which is analogous to the copper(II)/copper(I) chlorides in the Wacker system. Chloride at centimolar concentrations, lacking in earlier reported palladium and polyoxometalate catalyst systems, is essential to maintain stable palladium(II) catalyst activity. Kinetic characterization and reaction engineering provided ethylene and oxygen reaction rates comparable to those obtained with the Wacker catalyst. A new, efficient method of preparing aqueous phosphomolybdovanadate solutions was developed for laboratory and large-scale production. This paper describes the catalyst system and its reactions with emphasis on the polyoxometalate chemistry.     

Kidney structure and function of obligate and facultative hibernators: the white-tailed prairie dog (Cynomys leucurus) and the black-tailed prairie dog (Cynomys ludovicianus)

The white-tailed prairie dog is an obligate hibernator that enters a heterothermic phase when maintained in the cold with low intensity light and ad libitum food and water. The black-tailed prairie dog (a facultative hibernator) will not hibernate under similar conditions. It has been suggested that the black tailed prairie dog remains active during the winter because it can conserve water more effectively due to a more efficient kidney. The present study revealed no significant differences between the species in renal morphology: relative medullary thickness, nephron heterogeneity, renal vasculature, or fornix dimensions, all of which are structures associated with the urinary concentrating mechanism. In addition, there was no difference in number of nephrons between the two species. The black-tailed prairie dog does produce a more concentrated urine when food and water deprived. However, this difference was not observed when the animals were salt loaded. The water-deprivation and salt-loading experiments suggest that the higher urine osmolality produced by the back-tailed prairie dog during fasting is a result of a higher urea load due to a greater protein catabolism and not because of a differential capacity to concentrate urine.Abbreviations C cortex - GFR glomerular filtration rate - H height - IS inner stripe - IZ inner zone of medulla - L length - OS outer stripe - PE polythylene - RMT relative medullary thickness - T _a ambient temperature - W width     

Origin ofd-serine present in urine of mutant mice lackingd-amino-acid oxidase activity

Summary Urine of ddY/DAO mice lackingd-amino-acid oxidase contained 5.7 times more serine than that of normal ddY/DAO⁺ mice. Most of the serine wasd-isomer. The origin of this^d-serine was examined. Oral administration of 0.02% amoxicillin and 0.004% minocycline to the ddY/ DAO^- mice for 7 days did not reduce the urinaryd-serine, indicating that thed-serine was not of intestinal bacterial origin. When the mouse diet was changed to one with different compositions, the urinaryd-serine was considerably reduced. Furthermore, starvation of the ddY/DAO^- mice for 24 hours reduced the urinaryd-serine to 33% of the original level. These results indicate that most of the urinaryd-serine comes from the diet. However, the urine of the starved ddY/DAO^- mice still contained 4.6 times mored-serine than that of the ddY/DAO⁺ mice, suggesting a part of the D-serine have an endogenous origin.     

Synthesis of charged amphipathic nitroxide lipid spin labels and an example of their application in membrane studies

The synthesis of a series of amphipathic nitroxide lipid spin labels is reported. Thus, 12-proxylhexadecanol has been converted into the versatile fatty acid spin label 14-proxylstearic acid. This substance was used to prepare 14-proxylstearyltrimethylammonium methanesulfonate, a positively charged label, and 14-proxylstearylmethyl phosphate sodium salt, a negatively charged label. Also prepared in the doxyl series were quaternary ammonium salts derived from 16-doxyl- and 7-doxylstearic acid. The positively charged and negatively charged proxyl labels were used in a preliminary experiment to investigate the role of charge in their interaction with reconstituted cytochrome oxidase. The average binding affinity of the negatively charged label is approximately 2-fold higher than that of the positively charged label at pH 7.4. At pH 5.5 the average relative affinity for negatively charged label is about 3.5-fold higher than that of positively charged label, suggesting that the ionizable group(s) on the protein can interact with the lipid headgroup.     

The sulfhydryl groups of the thiol-dependent cytolytic toxin from Bacillus alvei evidence for one essential sulfhydryl group

Alveolysin, an extracellular protein toxin (M_r ? 63,000) excreted by Bacillus alvei and purified to homogeneity was shown to contain four cysteine residues. All thiol groups of the hemolytically active toxin preparation were free as found by direct titration by 5,5′-dithiobis (2-nitrobenzoic acid) and confirmed by the absence of disulfide bond. Toxin alkylation with tosyl lysine chloromethyl ketone resulted in the complete loss of hemolytic activity and the disappearance of only one thiol group with no modification of histidine residues. These results support the conclusion that one essential thiol group is implicated in the membrane-disrupting activity of alveolysin.     

