Fate of the Benzene Ring of Linear Alkylbenzene Sulfonate in Natural Waters

The biodegradability of linear alkylbenzene sulfonate (LAS) was studied in water samples collected from a receiving stream at locations above and below the discharge of a municipal wastewater treatment plant. Rates of primary biodegradation were determined for a commercial LAS mixture by a modified methylene blue-active substance method. Rates of LAS ultimate degradation were determined by radiochemical methods, using a C₁₂ LAS homolog uniformly labeled with ¹⁴C in the benzene ring. The C₁₂ LAS was tested at low concentrations (50 and 500 μg/liter) comparable to those existing in the receiving stream. Loss of methylene blue-active substance response over time occurred rapidly in water samples containing sediment collected from below the treatment plant, with an estimated half-life for LAS of 0.23 days. Evolution of ¹⁴CO₂ during mineralization of the benzene ring occurred rapidly in the same samples, with a half-life for the benzene ring of 0.73 day. Mineralization of the benezene ring was also observed in river water containing no sediments and in river water and sediment samples collected from above the treatment plant. However, the rate of degradation was reduced in these cases, with half-lives for ring carbon ranging from 1.4 to 14 days. Although LAS degradation was enhanced in the presence of sediments, adsorption of LAS to the clay-silt fraction of river sediments was low, and most of the radioactivity was bound to biomass.     

Structural and genetical studies on the high-molecular-weight subunits of wheat glutenin

Summary The high-molecular-weight (HMW) subunits of glutenin from about 185 varieties were fractionated by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). About 20 different, major subunits were distinguished by this technique although each variety contained, with only a few exceptions, between 3 and 5 subunits. Further inter-varietal substitution lines to those already described (Payne et al. 1980) were analysed and the results indicate that all the HMW subunits are controlled by the homoeologous group 1 chromosomes. All hexaploid varieties studied except ‘NapHal’ contained two major subunits controlled by chromosome 1D. Their genes were shown to be tightly linked genetically for only four different types of banding patterns were observed. The nominal molecular weights determined after fractionation in 10% polyacrylamide gels were between 110,000 and 115,000 for the larger of the two subunits and between 82,000 and 84,000 for the smaller. One quarter of the varieties contained only one major HMW subunit controlled by chromosome 1B whereas the rest had two. The chromosome 1B subunits were the most varied and nine different banding patterns were detected. All the subunits had mobilities which were intermediate between those of the two chromosome 1D-controlled subunits. Only two types of HMW subunit controlled by chromosome 1A were detected in all the varieties examined; a single variety never contained both of these subunits and 40% of varieties contained neither. The chromosome 1A-controlled subunits had slightly slower mobilities in 10% gels than the largest HMW subunit controlled by chromosome 1D. About 100 single grains were analysed from each of five different crosses of the type (F₁ of variety A × variety B) × variety C. The results indicate that the genes on chromosome 1B which control the synthesis of subunits 6, 7, 13, 14 and 17 are allelic, as are the genes of the chromosome 1A-controlled subunits, 1 and 2.     

On the purification of nitrite reductase from Thiobacillus denitrificans and its reaction with nitrite under reducing conditions.

Nitrite reductase (cytochrome $\text{cd}$) from $\text{T. denitrificans}$ has been crystallized in high yield in three simple and rapid steps. The spectral absorption ratio at 408 to 280 nm was 1.52. Light absorption spectra in the oxidized and reduced states were virtually identical to those of nitrite reductase from $\text{P. aeruginosa}$. EPR spectroscopy of nitrite reductase at 12° showed a low-spin ferric heme resonance with g-values at 2.52, 2.45 and 1.73 assigned to the d-heme. Reaction of nitrite reductase with nitrite in the presence of the reducing systems [(ascorbate + PMS) or sulfide] resulted in the formation of nitric oxide (confirmed by gas chromatography) which reacted with both $\text{c}$- and $\text{d}$-hemes of nitrite reductase yielding an EPR-detectable enzyme-NO complex with g-values at 2.07, 2.04 and 1.99 and a ¹⁴N hyperfine splitting constant of 22.5 gauss. The amount of nitric oxide produced enzymatically with sulfide as electron donor was only 5% of that found when ascorbate plus PMS served as reductant.To our knowledge the detection of the unique enzyme-NO complex is the first definitive EPR evidence for the mandatory liganding of nitric oxide with pure nitrite reductase during nitrite reduction.     

Inhibition of methanogenesis in salt marsh sediments and whole-cell suspensions of methanogenic bacteria by nitrogen oxides.

Hydrogen-dependent evolution of methane from salt marsh sediments and whole-cell suspensions of Methanobacterium thermoautotrophicum and Methanobacterium fornicicum ceased or decreased after the introduction of nitrate, nitrite, nitric oxide, or nitrous oxide. Sulfite had a similar effect on methanogenesis in the whole-cell suspensions. In salt marsh sediments, nitrous oxide was the strongest inhibitor, followed by nitric oxide, nitrite, and nitrate in decreasing order of inhibition. In whole-cell suspensions, nitric oxide was the strongest inhibitor, followed by nitrous oxide, nitrite, and nitrate. Consideration of the results from experiments using an indicator of oxidation potential, along with the reversed order of effectiveness of the nitrogen oxides in relation to their degree of reduction ,suggests that the inhibitory effect observed was not due to a redox change. Evidence is also presented that suggests that the decrease in the rate of methane production in the presence of oxides of nitrogen was not attributable to competition for methane-producing substrates.     

13C NMR spectroscopy of labeled pyridoxal 5'-phosphate. Model studies, D-serine dehydratase, and L-glutamate decarboxylase.

Pyridoxal 5'-phosphate labeled to the extent of 90% with 13C in the 4' (aldehyde) and 5' (methylene) positions has been synthesized. 13C NMR spectra of this material and of natural abundance pyridoxal 5'-phosphate are reported, as well as 13C NMR spectra of the Schiff base formed by reaction of pyridoxal 5'-phosphate with n-butylamine, the secondary amine formed by reduction of this Schiff base, the thiazolidine formed by reaction of pyridoxal 5'-phosphate with cysteine, the hexahydropyrimidine formed by reaction of pyridoxal 5'-phosphate with 1,3-diaminobutane, and pyridoxamine 5'-phosphate. The range of chemical shifts for carbon 4' in these compounds is more than 100 ppm, and thus this chemical shift is expected to be a sensitive indicator of structure in enzyme-bound pyridoxal 5'-phosphate. The chemical shift of carbon 5', on the other hand, is insensitive to these structure changes. 13C NMR spectra have been obtained at pH 7.8 and 9.4 for D-serine dehydratase (Mr = 46,000) containing natural abundance pyridoxal 5'-phosphate and containing 13C-enriched pyridoxal 5'-phosphate. The enriched material contains two new resonances not present in the natural abundance material, one at 167.7 ppm with a linewidth of approximately 24 Hz, attributed to carbon 4' of the Schiff base in the bound coenzyme, and one at 62.7 Hz with a linewidth of approximately 48 Hz attributed to carbon 5' of the bound Schiff base. A large number of resonances due to individual amino acids are assigned. The NMR spectrum changes only slightly when the pH is raised to 9.4. The widths of the two enriched coenzyme resonances indicate that the coenzyme is rather rigidly bound to the enzyme but probably has limited motional freedom relative to the protein. 13C NMR spectra have been obtained for L-glutamate decarboxylase containing natural abundance pyridoxal 5'-phosphate and 13C-enriched pyridoxal 5'-phosphate. Under conditions where the two enriched 13C resonances are clearly visible in D-serine dehydratase, no resonances are visible in enriched L-glutamate decarboxylase, presumably because the coenzyme is rigidly bound to the protein and the 300,000 molecular weight of this enzyme produces very short relaxation times for the bound coenzyme and thus very broad lines.     

Cytological detection of poly (ADP-ribose) polymerase

An attempt was made to demonstrate poly (ADP-ribose) polymerase cytologically. In vitro incorporation from the nucleotide, [³H]NAD was detected in frozen sections of onion embryo and meristematic tissue by autoradiography. In meristematic tissue, there was a correlation between the number of cells displaying intensein vitro incorporation from [³H]NAD and cytological DNA polymerase activity. Performed enzymes effecting a distinct incorporation from [³H]NAd were localized in the nuclei of all tissues of the ungerminated seed except the endosperm. Evidence for poly (ADP-ribose) polymerase has been obtained for the first time from higher plant cells and localized cytologically.     

Physiological and biochemical effects of the mycotoxin patulin on Chang liver cell cultures.

Patulin exhibits both cytotoxic and cytopathic effects on cultured Chang liver cells. The LD50 found was 1.85 mug per ml of patulin. Effects on growth were observed with as little as 0.1 mug per ml of patulin; a 50% reduction in growth was observed at 0.38 mug per ml of patulin. Using a challenge dose of 2.5 mug per ml of patulin, the cytotoxic effect was reversible after an exposure of 10 min, but was not reversible after 20 min. Protein synthesis was depressed after 60 min and RNA synthesis after 20 min of contact with patulin. Neither protein nor RNA synthesis was completely inhibited after 260 min.     

Hormonal changes around bovine luteolysis.

Plasma concentrations of estradiol-17beta, progesterone, LH and 13, 14-dihydro-15-keto-PGF2alpha were determined by radioimmunoassay on 2-hourly samples obtained around luteolysis and estrus in three dairy cows. The decline in progesterone occurred before the preestrous rise in estrogen and no pre-estrous peak of progesterone could be detected. The major activity of prostaglandin coincided, with declining progesterone levels and the active stage of estrogen secretion.     

The evolution of virus-induced apoptosis.

Viruses from several different families are able to exploit their host''s cell death programmes so as to maximize viral fitness. Consideration of the evolution of such strategies has lead to the suggestion that the virus should inhibit apoptosis, in order to prolong the life of the cell and thereby maximize the number of progeny virions. The host, on the other hand, should stimulate apoptosis thereby inhibiting viral growth and blocking viral spread. For example, the function of the latent membrane protein I (LMPI) of the Epstein-Barr virus and the bcl-2 homologue gene A179L of African swine fever virus is to inhibit apoptosis. However, in other cases it is the virus that stimulates cell death or the host that benefits from inhibiting apoptosis, such as in fatal alphavirus encephalitis. This has been explained by assuming that virus-induced apoptosis in non-regenerating cells would be detrimental to the host. We present a mathematical framework for understanding virus-induced apoptosis which accounts for these two opposite solutions to virus infection with respect to the mode of virus replication and the life cycle of the target cell.