Catalytic activity and arrangement of subunit polypeptides in rat liver cytochrome c oxidase as studied by proteolysis

Cytochrome c oxidase from rat liver was incubated with various proteinases of different specificities and the enzymic activity was measured after various incubation times. A loss of catalytic activity was found after digestion with proteinase K, aminopeptidase M and a mitochondrial proteinase from rat liver. In each case the decrease in enzymic activity was compared with the changes in intensities of the polypeptide pattern obtained after sodium dodecyl sulfate polyacrylamide gel electrophoresis. The susceptibilities of the subunit polypeptides of the soluble cytochrome c oxidase to proteinases were very different. Whereas subunit I was most susceptible, subunits V–VII were rather resistant to degradation. From the relative inaccessibility of subunits V–VII to proteinases it is likely that these polypeptides are buried in the interior of the enzyme complex.     

Inhibition of the pancreatic microsome enzyme release phenomenon by inhibitors of signal peptidase activity

The protease-sensitive release of α-amylase from rat pancreatic microsomes, incubated at 37°C, was inhibited by protease inhibitors which have been reported to inhibit signal peptidase activity. Protease inhibitors which did not affect signal peptidase activity also failed to inhibit amylase release from microsomes. Although the observed amylase release was in the opposite direction to enzyme secretion and involved fully-synthesised proteins, rather than nascent peptides, it is proposed that the enzyme release phenomenon reported from this laboratory (Pearce et al. (1978) Biochem. J. 176, 611–614) is related to the protein transporting mechanism involved in secretion.     

Affinity labeling of phosphoenolpyruvate carboxykinase with 1, 5-I-AEDANS.

The concentrations of zinc thionein and cytosolic zinc in rat liver were examined in male rats five days after bilateral adrenalectomy. Zinc in metallothionein increased 10 fold, as compared with control animals. Cytosolic zinc increased 79% as compared with controls. 65% of this increase could be accounted for bound to metallothionein. Sham operated animals after five days showed a 4 fold increase in hepatic zinc thionein and a 23% increase in cytosolic zinc, 71% of this increase being bound to metallothionein. Adrenalectomized rats, maintained on daily injections of corticosterone (4mg/100g b.w.), exhibited the same levels of zinc thionein and cytosolic zinc as adrenalectomized rats receiving no treatment. Adrenalectomized rats, maintained on daily injections of aldosterone (5μg/100g b.w.), exhibited the same levels of zinc thionein as the sham operated rats, but the cytosolic zinc remained elevated at the level found in adrenalectomized rats receiving no treatment. These results indicate that there is adrenal involvement in the control of hepatic zinc and zinc thionein levels in the rat.     

Plasma lipid peroxidation and erythrocyte antioxidants status in workers exposed to nickel

The objectives were to investigate the plasma lipid peroxidation and erythrocyte antioxidants status in workers exposed to nickel. The study groups comprised 69 nickel plating workers and 50 office workers residing in the same city, but away from the place of work of the study group subjects, considered as control group. Urinary nickel concentration was determined by graphite furnace atomic absorption spectrophotometry. The plasma lipid peroxidation and erythrocyte antioxidants were measured by spectrophotmetric methods. The plasma lipid peroxidation level was significantly increased in nickel-platers and their helpers as compared with controls. Erythrocyte antioxidants were significantly decreased in the nickel-platers compared with the controls. The level of plasma lipid peroxidation was positively and erythrocyte antioxidants were negatively and significantly correlated with the urine nickel levels. Multiple regression analysis assessed the oxidative stress associated with nickel and other potential confounding factors such as body mass index, the consumption of green vegetables, coffee, tea, smoking and alcohol consumption. Analysis showed that the lifestyle confounding factors: the consumption of green vegetables, smoking and alcohol, were not significantly associated with oxidative stress. The exposure to nickel, body mass index and coffee consumption were significantly associated with oxidative stress. The results show that the increased plasma lipid peroxidation and decreased erythrocyte antioxidants levels observed in nickel-exposed workers could be used as biomarkers of oxidative stress.